Rich Roll (4:10)

The Rich Roll Podcast hey everybody. Welcome to the podcast. Good to be here. Glad to have you. So, a couple days after I sit here recording this, I'm undergoing back surgery and I'm going to be laid up recovering for about three weeks or so, which obviously interferes with the cadence of recording new episodes. And this plus my normal stash of episodes that we have kind of in the hopper is a little bit thinner than usual by dint of my focus having been placed more and more recently on writing a book. But the show must go on. And it will go on. But right now, in order for it to go on, my health demands for a couple taps into the archive. Well, to resurface a couple great past episodes that maybe you missed or skipped over so that I can take a break, a much needed break, and release a little bit of pressure to prematurely return to recording before I am adequately healed. So this is an episode that I re listened to recently and found just as profound as I did the first time around and therefore I think worthy of your attention if you missed it when it first published over three years ago, but equally so even if you did catch it upon its initial release. All of which is to underscore just how important the topic of this conversation happens to be. That topic being, of course, sleep. Sleep is essential to not just feeling good and energetic, but absolutely mission critical to every facet of well being, from recovery and performance, of course, but also mental acuity, memory and longevity, and even for staving off lifestyle illness and diseases of physical and mental decline. But why is sleep important? What exactly is it doing for us? What happens when we don't get enough of it? And what exactly should we all be doing to prioritize and improve it? Well, there is nobody more well suited to answer all of these questions than today's guest, the fascinating Dr. Matthew Walker. Dr. Walker is the author of the mega bestselling book why We Sleep. He's a professor of neuroscience and psychology at the University of California, Berkeley, and he is the founder and director of the center for Human Sleep Science. Matt has this really interesting, rather ebullient way of drawing you in to what he has to say that I have to say is rather spellbinding. And what he has to say is point blank vital for everyone to hear. So if you're someone who hasn't thought that much about sleep, someone who thinks they'll sleep when they're dead, or someone who struggles with sleep, or if you're one of those people who prides themself on not needing much sleep, or perhaps you're just someone who struggles to focus and feels off more than on. Well, if you find yourself falling into any one of those categories, then this one, my friends, just might be the most important thing you listen to this year. So with that, I give you me and Dr. Matthew Walker. Well, Matthew, so delighted to have you here. People who listen or watch this show know well my level of obsession with sleep. I'm going to try to refrain from making it basically an indulgent referendum on my sleep peccadillos.

Matthew Walker (7:42)

That's great.

Rich Roll (7:42)

I'm sure I will diverge into that at some point because I think it's instructive. But I've been looking forward to this for a very long time. A huge fan of the work that you do, and it's just a pleasure and an honor to have you here today.

Matthew Walker (7:53)

Well, it's a privilege and a delight to be sitting across from you and longtime listener as well. So thank you for all that you do.

Rich Roll (8:00)

Yeah, absolutely. I want to kick off with this. One of the super interesting hypotheses in the book that you purport is this idea that sleep evolved before the brain, hence before wakefulness. So the lens through which we think about sleep is sort of in reverse. Right. The question shouldn't be why do we sleep? The question is really why are we awake? Right. And whether or not that's true, I think it's super interesting and instructive to kind of shift that lens. And when you think about it from that perspective, everything seems a little bit different.

Matthew Walker (8:35)

Yeah, it isn't. And I have no good sound evidence for that theory right now. But I think from an evolutionary perspective, the first thing which perplexes me is the idiocy of sleep. You know, when you think of sleep from an evolutionary perspective, firstly, you're not finding a mate, you're not reproducing, you're not caring for your young, you're not foraging for food, and worst of all, you're vulnerable to predation. So on any.

Rich Roll (9:03)

Not only that, you're an insane person, right? You go through this whole thing, like if you were awake and you were experiencing the states that you experience when you're asleep, you would be institutionalized.

Matthew Walker (9:12)

That's right, yeah. And that's what we call dream sleep, which seems to be normal. But you know, on any one of those grounds, sleep should have been strongly selected against in the course of evolution. But the fact that sleep has fought its way through along every step of the evolutionary pathway. In fact, if we look back, we can even find sleep like states in earthworms, which are ancient from an evolutionary perspective. So in other words, sleep evolved with life itself on this planet, and then despite all of those trappings, it fought its way through heroically every step along the evolutionary pathway. In other words, if sleep doesn't serve some absolutely vital set of functions, it's probably the biggest mistake that the evolutionary processes has ever made. And we've now realized that it didn't make a spectacular blunder. But that premise that sleep evolved is usually founded on the idea that we were awake and then we evolved to sleep. And one thought that crossed my mind, and I was perhaps stupid enough to write it in the book, I wonder if it's the other way around. Why did we assume that we evolved sleep? Why don't we assume that sleep is the de facto state of all birth life on planet Earth, and it's from sleep that wakefulness emerged and evolved. Now, shy of a time capsule or some serious smelling salts, I'm probably not going to be able to go back and figure that out. But I think it's an interesting sort of way to.

Rich Roll (10:50)

Well, the evolutionary advantage of wakefulness is self evident, right? We need to procreate, we need to feed ourselves. But less obvious is the evolutionary advantage of sleep. It just strikes us as being something that gets in the way as opposed to crucial for all the functions that you kind of go through seriatim in the book.

Matthew Walker (11:09)

And I think that's perhaps one of the reasons that people are so misunderstanding of sleep and so understandably neglecting of sleep. Because most people, if you didn't understand what sleep is, you would think, well, my body gets some rest and my mind is dormant. And nothing could be further from the truth. There is an immense cascade of health benefits, this constellation of nighttime gifts that sleep will provide to your body and every operation of the mind that we know is overhauled. Some spectacular things. In fact, during certain stages of sleep, your brain is up to 30% more active than when you're awake. And so it's so understanding that we would think, well, you know, if I didn't know anything about sleep, surely I can just shave off an hour here or two. And it. It just doesn't work like that. You know, one hour. We can think of this incredible global experiment that's performed on well over 2 billion people across 70 countries twice a year. It's called daylight savings time. And what we've discovered is that in the spring, when we lose just one hour of sleep, there is a 24% increase in heart attacks the following day.

Rich Roll (12:32)

So crazy.

Matthew Walker (12:33)

Yet in the fall, and then the.

Rich Roll (12:34)

Reverse of the fall. Exactly.

Matthew Walker (12:35)

You sort of see, I think it's a 21% reduction in heart attack. So that's how fragile.

Rich Roll (12:42)

And yet if everybody was sleeping eight hours a night, it would be irrelevant. Right. So it's less about daylight savings time than it is about our social constructs around when we need to get up and go to work or go to school.

Matthew Walker (12:53)

That's right, yeah. I think, you know, society has firstly stigmatized sleep with this label of laziness that if you're getting sufficient sleep, you're maybe slothful. And sometimes when I'm at speaking events, people will come up and they'll usually wait right until the end of the line of questions, and they'll whisper sort of to me, look, I'm one of those people who needs, gosh, probably about eight hours of sleep. And as if the worst secret, the most shameful thing that you could ever suggest. So I think that's the first issue. But then we're working longer hours, and pre pandemic, you know, commuting times had also increased. And when you think about that, so we're leaving the house earlier, we're arriving home later, you know, no wants to shortchange on time with family or Netflix or whatever it is. And so the one thing that gets squeezed like vice grips in the middle of the night is this thing called a full night of sleep.

Rich Roll (13:59)

Yeah, you're almost some kind of punk rock revolutionary if you protect your sleep time. Right. It is the one thing that's negotiable or dispensable when you're looking at how you allocate your time?

Matthew Walker (14:10)

That's right. It seems to be. And of course the reality is that sleep, alas, is not an optional lifestyle luxury. It's a non negotiable biological necessity. It is your life support system.

Rich Roll (14:25)

Well, we all know the people who say, I only need four hours or I'm fine on five hours. And I think you have, I've heard you say something along the lines of 0% of people need less than X number of hours. That's all a story that people tell themselves, but it's simply not the case.

Matthew Walker (14:44)

That's right, yeah. So I think if you look at the weight of the evidence, the number of people who can survive on five hours of sleep or less without showing any impairment, rounded to a whole number and expressed as a percent of the population is zero. And it's. To me you would ask the question, well, why do people think that they're doing okay? And what we've discovered is that your subjective sense of, of how well you're doing when you are insufficiently slept is a miserable predictor of objectively how you're doing when you're insufficiently slept. And so, you know, it's a little bit like a drunk driver at a bar. You know, they've had six or seven shots and they pick up their car keys and they say, look, I'm fine to drive home. And your response is, I know that you think you're fine to drive home, but trust me, objectively you're in no state. And it's the same way with a lack of sleep. So that's one of the, the sort of, the frightening aspects of insufficient sleep that you think you're doing just fine. And gradually over time, that deficient form of you becomes the new norm. And most people don't go from sleeping eight hours down to five hours. It's this sort of gradual chipping away at their sleep time and they don't realize the version of themselves. And a great example of this clinically is in sleep disorders such as sleep apnea. And these patients will say to you, look, doc, I think I'm fine, I think I'm doing pretty well. And then you treat the sleep apnea. So they start sleeping better, they're not snoring, they're not gasping for breath, and within a few weeks they cannot believe the transformed state of themselves. I had one patient who said, you know, it was as though with the sleep Apnea device. I'd come along and I'd wiped a frosted window clear and finally I could see again. Wow. And that's the type of mental benefit that you get. And of course, physiologically, it's amazing.

Rich Roll (16:48)

Yeah, yeah, yeah. I mean, I just know, you know, when you're younger, sleep comes easy. As you start to age, it becomes a little bit more fragile and elusive and I found myself having to really be much more intentional about it. And the difference between having a good night's sleep where I get my eight hours and you know, I know that I've been in a sufficient amount of REM state and NREM deep state, all of that, my whole experience of my life is completely different from those nights where I struggle and wake up and had maybe six and just not so good. Like everything from, you know, mentally, emotionally, physically, product, productivity wise, like every single. There is nothing that is not positively impacted by having a really good night of sleep. And yet it's for me, we'll get into this later. But you know, replicating that day in, day out becomes tricky.

Matthew Walker (17:41)

Yeah. And it is a hard thing, you know, and I think one of the lessons I learned from publishing the book, you know, at the time, I, I think the book came out in 2017 and I. It took about four years to write. So prior to that, sleep was really the neglected stepsister in the health conversation of today. And I was so upset by the suffering that was happening in society caused by this global sleep loss epidemic. And as a consequence, you know, I was almost a little bit heavy handed, I think, in sort of dishing out some of these facts. And I have, to be honest, I have to speak the truth of the science as well. But for certain people, that almost made them sort of more anxious, you know, particularly for people with insomnia who of course would come to a book called why we sleep. The book wasn't called how to cure your insomnia, but I'm sure, of course they're still going to buy that book. And I think I learned my lesson to offer some kind of preface regarding that this book is going to be very triggering and challenging if you don't sleep well. And therefore when you're not daisy chaining those nights of good sleep just as you're describing night after the night. And you understand the detriments of sleep, it can be concerning. And I'm the worst for that, you know, just like you. I can't string it together now I'm getting older. I'm, I'm well in the Foothills of middle age.

Rich Roll (19:10)

Fabulous, by the way.

Matthew Walker (19:12)

Thank you. I just turned 70 the other day, so it's great. But, you know, I think it's that I feel that anxiety. And for me it's terrible because I'm lying in bed awake. I'm realizing that, you know, my dorsolateral prefrontal cortex is not shutting. I'm not releasing this neurochemical. My cardiovascular system is going to be this. My immune system. And at that point, you know, you're dead in the water for the next chance. So you become the sort of like the Woody.

Rich Roll (19:38)

Ellen, you're the guy. Like I'm the guy who's supposed to have this figured out.

Matthew Walker (19:41)

That's right. Yeah. And that just shows you that, you know, even if you have, you know, all of this knowledge, you know, biology can still teach you a few lessons.

Rich Roll (19:50)

Right. Well, there's so many directions I want to take this, but I think it probably would be wise to just spend a few minutes talking about, like, sort of defining our terms. Like, what is sleep like going through the various stages and kind of explaining the terrain.

Matthew Walker (20:05)

Yeah. So sleep in humans at least, and most mammals and birds is broadly separated into two main types that you'd mentioned. On the one hand, we have non rapid eye movement sleep or non REM sleep for short. And non REM sleep has been further subdivided into four separate stages, in fact, unimaginatively called stages one through four. We're a creative bunch, clearly, as sleep researchers decreasing in their depth of sleep. So stages three and four are those really deep stages of restorative sleep. That's what your sort of sleep tracker would say. That's deep sleep. Stages one and two, they're light sleep. And then on the other hand, we have rapid eye movement sleep or REM sleep, named not after the popular Michael Stipe band for the 1980s, but after these strange horizontal shuttling eye movements that occur under the eyelid as you're in this stage. And REM sleep is the stage during which we principally dream. And that's where you have your most sort of florid, most narrative, hallucinogenic, emotional sort of dreams. And it turns out that those two types of sleep, non REM and rem, will play out in this incredible battle for brain domination throughout the night. And that sort of cerebral war is going to be won and lost every 90 minutes and then replayed every 90 minutes, at least in humans. And that creates this standard cycling architecture of sleep. What's fascinating, though, and we actually still don't quite understand why, is that the ratio balance of those two types of sleep, non REM and REM, changes across the night. And what I mean by that is in the first half of the night, the majority of those 90 minute cycles are comprised of lots of deep non REM sleep but very little REM sleep. And so as you push through to the second half of the the night now that seesaw balance will actually shift and instead you get much more rapid eye movement sleep, particularly in the last couple of hours. And it's not just important to sort of understand one's sleep, but understanding that structure has implications real life. So let's say for example, that I normally get my eight hours sort of, and it doesn't, you know, we can speak about timing on the clock face and what makes sense for people, but. So let's say that I'm a guy who goes to bed at 10 and I typically wake up at 6, but today I've got an early morning meeting or I want to sort of cut my sleep short to get a jumpstart on the day to get to the gym and I wake up two hours early. So I wake up at four rather than six. How much sleep have I lost? Well, I've lost two hours from eight hours. So I've lost 25% of my sleep. Well, yes and no. Yes, I've lost 25% of my total sleep. But because REM sleep comes late in the morning, I may have lost 50, 60, maybe even 70% of all of my REM sleep. So it's not just sort of, you know, academic to understand. Even though it's fun for me, but for many people it does have real world implications.

Rich Roll (23:25)

The complexity of it is fascinating. I mean sleep really is right up there with outer space in the depths of the ocean in terms of its it's mysteries and the idea that we're just beginning to learn what's actually going on. And it's not a matter of. I'm sure you get this question all the time like, well, what's more important, REM sleep or non REM sleep? Or what's the sort of significance of being deprived of one over the other, but it's really the interplay of all of these things and the more complex you realize it to be, it becomes impossible to consider that it's not crucial to all facets of human health.

Matthew Walker (24:03)

That's right. And you know, when we go back to that evolutionary story of how, you know, detrimental sleep is as a state and it is, let's face it, you know, if there were any stage of sleep that were not important, that Mother Nature could have come in and excised and had you doing all of these benefits of wakefulness that you just. I'm quite sure she would have. And what we've learned is that every stage of sleep is important. Different stages of sleep perform different functions for the brain and body at different times of night. And so, yeah, I often get that question. People will say, how can I get more deep sleep? Or how can I get more REM sleep? And, you know, I often say, well, why do you want more of that? And they say, well, isn't that the good stuff? And they're both absolutely critical. Now, I could make a scientific argument that REM sleep could be a little bit more important from a simple mortality state, because there were studies done back in the 1980s with rats and they've actually never been replicated. Again, I found them difficult to read. I do research in humans, I don't do animal research, and I think they won't be replicated for good reason. What they wanted to do is see if a lack of sleep is deathly. Is a lack of sleep fatal? And they had three different flavors of the experiment. In the first, they took rats and they just deprived them of sleep, you know, night and day after day, night and day after day. And what they found is that those rats died within about 20 days. So in other words, rats will die as quickly from a lack of food as they will from a lack of sleep. That's how fundamental it is. Then the two additional flavors of the experiment, they selectively deprived them of either just rapid eye movement sleep so that they could get just non rem, or they did the opposite. They just deprived them of non REM and gave them rem. And firstly, both of those were fatal. But what was interesting is that the rats died from REM sleep deprivation within about 30 to 40 days, and they died from deep non REM sleep deprivation within about 50 or 60 days. So if we want to sort of do a Coke Pepsi challenge between sort of, you know, non REM and rem, which one wins out in the mortality battle? It seems to be REM sleep. And to me, that's interesting too. If you'd asked me where I would place my bets, I would have said non rem. The reason is because non REM came first. If you look during sort of the time course of evolution across phylogeny, non REM sleep was the first sleep to emerge. And it was only when we went from reptiles, amphibians and fish, and then there was that bifurcation to birds and then mammals did the evolution of REM sleep emerge? So REM sleep is the new kid on the evolutionary block. And furthermore, REM sleep evolved twice independently in birds and mammals, which I find is fascinating, too. So to come back to your point, I'm sorry, I'm drifting, but all stages of sleep are critical. No one stage of sleep you can do without without suffering detriment.

Rich Roll (27:25)

Right. It is fascinating that sleep deprivation is fatal. And you talk about this in the book. There used to be, before they were outlawed, these contests. People would see how long they could go without sleep. And there's one case study that I recall from the book where the guy went mad, and then literally, I don't know how long it took him, like 10 days or something like that before he passed away.

Matthew Walker (27:47)

Well, there were two things. Firstly, you write that Guinness, the World Book of Records, used to recognize record attempts at insufficient sleep. And then, as the evidence mounted as to how deleterious a lack of sleep is, they found it medically impossible to recognize and ethically impossible to recognize. So Guinness no longer recognizes any attempt to break the world record for a lack of sleep. And to put that in context, we think of Felix Baumgartner, that incredible Austrian who went up in the Red Bull sort of space capsule, as it were. And when he ascended the outer atmosphere of the planet, he opened up his door and he leapt out, and then he hurtled back down to Earth, and I believe he broke the sound barrier with his own body. Now, Guinness says that's fine, but depriving yourself of sleep? No, no, no. That's the relative sort of aspect that we're thinking about. There was a famous case of a radio disc jockey in New York in the 1950s called Peter Tripp, and he wanted to try and break the world record, which was going eight days straight without sleep. And he was doing this for the March of Dimes. And he would sort of sit in Times Square and he was going to do this play his, spin his records. And after three days, he was hallucinating and he was psychotic. After five days, he believed that people were trying to poison him and that the Secret Service was coming to get him. And then he did apparently break the world record. He went eight days straight without sleep. And then he slept for a little over 20 hours. He woke up, he ordered his papers, had his breakfast, and people said, oh, it seems to be back to normal. But Tripp was no longer Tripp after that. He started to have problems at work. He got caught up in what was called the payola scandal, where people were sort of paying DJs under the desk to play their tracks. His marriage fell apart and the last people heard was that he was selling books door to door in the Midwest.

Rich Roll (29:56)

Wow. And so you're attributing that to this crazy experiment that he did?

Matthew Walker (30:00)

Well, that was the belief. Now other people, I should note, have gone past his level of sleep deprivation. And although they went through the same experience during the lack of sleep psychosis, memory loss, emotional instability, they seem to go back to normal. So I think what's happening here, and I'm sure we'll come on to sleep and mental health at some point is in those people who are in that vulnerable range where they haven't crossed the threshold of mental ill health, but they're right there. And anything that pushes them past it, be a traumatic event, be it a difficult divorce or a long stretch of no sleep, can actually pull that trigger and send them over that sort of teetering precipice down into a state of prolonged mental ill health.

Rich Roll (30:47)

Right. That's wild. But those are kind of fringe cases in the sense that people are doing this wacky kind of thing. But the more relatable prevalent situation is chronic sleep deprivation, which I don't know what the statistics are. I'm sure you do. Of how many people just on a day in, day out basis are not getting enough sleep and how that plays out long term in terms of their physical, mental, emotional health.

Matthew Walker (31:14)

Yeah, it's quite shocking. And I guess this is sort of the insomnia disclaimer if you prefer to sort of listen away. But firstly, what we know is that one out of every three people that you pass on the street is not getting the sleep that they need. So the CDC right now recommends, stipulates a minimum of seven hours of sleep to maintain human health. And it doesn't, as you said, most people are not pulling all nighters frequently or trying to break world records, but it doesn't take that. You know, we've already mentioned the daylight savings experiment. I'll just give you a few other examples. If I take a healthy young male and I limit them to let's say four or five hours of sleep for a couple of nights, their level of testosterone drops to someone who is 10 years their senior. So a lack of sleep, well, age a man by a decade in terms of that critical aspect of wellness and virility. And we see equivalent impairments in female reproductive health, by the way, follicular stimulating hormone, abnormal menstrual cycles, Difficulty in conceiving. So that's hormones that go awry. We also know, for example, that if I were to take you and put you on a diet of, let's just say, four hours of sleep a night for a couple of nights, at the end of those four nights, your blood sugar levels would be so disrupted that your doctor would classify you as being pre diabetic.

Rich Roll (32:38)

That's crazy.

Matthew Walker (32:39)

Which stuns me. And to induce that kind of a deficit, a 40% deficit in your sort of glucose optimization, you would have to gain about 20 pounds of obese mass within four days. Or you could do it by under sleeping. Wow. We also know, for example, that if you're not getting sufficient sleep in the week before you get your flu shot, you produce less than 50% of the normal antibody response. I'm sure we'll discuss that when we speak about immunity. There was an amazing experiment, though, done by some colleagues in the United Kingdom, and they put healthy participants through two different conditions. In one condition, they were limited to six hours of sleep a night for one week. And then they were given a full eight hour opportunity for one week. And then they measured the change in their gene activity, activity profile relative to when they were getting sufficient sleep. And there were two striking findings. The first was that a sizable and significant 711 genes were distorted in their activity caused by that lack of sleep. And this is not dramatic sleep loss. This is.

Rich Roll (33:49)

Yeah, I mean, most people say six hours. I'm good. That's pretty good, right?

Matthew Walker (33:53)

And that just doesn't seem to be the case biologically. What was also interesting, however, was that about half of those genes were actually increased in their activity, or what we call overexpressed. The other half were decreased or switched off in their activity. Now, those genes that were suppressed, caused by a lack of sleep were numerous genes associated with your immune system. Yet those genes that were actually increased in their activity were genes that were associated with the promotion of tumors, genes that were associated with cellular stress, and as a consequence, cardiovascular disease, and genes that were associated also with metabolism and changes in metabolism. And what that study taught me, at least, is that there is no aspect of our physiology that seems to be able to retreat at the sign of sleep deprivation and get away unscathed.

Rich Roll (34:49)

Yeah. One of the striking things in the book that really hit me was the relative lack of elasticity in the human body in that just one night of dysregulated sleep a week has much more of a profound deleterious effect than you would think. You would think like, well, I Sleep pretty well most nights, but once a week my stuff got screwed up, but I'll recover. But the downstream implications of just a little bit of dysregulation are much more serious than one would suspect.

Matthew Walker (35:23)

Yeah. I mean, a good example is another study where if you take healthy adults and you limit them to just four hours of sleep for a single night, the next day we see a 70% drop in critical anti cancer fighting immune cells. 7, 0 called natural killer cells. Now today, you and I have both produced cancer cells. More than likely, what prevents those cells from becoming and manifesting as the condition that we call cancer is in part these critical cancer fighting immune cells, natural killer cells. That is a dramatic state of immune deficiency. And it happens quickly after just one bad night of sleep. You know, so you could imagine the state of your immune system after weeks, if not months of insufficient sleep.

Rich Roll (36:10)

Yeah. One of the things that is very vivid in the book as well is this process that takes place when you're sleeping, this kind of detoxification process. Right. Where you're kind of cleansing the brain and washing out the beta amyloids and all the kind of negative things that accumulate in the mind throughout the day. Because wakefulness is really the toxic state. Right. And in sleep that is the restorative state, obviously. And you likened it to the island of Manhattan where all the skyscrapers shrink and like a wave washes over them and cleans all of them and all this nasty stuff that we don't want is washed away. And when you impede that process, those things start to accumulate. Right. And that's why we see so many of these downstream diseases cropping up. Everything from Alzheimer's, diabetes, cardiovascular disease, et cetera.

Matthew Walker (37:06)

Yeah. I mean, from the perspective of your brain, you know, this sounds a little bit extreme, but biologically I think it's accurate that wakefulness is low level brain damage and sleep is sanitary salvation. And this, I think is one of the most exciting areas in sleep science. Over the past five years, it's just ballooned. And we've been fortunate enough to do some of this work, which is the relationship between a lack of sleep and Alzheimer's disease. And it really has become a four part story, which is association, causation mechanism, and then treatment. Hope so. What we understood about four or five years ago is that people who are typically sleeping less than six hours a night went on to develop far more of those sticky, toxic protein elements that are the culprits underlying Alzheimer's disease called beta amyloid, and more recently this thing called tau Protein. They're the two proteins that we believe underlie the condition of Alzheimer's disease. Then what we also found is that people who have sleep disorders such as insomnia or sleep apnea, also have a significantly higher risk of going on to develop Alzheimer's disease later in life. But they're just associations, they don't prove causality. And then several years after that, scientists demonstrated that if you take a healthy adult and you deprive them of sleep for just one night, or you deprive them of just deep sleep for one night, you see an immediate escalation in that Alzheimer's protein, beta amyloid circulating in the bloodstream, circulating in the cerebrospinal fluid, and also within the brain itself, using brain imaging technology. So that proved causality, that you can take an otherwise healthy person, take away that thing called sleep, and you can trigger that instigation of what seems to be like the emergence of an Alzheimer's cascade in pathology. If that's true, then we ask the question, well, what is it about sleep that de escalates that Alzheimer's disease? Protein in the brain. And there was just, I mean, this is, I think it's Nobel prize worthy. But a researcher called Macon Nedegaard at the University of Rochester made three remarkable discoveries. She was looking at mice and what happened when they slept. And the first thing that she discovered is that the brain has a cleansing system. And we didn't think it did. Now we knew that the body had its own cleansing system, which everyone will know about, called the lymphatic system, but we didn't think the brain did. And she discovered, in fact it does have a cleansing system called the glymphatic system, named after the glial cells that make up this process.

Rich Roll (39:51)

Right. And those live in between the brain cells. Right?

Matthew Walker (39:54)

That's right. Glial is sort of, if you look at the Latin and Greek sort of derivative, the entomology is glue. Because we used to think that they were just the cells that kind of glued the actual brain cells. Well, they're all brain cells technically, but would glue the neurons together. But they are, they sort of outnumber your neurons by many fold. And they're critical, they perform lots of functions, but they form this network, this sewage system. So that was the first discovery. Then she found that that cleansing system wasn't always switched on in high flow volume across the 24 hour period. Instead, it was when those mice were asleep and when they went into deep sleep that that sewage system really kicked into high gear. The Final discovery, and that's what makes it relevant to Alzheimer's disease, is that she found that one of the metabolic byproducts, one of the pieces of metabolic detritus, that that sleep was washing away was this toxic protein of beta amyloid. And just last year, scientists in Boston actually found a very similar pulsing, cleansing mechanism in human beings. So that was a mechanism that helped us realize how this could all connect together. For me, though, it may all sound very depressing, just as you mentioned, for yourself and I experienced this, the older that we get, typically the worse our sleep, and the older that we get, the greater our risk of Alzheimer's disease. And so it may sound quite a depressing story, but I think there's a silver lining here, because unlike many of the other factors that are associated with aging and Alzheimer's disease, for example, changes in the physical structure of the brain or even changes in the blood flow dynamics of the brain, they're fiendishly difficult to treat. And in medicine, we have no good wholesale approaches. But that sleep is a missing piece in the explanatory puzzle of aging. And Alzheimer's disease is exciting because maybe we can do something about it. Perhaps what we could do is in midlife, which is when we start to see the decline of deep sleep, that's when we could intervene with optimization of sleep, with lots of different methods that are being developed. And in that way, could we bend the arrow of Alzheimer's disease risk down on itself? Could we shift from a model of what we have right now, which is late stage treatment, to midlife prevention? Going from a model of sick care to, actually healthcare? That's one of our sort of moonshot goals. I'm incredibly excited.

Rich Roll (42:29)

Yeah. Yeah. I mean, that's the holy grail, right?

Matthew Walker (42:32)

Yeah.

Rich Roll (42:33)

And I think about this all the time. When I wake up after an amazing night of sleep, and then my experience throughout the day is optimal, and then the following night, I have a degraded version of that, and I wake up and I think, why can't I just. Why can't we figure out a way to replicate this day in and day out without pharmaceutical intervention? Like, I'm trying to do all the right things, and yet it is so elusive. And part of that, yes. Is age. Because when you're a teenager, you can just, you know, fall asleep in an instant and seem to get a good night's sleep no matter what. But I'm constantly thinking about, like, how do you figure this out and master it? Because if you could, it would literally change everybody's lives.

Matthew Walker (43:14)

Yeah. And, you know, if you take the reverse of that, we know, you know, starting with this recommended sweet spot of between seven to nine hours a night, going in the downward direction. There's a very simple truth, which is that the shorter your sleep, the shorter your life. Short sleep predicts or cause mortality.

Rich Roll (43:30)

Right. Which is, which is so ironic given that, you know, the hustle culture, you know, it's all about maximizing those daylight hours. And I'll sleep when I'm dead.

Matthew Walker (43:39)

Right.

Rich Roll (43:39)

I'm just hearkening that.

Matthew Walker (43:41)

Death. Yeah, it's, it's, you know, it's mortally unwise advice, anyone who tells you that. But to me, I think, you know, sleep could be seen as the Swiss army knife of health. You know, whatever ailment that you're facing, sleep normally has a tool in the box that can help. And so for me, I think the Shangri La is perhaps less about trying to elongate lifespan than it is really about prolonging people's health span. Because when you ask most people that's what they really want when they're trying to sort of, you know, live a clean, healthy lifestyle, they don't want a life with disease and sickness. Sickness. But when you are starting to shortchange your brain and your body of sleep, that's what you're inviting, you know, and the elastic band of sleep deprivation will stretch only so far before it snaps. And if you fight biology, normally you lose. And the way you know you've lost is disease and sickness.

Rich Roll (44:38)

Yeah, the, the human hubris over all of this, though, is something to behold, because we always think we can find a, an end run around these things. And as beautiful and magnificent as the scientific method is, it tends to be very binary in its approach. Right. So if X, then Y. Controlling for variables. But when you're dealing with systems that are so complex, my sense is that oftentimes it leads to unintended negative consequences. Right. Like, take this pill and you'll sleep well. But we're not realizing or looking at all these other things that are occurring. And it isn't until much later when researchers like yourself can pull the covers on that and say, this was not such a good idea.

Matthew Walker (45:23)

Yeah, pull the covers. No pun intended.

Rich Roll (45:25)

Right, right, right.

Matthew Walker (45:26)

But I think you're right. There is a very understandable. Again, I don't want to sort of be finger wagging or chastise people. If you don't know the science of sleep, I would be just as unknowing. But it took mother nature 3.6 million years to put this essential thing called a seven to nine hour sleep need in place. To think that with hubris or arrogance that we could come along and within five or 10 years if we're sort of forcing medical residents to go through these ridiculous sort of schedules, or if you're in some other professional industry that you can just find a way to hack that system is unfortunately misfounded.

Rich Roll (46:15)

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If you use my link, you'll also get a free bottle of AG D3K2, an AG1 welcome kit, and five of the upgraded AG1 travel packs with your first order so make sure to check out drinkag1.com rich roll to get started with AG1's next gen and notice the benefits for yourself. That's drinkag1.com rich roll the stuff that you said about Alzheimer's and dementia makes a lot of sense, but how does that work with cardiovascular disease? I mean, obviously brain health is vascular health and heart health certainly is vascular health. But what is the relationship between sleep, sleep quality and taking an insurance policy out against heart disease?

Matthew Walker (51:46)

Yeah, I mean, so we, we mentioned the daylight savings time example, but more than that, we know that people who are typically sleeping less than six hours a night on average will have about a 200% increased risk of cardiovascular disease or a heart attack in their lifetime. We also know from a prospective study that came out of Harvard Medical School that, and they took a large range of people who had no pre existing signs of cardiovascular disease and then they tracked them across five or six years. And what they found is that in those people who are sleeping less than six hours a night, they had a 200 to 300% increased risk of calcification of the coronary artery. And that coronary artery, essentially that's the, you know, the corridor of life for your heart. When you hear people saying, gosh, they had a massive coronary, what they mean is that that coronary artery had become block calcification. And that's exactly what we see now. Again, this was a prospective study. No one had any signs of that before. But when you looked at that sleep, shaving, sleep coming down and down, that was the predictive factor. We also know that however, sort of turning the tables in the positive, why does sleep give you that benefit? During deep sleep, our heart rate decelerates, our vascular system, our vessels start to relax. You can think of deep sleep like the very best form of blood pressure medication that you could ever wish for. We also see that it's during that nighttime phase when we drop levels of cortisol, which otherwise if left in high concentrations as a stress related chemical, it's, it's an adaptive chemical too. We all need cortisol. But if you're just chronically high in cortisol, that is, you know, deathly for your cardiovascular system and sleep will actually ratchet down that level. Also, sleep will quiet the fight or flight branch of your nervous system. It's called the sympathetic nervous system, which I think is terribly named. It's anything but sympathetic. You know, it's agitating, it's aggravating. And it's during deep sleep that we actually Shift over from that fight or flight branch to the more quiescent calming branch called the parasympathetic nervous system. And so now we can start to understand why we see risks for heart attack, risks for cardiovascular disorder. We published a paper a couple of months ago demonstrating that short sleep, and particularly not just short short sleep, but also fragmented sleep. And this is, I think, another important point that we've learned in the most recent years. It's not just about the quantity of sleep, it's also about the quality of that sleep. And we found that people who had fragmented sleep had a higher likelihood of their blood vessels becoming hard. It's what we call atherosclerosis, the hardening of the blood vessels, which can then be a direct pathway to cardiovascular disease and heart attack as well as.

Rich Roll (54:54)

That's interesting. And is that, is there a sense of where that falls in the pecking order of importance when you compare it to nutrition or exercise or these other kind of contributing or ameliorating factors with respect to heart disease, it's just as heavier hitter.

Matthew Walker (55:13)

You know, if you look at the combination of quantity and quality of sleep and you look at the effect sizes, the, you know, it's right up there. You can almost play the game. And I don't mean to do this because I'm someone who pays. I'm very dedicated to a practice of physical activity and exercise. You know, I'm not quite at your level, but. And I eat very cleanly. I too am a vegetarian, so I respect those things because I know how utterly important they are for my health span and my lifespan. But I can do a thought experiment where I say, I take you rich roll and I'm going to deprive you of either exercise for 24 hours, of food for 24 hours, of water for 24 hours, or of sleep for 24 hours. And sleep by. There's no comparison by a country mile will dwarf the physiological and mental deficits that come by way of that. I think the only other thing that perhaps will overtake sleep is oxygen. You know, if I stop you of oxygen, you will. I hold my hands up, I lose out to oxygen.

Rich Roll (56:22)

Right, Right. But. But you've said often that, you know, when you think of the pillars of health, sleep isn't a pillar. It's the foundation upon which all these other pillars are erected, essentially. Right?

Matthew Walker (56:33)

Yeah. I used to think it was a third pillar, but then, you know, the more I've done this research over the years, the more I realized that I was wrong. It is a foundation on which those the two things said, you know, I can give you a good example. If you're trying to manage your weight, if you're trying to diet, let's say, and lose weight, but you're not getting sufficient sleep, 70% of all the weight that you lose will come from lean muscle mass and not fat.

Rich Roll (57:00)

Right. The body, when it's fatigued in that way, wants to hold on to those fats.

Matthew Walker (57:04)

Exactly. Your body becomes stingy in giving up its fat. So in other words, when you are under slept, but you're trying to watch your diet, watch what you eat, you will lose what you wanted to keep, which is muscle, and you will gain what you wanted to lose, which is fat.

Rich Roll (57:21)

Right. And on top of that, that's when those crazy cravings for terrible foods happen. Right. I just know when I'm under slept, that's when I start thinking about all these foods that I shouldn't eat.

Matthew Walker (57:32)

And it comes by way of two different routes and they're non mutually exclusive. One is a brain route, the other is a body route. What we've firstly discovered is that when you're not getting sufficient sleep, you know, be it six hours a night, five hours a night, four hours a night for several nights, there are two critical appetite regulating hormones that go awry. These hormones are called leptin and ghrelin. Leptin. I sometimes joke that they sound like hobbits, but that's just my British Tolkien obsession. But leptin is the hormone of satiety. When you release leptin, it says to your brain and your body, you're full with what you've just eaten, you don't want to eat anymore, you're no longer hungry. Ghrelin is the opposite. Ghrelin is the hunger hormone. It says, no, no, no, you're not satisfied with your food and you want to eat more. And when you are under slept, those hormones go in the opposite direction in ways you don't wish them to. Firstly, leptin, which is the satiety signal that drops away. So you lose that signal of being full and you constantly feel hungry. If that weren't bad enough by itself, ghrelin, the hunger hormone that actually increases. So now you may have eaten a standard meal that normally otherwise would have been satisfying, but it doesn't feel satisfying and you still want to eat more. And on average, people will typically eat anywhere between 2 to 400 extra calories each day under these conditions of insufficient sleep. What was also striking from these studies is not just that you want to eat more which in general you do and you want to snack more. But it's what it is that you have a craving for because when you are under slept you have this increase, a particularly a dominant increase in wanting to eat those heavy hitting carbohydrates, also sugars as well as salty snacks. All of those are foods that we know in excess will put you on a path towards this obesogenic profile.

Rich Roll (59:32)

Right. It would be interesting to take a look at whether or not the rate of people going to the drive thru increases on daylight savings. Right. On that day when everybody's lost an hour of sleep, they're a little bit more tired. I would suspect it would follow that a lot of people are, you know, hitting McDonald's on the way to work.

Matthew Walker (59:51)

I wish I could get that data. You know, I wish there was like a McDonald's app where I could look at the usage statistics and then do that sort of, you know, study. So in the body that's part of the reason, but in the brain there is also a pathway. And we did a study several years ago where we took a group of healthy adults of normative weight and we either gave them a full night of sleep or we took sleep away for a night and then we put them at same individuals. So it's the same people going through two different studies. And inside of the brain scanner we were showing them these different food items and they had to rate how desirable those food items were. And we made this a little bit more real by saying, look, at the end of this brain scan we're going to pull you out and we're going to give you one of those foods so that you have to eat it. So they're not just saying, oh, okay, I should just be good. And I know that, you know, that I should say is nice. And what we found, firstly is that people, when they were underslept, their hunger increased. Secondly, what we found is that they were rating junk foods as far more desirable as a consequence. And then when we looked at the brain scan, something fascinating happened. There were the deep hedonic emotional centers of the brain. They were revved up as a consequence of a lack of sleep. These sort of impulsive, sort of, you know, almost these addictive brain senses, in fact they are a part of the same senses that go awry in addiction. What was also interesting is that other parts of the brain, particularly a part right upstairs above your eyes in the frontal lobe, that had shut down, which normally keeps our hedonic desires in check. And as a consequence the underslept People were sort of no longer reaching for leafy greens and a handful of nuts. They were reaching for ice cream, pizzas, these salty snacks, et cetera. So it's both within your brain that explains why you know for a fact. You know, when I'm not sleeping, I'm just, I'm always hungry.

Rich Roll (61:54)

Right.

Matthew Walker (61:55)

I can never get satisfied. I can never get full. And I don't know why it is brain and body.

Rich Roll (62:00)

Well, I feel seen and heard because as somebody who's been in recovery for a long time, in an n of one experiment, I know when I'm under slept or I've had a terrible night of sleep, all of those kind of addictive compulsions. Because I have some self awareness around them. I'm able to understand that that's what's happening. But it's always been confusing that it correlates like why do I feel like acting out or eating this thing or sending the email I shouldn't send, or all of these things that happen when I'm. When I'm under slept. That's very interesting.

Matthew Walker (62:32)

Yeah, and thanks for bringing that up too, about addiction disorders. We've done a little bit of work in this area too. What we found is that when we shortchange someone's sleep, these dopamine centers within the brain that are what we think of as reward based centers. And they're the centers in the brain that addiction will hijack. Those become increased in their sensitivity. So your reward sensitivity increases, your risk taking increases, your impulsivity increases. What we know is that those people who are under slept are far more likely to develop an addiction disorder during use. We also know, and this is perhaps even stronger of a relationship when you are trying to abstain and go through recovery. Sleep is a huge predictive factor. When you're getting enough sleep, your chances of remitting and recovering are far higher than when you're not getting sufficient sleep.

Rich Roll (63:29)

Yeah, that makes sense. Well, this is a good opportunity for me to indulge you my own history here because just reading your book again and getting ready for today, I started thinking more profoundly and deeply about my own history with sleep over the years. And I had this dawning, depressing, epiphany of just, just how sleep deprived I have been up until like literally my late 30s with how I've lived my life. I mean, I, from age like 14 to 21, I was a competitive swimmer. I was waking up throughout junior high school and high school at 4:45 every day to go to swim practice for two hours. Then I Go to school, then I go to swim practice again for two more hours, do my homework, go to bed, repeat, chronically sleep deprived through those years, going to college, the same thing. And just, you know, I have memories of just sleepwalking through my life, just so exhausted, not just from the sleep deprivation, but on top of that, like very rigorous training. Right. So I literally had no energy for anything. And then around 21 is when my alcoholism really started to kick in. So for the next 15 years was a cycle, a progressive cycle, of course, of sleeping, sort of drinking to blackout, passing out, going on three day benders, and then experiencing those sleepless nights that occur in the wake of that it would take three or four days to normalize. And terrible nights of laying in bed, sweating and staring at the ceiling and unable to sleep and shaking and the whole thing, only to finally get by Wednesday, getting one good night of sleep, feeling okay, and then repeating it again. Right. And I did that for 15 years and it wasn't. I got sober at 31 and then I transferred a lot of my addictive tendencies onto workaholism, so it didn't get that much better. But looking back, it's just unbelievable how much I shortchanged myself from sleep. And I think, what is the relationship between that early sleep deprivation and my alcoholism? What is the relationship between the alcoholic sleep deprivation and my ability to be a functional human? And all I can tell you is that when I look back, I think back on those years, I can barely remember a single book that I read. I couldn't tell you anything that I learned in law school. I barely remember college. And my memory overall is not so good. It's really like unbelievable when I think about how profound that is and the impact that it's had on my life. On top of that, this is separate. But I slept, walked, like all the time when I was a kid. Ultimately I grew out of that, but I don't know how that plays into it. But when you hear that, like, what is your reaction?

Matthew Walker (66:28)

Yeah. So firstly, from the memory point that you mentioned, we know that sleep is critical for learning and memory in at least three different ways that we can speak about. But what about the long term consequences of that? Well, we have a little bit of data from the situation of airline pilots, right, who typically, you know, have to undergo jet lag, they're chronically sleep deprived. And firstly, what scientists found when they looked at matching those pilots with sort of someone of similar age, some of similar background, education, lifestyle, et cetera, et cetera, they found that parts of their brain had actually shrunk. It's what we call atrophy. They'd lost brain cells. Where had they lost brain cells? They'd lost them, particularly in the memory centers of the brain, A structure that we call the hippocampus. And the hippocampus, which sits on the left and the right side of your brain, like a long cigar shape on the, on the left and the right side. It's almost like the informational inbox of your brain. It's very good at receiving new information and memories and holding onto them. And that part of the brain had actually deteriorated because of that disrupted sleep schedule. Now you could argue, well, perhaps it's just something about bias selection that, you know, I don't know how it would be, but airline pilots, yeah, because of poor memory, they don't go into profession X, they go into. Now piloting is essential with memory. And so I don't think that's the case. But a better demonstration of that was then they looked at how long that they'd been on the job, how many years had they been going through that sort of sleep deficiency. And that predicted the magnitude of brain shrinkage, which made me think, okay, I think it's more likely that it has to do with the sleep as well. So is there a potential long term organic atrophy consequence of insufficient sleep on the brain? We seem to think that there is, yes. But again, I think I want to be really careful here and I don't want to be causing people alarm. And what I would say is that it is never too late to start sleeping better. And that's not just me sort of pulling out the pom poms and trying to be positive. We've got data. So in a series of studies and we've done a lot of work in, as I mentioned, in older adults. But if you take a group of midlife adults who are suffering from untreated sleep apnea, heavy snoring, and then you put them on treatment, which is called a CPAP machine. Cpap, the continuous positive airway pressure. And by the way, if anyone's listening to this and they think that they suffer from sleep apnea or they have a partner who does, please go and get diagnosed. It is a deathly disease, untreated. And what they found is that about half of those participants complied to the treatment and about half didn't. And they tracked them over a 10 year period. And what they found is that those individuals who complied to the treatment and whose sleep was improved as a consequence, they staved off the onslaught of Alzheimer's disease and cognitive decline by anywhere between 10 to 15 years relative to those who remained untreated or uncompliant with their treatment. In other words, even in midlife, there is evidence to say it's never too late to start sleeping.

Rich Roll (69:44)

But can those, those brain centers that, that have atrophied be regenerated or is that a permanent thing?

Matthew Walker (69:50)

We don't know. And it depends on what extent of atrophy we do. We used to think maybe 30 years ago that the brain didn't produce new brain cells once it had matured. And once you were an adult, that was your sort of smorgasbord of brain cells. And as you lost them through time, you never got.

Rich Roll (70:11)

When you drink, you kill brain cells. They never come back.

Matthew Walker (70:13)

They never come back. Well, that's not true. There are in many regions of the brain that is true, but there are a couple of regions that it's not true. And in fact these memory centers, the hippocampus, that's one of the centers that does actually seem to have some degree of regenerative capacity, you know, how capable of meeting the demands of brain atrophy and damage. That that system is of regeneration is unclear. What I should note, by the way, is that that system of the creation of new brain cells, it's what we call neurogenesis, which I think is a great alternative name for a band rather than just Genesis. Phil, if you deprive a rat of sleep, it fails to have the regulation of that neurogenesis, you lose the capacity for neurogenesis when you are under slept. So it becomes this self fulfilling, negative vicious cycle of prophecy that if you are not getting sufficient sleep, those brain cells start to deteriorate and atrophy. And then the one thing that could help you get them back is the one thing that you keep depriving yourself of. So you lose even the salvation of the sort of. The salvaging, sorry I should say of that.

Rich Roll (71:22)

Yeah, wow. You mentioned pilots traveling from time zone to time zone. On top of that, I want to talk about the medical profession because herein lie the greatest irony. These people who are dispatched with tending to our health have this complete myopic perspective when it comes to prioritizing sleep in their own profession. And there's this systemic, you know, kind of infrastructure set up that prioritizes lack of sleep. These residents who have to work these 30 hour shifts, this legacy of an old tradition that was set in stone long ago and continues like unbelievably to, you know, be the standard operating procedure today, which is unbelievable. And I loved how you told the history of this. This guy Halstead. Right, yeah. Who. Who basically was a hard ass back at the turn of the century and just said, this is the way we're gonna do it. And today we still do it in the manner that he kind of established back then, but it turns out he was like a raging cocaine addict.

Matthew Walker (72:30)

That's right, yeah. So William Halstead was the guy who set up the first resident training program in the United States at Johns Hopkins University. And it's called a residency for a reason, because you're going to become a resident, you're going to live in the hospital.

Rich Roll (72:47)

Right.

Matthew Walker (72:48)

And he was known for being able to go these heroic long stretches without needing sleep. People were stunned. And he expected his junior residents to match him in that. And gradually after his death, it emerged the reason why he was able to do that. Halstead, in his early career, was actually studying the anesthetic properties of cocaine. And unfortunately, he started to use cocaine himself, and he became an accidental addict. And that was how he was able to just go days straight.

Rich Roll (73:27)

Right.

Matthew Walker (73:28)

Without seemingly, you know, needing sleep and.

Rich Roll (73:31)

Apparently set the expectation that everybody else should be able to manage it the.

Matthew Walker (73:36)

Way that he was, to go the same degree. Now, there were times, there were stories where people would say, you know, he would. In the operating theater, he would have to go and take a break because he was saying he was not feeling well, he was sweating a lot, he seemed to be cold, and he would have to go take a break. And, you know, because he was detoxing during the long surgery, so he had to go and administer again. And he knew that he was an addict and he sought to go into rehab under a different surname. And at the time, they were treating cocaine addiction with morphine. And unfortunately, what happened is that he came out of that rehabilitation program with no resolution to his cocaine addiction. But now he had a heroin addiction.

Rich Roll (74:17)

Right.

Matthew Walker (74:17)

And the story goes that he would, you know, have his shirts, his white shirts sent away to get laundered in places like Paris, you know, France. And they would come back both white and starchy, but there would also be other, you know, white related compounds in there. So. And we've never let go of that, you know, arcane and I think inane practice. And it's not medical residents who are at fault here, you know, speak to any of them, and none of them will tell you that that's what I want to be doing.

Rich Roll (74:49)

Yeah.

Matthew Walker (74:49)

You know, and I've had Conversations with a dear friend called Peter Attia who went through the medical practice is wonderful medical doctor and he describes some shocking history with a lack of sleep. And the statistics are just damning. Firstly, what we know is that medical residents who have performed a 30 hour shift will make 460% more diagnostic errors in the intensive care unit. Secondly, we know that if you're going to have elective surgery, let's say, and your surgeon has slept less than six hours in the previous 24, they're 170% more likely to cause a major surgical error such as rupturing a blood vessel or damaging or puncturing an organ. Then the irony is that a medical resident who's worked a 30 hour shift, when they get back in their car to drive home at the end of their shift, they're 168% more likely to get into a car crash. Now returning to the accident and emergency room from which they probably came. But now as a patient rather than a doctor, and you know, I've tried with many other people to lobby the medical institute or institution and try to understand why is this the case. And I think some of it has to do with the old boys network, that it's almost like a hazing that, you know, we went through it. So you have to, you know, you know, man up, suit up, boot up, woman up, you know, you, you need to get through this. This is a rites of passage. And again it comes back to that idea that thinking that you can fight mother Nature and evolution is just thick headed. And that's what this demonstrates.

Rich Roll (76:33)

I get the idea that you have to develop a level of rigor and emotional resiliency to handle that kind of job. And there is something to be said for, you know, putting people in challenging situations to see how they function under high stress. But the sleep deprivation aspect of it is just ridiculous.

Matthew Walker (76:53)

You know, if, if when you go through medical school, you know, you take an oath, which is to do no harm, and then you're placed under conditions of insufficient sleep that statistically will guarantee that you will do more harm than if you were sleeping or working, let's say just a 16 hour shift. I think some of the pushback that you receive or I've received is look, my mind's made up, don't confuse me with the data, right? And you think, okay, you're the doc, you're the scientists, what can I do?

Rich Roll (77:23)

You're the doctors.

Matthew Walker (77:23)

You know, isn't this self evident? And one of the arguments though I think that has some legitimacy is that of continuity of care, that if you are flip flopping back and forth between a resident every six hours, the continuity of the patient care can decrease. But then I thought about that argument for a long time and then I looked at a number of medical systems throughout the world and I asked how long does it take to train their residents and how good is their medical care? And what I found is that there are places like New Zealand, France, Switzerland, they all have their residents working no more than 16 hours. And their quality of healthcare actually ranks far better in the worldwide statistics than the United States. So you can't tell me that you can't train an individual within five years or less at a reasonable amount of sleep and not maintain a high quality of medical practice.

Rich Roll (78:22)

Right. Well, part of the problem tracks back to the fact that there's no education on this in medical school. Right. So these doctors who then become hospital administrators have the proper background to make a better decision about this.

Matthew Walker (78:37)

That's exactly right. So I also, you know, myself and some other researchers, you look at the medical curriculum throughout many of these world first world nations and what you discover is that the average medical resident will receive somewhere between an hour and a half to two hours of education on sleep relative to their entire medical program. Now that strikes me because that's one third of their patients lives and that 1/3 of their life spent asleep makes a profound difference to their 2/3 of waking health life. Why aren't we investing more in the education of sleep for our medical residents?

Rich Roll (79:21)

Well, why aren't we? Have you seen since the book came out and you've been, you know, speaking regularly on this, have you seen changes, positive movement in this regard?

Matthew Walker (79:34)

A little, but not, not too much.

Rich Roll (79:36)

Yeah.

Matthew Walker (79:36)

Unfortunately, I think there are some medical programs around this country, at least, that are doing better than others. There's a quite a variability. So some are prioritizing it and understanding its importance, but overall, no, I think that that same sort of, some of that hubris is still present. What do we do to change that? Well, you know, I tried early on speaking about this from the statistics of the patients, from a point of view of compassion and empathy for our young residents. And that sort of just falls on deaf ears. What I realized is that you have to speak in a currency with which, you know, medical institutions and administrators will listen to, which is dollars and cents. And when you start to rack up the numbers regarding malpractice suits caused by.

Rich Roll (80:27)

Insufficient sleep and they start paying attention.

Matthew Walker (80:28)

They start paying attention. Yeah. So I was just stupid. I thought about Appealing in the wrong language.

Rich Roll (80:36)

You gotta follow the money.

Matthew Walker (80:37)

Yeah, I know. Yeah.

Rich Roll (80:39)

But this Halstead reminds me of that TV show, the Nick. Did you watch this show?

Matthew Walker (80:46)

No, I didn't.

Rich Roll (80:47)

Steven Soderbergh did a limited series several years ago. I think it was for Showtime. I can't remember. But it's about this surgeon played by Clive Owen at the turn of the century. It's literally 1900. And he is an opium addict. And then he gets introduced to cocaine and heroin. But he's. He's this talented surgeon and he goes into the theater and you see the crazy surgeries that they were doing at the time. It's quite an interesting document. I think you would really like it. But I couldn't help but think, I wonder if this character who's modeled after.

Matthew Walker (81:21)

I suspect so I suspect if, you know, drug abuse, cocaine and such was involved. And he was this extraordinary power and force that sort of birthed into being, you know, this. This new way of medical practice. I, well, imagine it was based on.

Rich Roll (81:33)

Right, right, right. Well, the relationship between substance and substance abuse and addiction and sleep deprivation is another way in on this. You know, in this terrain. I mean, when you have all these doctors who are being compelled to stay up so late, they're going to find exogenous ways of, you know, enhancing their ability to do their jobs. And the treatment center that I went to many years ago was known for having lots of doctors and doctors and pilots, like the two people that you completely, you know, sort of divest yourself of any of all control over to. Right. And I just remember being struck at how many surgeons and pilots were in this treatment center. Right. Like there was a brain surgeon who was a morphine addict, and there was all kinds of pilots that were addicted to Vicodin. There were anesthesiologists that were fentanyl addicts. They would steal it when they would not use the entire vial. And they were using them primarily so that they could function in their job capacity.

Matthew Walker (82:35)

That's right. That's how it starts to sort of try to come back from the disruption. But what we know is that the risk or the probability of someone abusing drugs of abuse in the medical profession is significantly higher than the general population. To me, more striking. Well, an equally striking and equally worrisome statistic recently is that the rates of suicide are far higher in young residents. And what we've discovered over the past maybe 10 years, and we've been doing a lot of this work too, is the intimate relationship between sleep and your mental health. And what we know is that when you are not getting sufficient sleep, your suicidal thoughts increase, suicidal planning increases, suicide attempts increase, and tragically, suicide completion also increases as well. And more generally, what we've discovered, and I've been doing this for about 20 years now, we have not been able to discover a single psychiatric condition in which sleep is normal. And so I think sleep is a profound story to tell in our understanding, our treatment, maybe even our prevention of grave mental illness.

Rich Roll (83:55)

Well, certainly in saying that it should be the first stop on the kind of treatment protocol. Right. Like how is your sleep? Let's deal with that first before we look at pharmaceutical interventions.

Matthew Walker (84:05)

Yeah, it's a stabilizing force. And we know it's a stabilizing force both in terms of your psychology, as we mentioned, impulsivity, but also just from a basic reward, brain sensitivity, that your addiction potential from a brain perspective is higher with insufficient sleep. Same individual, two different sleep conditions, two different addictive profiles.

Rich Roll (84:30)

Right. Wow. I have to reassess my whole life now.

Matthew Walker (84:32)

Oh, I'm so sorry.

Rich Roll (84:34)

No, it's fine. No, it's good. I want to talk about sleep in adolescents and in teens because I think the work that you're doing here and the issues that you're trying to raise awareness around are super important. The implications of chronic sleep deprivation in young people, the relationship to early school hours, and how this plays out in terms of academic potential and the mental health implications that you just mentioned.

Matthew Walker (85:01)

Yeah. So there's been a remarkable amount of work looking at this issue of early school start times, this incessant model of marching back the school clock hours, and the summary of the evidence, really, I think it goes the following. Firstly, we see that academic. When you shift schools to a later school start time, so when you do a causal intervention, what happens? First, the academic grades increase, truancy rates decrease, psychological and psychiatric referrals also decrease. But what we also discovered is that the life expectancy of those students increased. And you may think, well, hang on a second, how does that work? Well, the leading cause of death in late stage adolescent teens is actually not suicide. It's road traffic accidents. And here sleep matters enormously. And there was one good example. I think it came from Teton county in Wyoming. They shifted their school start times from around 7:30 in the morning to just before 9:00 clock in the morning. The only thing more remarkable than the extra hour of sleep that those kids reported getting was the drop in road traffic accidents. That following year. After the time switch, there was a 70%, 70 reduction in car crashes in students 16 to 18.

Rich Roll (86:27)

Statistically unbelievable.

Matthew Walker (86:28)

It blows my mind. Now, you know, statistically you can give a relevance to that. Think of the advent of ABS systems in cars, anti lock brake systems that stop your wheels from locking up under hard braking. That dropped accident rates by around 20 to 25% and it was deemed a revolution. Yet here is a simple biological factor. Giving our kids the sleep that they need that will drop accident rates by up to 70%. So if our goal as educators truly is to educate and not risk lives in the process, then we are failing our children in a most spectacular manner with this incessant model of early school start times. You know, when sleep is abundant, minds flourish. When it's not, they don't.

Rich Roll (87:14)

Right. There's so much education, I think, that needs to be done in this area. As a parent of two teens, I've got four kids, two older boys. Any parent knows how difficult it is to wake up a young adolescent in the morning and the frustration that comes with that. But what I've come to better understand by dint of your work is how crucial sleep is for that developing brain. And during COVID we have one child, our younger child, who's being homeschooled right now. We've let her sleep in as long as she wants and we don't start her first class until noon. And so she's getting a ton of sleep. But if you even tried to wake her up at 9 o' clock, I mean, forget it, you're going to spend the next hour and a half trying to get this kid up. So clearly there's a reason why that state of sleep is so deep. Right. Like that. It is crucial in this developing, you know, in this developing mind.

Matthew Walker (88:15)

Yeah. And you know, we often have that classic idea of, you know, a parent at the weekend pulling the sheets off, you know, the teenager ripping open the toilet, the trauma, you know, you're wasting the day. But firstly, what we know is that it's not their fault. Because during that adolescent transition, there is a biological shift in their 24 hour rhythm that they now want to go to bed later and wake up later. So asking a teenager to wake up at 7 o' clock in the morning and operate and conduct themselves with good grace and be able to learn effectively is like an adult, you know, to wake up at 3:30 or 4 in the morning and be the best version of yourself. You know, if, if I was to wake up at, you know, 3 o' clock in the morning and come through to the kitchen and, or we were both awake. I'd have to say to my partner, you know, I would say to look darling, she. And she would say like, why are you so moody? I'm just not the best version of myself because I've woken up too early. And she will definitely tell you that. But I think it's the same misgiving because we don't understand how sleep works with our teenagers. And so putting them in the school at that time, seven or eight in the morning essentially is educating them amnesic. At that stage, they are leaky sieves. And what will happen go in, will just come out the other side. So that's the first thing that's happening. It's not their fault, it's just their biology. And then second, at the weekend, they're trying to sleep off a debt that we've lumbered them with during the week because of these early school start times. And if you ask parents, if you sort of question parents of teenagers, what proportion of parents think that their teen is getting sufficient sleep? And more than 70% of them say, I think my teen is doing fine. I think they're getting the sleep that they need. When in reality less than 15% of those teens are actually getting the sleep that they need. So there is a parent to child mismatch in sleep understanding. And as a consequence there is a parent to child transmission of sleep neglect. Parents don't see it, they don't understand it. And so, you know, in 15 or, you know, 10 or 20 years time, that teenager, lo and behold, seems to have amnesia. And they, with their own kids will do the same thing. They'll pull the sheets off and say, you're wasting the day. Because it was taught to them by their parents that sleep and getting the right timing of sleep and the right amount of sleep is something shameful.

Rich Roll (90:52)

So for that young person, do they need more hours?

Matthew Walker (90:57)

They do.

Rich Roll (90:58)

So the eight hour rule doesn't really apply.

Matthew Walker (91:01)

No, that's for adults. And in fact, the brain doesn't stop developing until it's about 25 years old. And sleep plays a critical role in what we call brain plasticity, which is modeling the brain. It plays a role early in life, in the first couple of years, sleep seems to actually help wire up the brain. So it's almost like sleep at that time of life comes in to a new neighborhood and like an Internet service provider, it wires all of those homes with high speed fiber optic cables. But then later in life, that's when during the teenage years, we've actually realized which homes are using the high bandwidth and which homes aren't really sort of drawing on that sort of, you know, that broadband speed. And so then the role of the brain, it goes from expanding, creating lots of connections, which is called neurogenesis, to then actually synaptic pruning, which is where we now have to make the brain efficient for adulthood. We sculpt away the unnecessary and we keep the necessary. And sleep performs that role too in later teenage years. And as a consequence, if you are chronically under sleeping, a teenager, you're effectively stunting brain development. And no one would wish that for their child.

Rich Roll (92:29)

Right. So you impede neurogenesis. So there's fewer pathways to choose from. And then as you age, then you're selecting. You're basically, you have less to choose from. Right. So you're just limiting the capacity, the brain's capacity to do its job well.

Matthew Walker (92:45)

So early in life, in the first five or so years, you want to sort of, you know, it's almost spray and pray attitude, a little bit like investing. You just gift all regions of the brain lots of connections. And then you let experience and time teach the brain. Which highways and sort of tributaries and avenues and lanes would you like to keep and which should be removed? So now, as you shift later in life, it's all about efficiency. Let's get this brain efficient. Because right now, when you've got this too much, too much connectivity, it's good to sort of as a general blueprint to lay down, but then let life tell you which of those sort of, you know, networks you should enhance and which you should actually remove. And it's later in life that we're removing those. And as I said, it's not until we're about 25 that the brain has finished all of that maturation. And that's why the recommendation is seven to nine hours in adults. And I would argue in adults, once they're past 25 years old, before that, you need much more sleep.

Rich Roll (93:52)

So what would be the ideal amount of sleep for the adolescent or young teen?

Matthew Walker (93:56)

Yeah, it's usually somewhere between eight to 10 hours and going up to maybe 11 hours, depending on that teen. And if people want to find out, there's a great informational sheet they can just go to the National Sleep foundation, it's the Nationalsleepfoundation.org and you can look at the current guidelines that we and other scientists have sort of tried to gather all of the information and say, look, where should we position these windows of sleep duration based on different age ranges? So it's a Great resource if people are thinking about that for their kids and for themselves as well.

Rich Roll (94:31)

So if you could, if you could bend the year of the, the Secretary of Education, I mean, what, what would be your recommendation in terms of school start time?

Matthew Walker (94:39)

Like 9:00am I think for teenagers, I would say 10:00am10? Yeah, 10 at the minimum. And what's interesting is that the younger kids, they can actually wake up earlier because they haven't gone through that adolescent transition. So, you know, they probably could be going to school and learning effectively at let's say 9:00am or even 8:30am but in those studies, they carefully ask the question, we can't set different times for different age brackets. You know, it's just not practical. And I understand why there is resistance in the school system. You can say, why are we starting that early? Some of it has to do a little bit with the bus unions, the bus networks that try to get kids to school. And I get that. I get, you know, it's not an easy problem to solve. But I also realized that we've put people on the moon and I think we can solve this.

Rich Roll (95:31)

Tougher problems to solve.

Matthew Walker (95:33)

And so I'm not trivializing it. It's a big problem and I don't have all of the answers. I'm just a scientist.

Rich Roll (95:38)

Well, there's the kind of mechanistic logistical aspect of solving that problem, but there's also the mental hurdle which comes with education. Right. Like getting somebody's head wrapped around the idea of why a 10am school start is in the best interest of the child is a hurdle.

Matthew Walker (95:55)

Right. And you know, for most parents, that's, that's their genetic legacy.

Rich Roll (96:00)

That's what you, you know, they're like, I gotta get to work too. Like, what am I supposed to, you know, so.

Matthew Walker (96:04)

Right. And that's the hard part. So what they did is they looked at, say, okay, let's say that we started school at 10 o' clock. That's only going to help the teenagers. But would it hurt the kids who are younger? Because that would then say, well, we can't do this one time fits all phenomenon. And what they found is that it didn't hurt the younger kids. They were learning just as effectively, but in the teenagers, they were learning far more effectively. In fact, if you look across the day and you ask, where are those school start times really hurting the teenagers? It's in the first half of the day because they're mostly asleep. And you ask any high school teacher, you know, what does my class look like first thing in the Morning versus in the afternoon. They're usually very different. As an audience.

Rich Roll (96:52)

What about dealing with things like SSRIs and treating ADHD with Adderall and Ritalin and the over medication of our young people and the implication on sleep and brain development?

Matthew Walker (97:06)

Yeah, I wrote a little bit about this in the book. It is unfortunate that that if you look at adhd, the current recommended treatment are things like Adderall and Ritalin and they are some versions of something that looks very much like amphetamine. And I'm not dismissing the idea that ADHD exists. I'm not one of those people. It clearly does. I also am not anti medication by any means. But what I would say is that unfortunately those medications are very strong wake promoting medications. I mean, if you ask an amphetamine addict, you know, if they need sleep when they're using amphetamine, they will laugh at you, right? They'll say, are you kidding me? I can go straight without sleep. And so maybe we need to think differently about at least the timing of that medication. You know, do we want to be medication kids in the morning or in the evening? Because if those things are wake promoting, we know that kids with ADHD have non normal sleep. They actually have disrupted sleep. And we're also starting to find that those medications themselves are sleep disruptors. And so one wonders what would be the efficacy, the benefit of those medications, which there are, but just timed correctly and you were at least able to try and protect sleep. Or what if we could just come up with better medications that aren't so destructive to sleep? I think that to me would be a better approach.

Rich Roll (98:40)

Is there research on antidepressant medication like the SSRIs and the implications for sleep?

Matthew Walker (98:46)

There are, yeah. So sleep is usually not normative when you're taking antidepressants. Now that's a general statement and it's too general. In fact, it really depends on which type of antidepressant because different antidepressants will shift different neurochemical systems in the brain. So SSRIs stands for selective serotonin reuptake inhibitor. And serotonin is a key neurochemical in the regulation of sleep. We have found historically that people taking antidepressants will typically have a reduction in REM sleep. It really seems to hit hard on REM sleep. And as we we may come on to discuss sleep and particularly REM sleep provides a form of emotional first aid. REM sleep is what I've described as overnight therapy. And there's nothing that I've seen That, you know, sort of is that much further from its effect size based on the evidence. And so one wonders whether or not we can look to alternative medications that again, have at least some conceptual sensitivity to the things that regulate sleep and try to stay away from disrupting sleep. You know, if sleep offers some form of assistance to depression. And we know that insufficient sleep predicts depression, we know that people who are depressed don't sleep very well. They have abnormal sleep patterns. So if sleep is a part of that disorder and disordered sleep is a part of depression, then shouldn't we think about the medications that they take that are also sleep disruptive and maybe think about finding ways where we time again the onset of the medication? I don't know how many doctors describe to their patients not just take two of these, but when, you know, seven o' clock in the morning could be very different than 7 o' clock in the evening. In fact, that's true of many medications in terms of their sleep disruptive capacity.

Rich Roll (100:48)

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Matthew Walker (106:22)

It doesn't. So this sort of idea of what's called highly polyphasic sleep, some people will describe it as the Uberman sort of schedule. Some people have said DaVinci is part.

Rich Roll (106:31)

Of this like self optimization. Right.

Matthew Walker (106:33)

Biohacking.

Rich Roll (106:35)

It doesn't work, right? Not a good.

Matthew Walker (106:37)

No, it really doesn't. And you know, there is, there is nothing in our biology that would suggest that's how we should be sleeping. And in fact, it's quite the opposite. In fact, there's a lot in our biology screaming, you should not be sleeping like that. You're not designed to be highly polyphasic in your sleep, meaning multiple bouts of sleep. You know, the only time that we do that is when we're infants, you know, and it's sort of, I think Billy Crystal, who's a long time insomniac, he's got this joke and he says, you know, I sleep like a baby, I'm awake every two hours, you know, and that seems to be, be this highly polyphasic mentality too. So that doesn't seem to be the case. That doesn't seem to be how we should sleep. And I would strongly advise people not to do that. Should we be sleeping though, differently than the way that we are in modernity? And I actually think there is an argument for this because if you look at hunter gatherer tribes whose way of life hasn't changed for thousands of years, they don't sleep the way that we do. They don't sleep in what we call a monophasic pattern, which is trying to get one long single bout at night and then we're awake for 16 hours. They sleep biphasically. So typically, depending on what season, be it winter versus summer, they will sleep for anywhere between sort of six to seven hours at night and then they will have this siesta like behavior in the afternoon where they have a nap, getting this sort of fuller opportunity. So I think modernity, you could argue, has actually dislocated us from how our natural edict of sleep schedule. Is there any other evidence to support that? There actually is. Most people will know this somewhere between about 2 to 4pm every day. You will have a drop pre programmed and it's genetically hardwired drop in your alertness. It's sort of, you know, that you're around the boardroom table after lunch and all of a sudden you start to see these head bobs going on. You know, it's not people listening to good music. They're just giving way to what we call the postprandial dip in alertness.

Rich Roll (108:45)

And it is decoupled on some level from the food coma. Right. Like part of it is, oh, I ate a big lunch. But this is independent of that.

Matthew Walker (108:53)

You can prevent people from having lunch. And they still have, you know, and I put electrodes on their head, we can still measure this alertness drop. So it is independent of food.

Rich Roll (109:02)

Right. So siesta.

Matthew Walker (109:04)

So siesta, you know, and you can ask, well, if that is how we were designed to sleep, is there any evidence that something goes wrong when you change that natural behavior? And that actually happened as a natural. Well, an unfortunate natural experiment in Greece a couple of decades ago. They decided that they were going to do away with the siesta policy. So if you went to Greece, you know, in the 1980s and you walked around the towns, you would see on the shop windows it would say open from, you know, 10 to 2pm, close from 2 to 5pm and then open from 5 to 10pm because there was a standardized siesta practice, they decided to do away with that. And so Harvard researchers said, okay, we're going to see what happens. What are the consequences? And they focused on cardiovascular disease. So they tracked the sleep and the health, the cardiovascular health of well over 23,000 Greeks. And what they found is that across that five year period, there was a 37% increased likelihood of having a heart attack. In fact, it was worse in males. In males, there was a 60% increase in likelihood of having a heart attack. And what was happening, it seemed, if you looked at the data, is that they were still sleeping the same, maybe just six hours a night. And they were doing away with the nap during the day. And they weren't replacing that sleep time back into their night phase. They were staying true to what they'd been doing before. At night and they'd just been shortchanged of their sleep during the day. And that led to cardiovascular health consequences.

Rich Roll (110:46)

Wow. So if no siesta, you gotta make sure you get the eight hours. But if you're doing, if you're engaging in that hunter gatherer practice, you can go six and two or whatever and that seems to be fine.

Matthew Walker (111:00)

I would say that there's probably a couple of caveats with naps though. Naps are a double edged sword. If you are struggling with sleep at night, the recommendation is do not nap during the day. Because what you want to do is build up all of that healthy sleepiness. And it's a chemical called adenosine. It's sleep pressure essentially. And the longer that you've been awake, the more of that adenosine, the more of that sleep pressure builds up. And it's not a mechanical pressure in your brain, don't worry, it's a chemical pressure to sleep. And then after about 16 hours of being awake, there seems to be enough adenosine, enough sort of sleepiness to be weighing down on your shoulders that now you can fall asleep and then stay asleep. So if you're someone who has fragile sleep or insomnia, you shouldn't nap during the day because taking a nap during the day will actually just. It's almost like a pressure valve on a steam cooker. You just release some of that healthy sleep pressure that's been building up and now when it comes time to fall asleep or stay asleep at night, it's that much harder. So the advice would be if you don't have sleep problems and you can nap regularly, then I would say naps are just fine. But if you can't do it regularly, and especially if you suffer from sleep problems, try to stay away from naps. If you are going to Nap, nap before 2pm in the afternoon. Going later than that can be problematic for your sleep. It's a little bit like snacking before your main meal. It just takes the edge off your appetite. It's the same way with naps.

Rich Roll (112:33)

I'm sure you or somebody has studied what happens if you take exogenous adenosine. Right. Like, wouldn't that seem to be the way in to resolving this problem for people that have insomnia?

Matthew Walker (112:46)

Hard to get it across the blood brain barrier, which is a protective layer around the brain. And you know, there's some issues around toxicity as well. So yeah, that certainly would have been the idea. But what's lovely is that, you know, you can increase sort of sleep pressure In a number of non pharmacological ways. And exercise is a great demonstration of that. And I think, you know, we can speak about all of these different over the counter medications that people try to invest in and think that that's going to give them a good night of sleep. But there are probably two really simple things that you can do. Non medication that are, if you look at the data, are almost guaranteed to improve your sleep, which is some form of physical activity most days or at least several days a week. And the second is deal with your anxiety. Anxiety is the principal cause of insomnia. It's not the only cause, but it's our current working model of insomnia that people who have a high fight or flight activation of their nervous system, branch of the nervous system, they also have high levels of stress chemicals such as cortisol. And that seems to be very predictive of their insomnia. And if you can start to manage your anxiety, for example, meditation is a fantastic practice. And you know, before I was writing the book and I was sort of starting to research, I was a bit of a stupid, hard nosed scientist. You know, I just thought this meditation stuff was maybe a little bit woo woo and sort of, you know, come by our. And we all hold hands and, and I started to look at the data. The data was immensely powerful and very robust that people when they are suffering from insomnia, if you put them into a meditation, a mindful practice, you can actually drop the severity of the insomnia in a way that medications. Yeah. Such even prescription medications can't come close to.

Rich Roll (114:45)

Yeah, I mean, I just know. Well, first of all, if I don't exercise, forget about it. Like I'm gonna, I know I'm gonna struggle with sleep.

Matthew Walker (114:51)

Yeah, me too.

Rich Roll (114:51)

At night. And if and when I have difficulty falling asleep or I wake up in the middle of the night, I've become very attuned to what my mind is doing and it will generally default to some problem that I'm having or conflict that I'm trying to resolve. And I'll just loop some narrative and that produces a tremendous amount of anxiety which obviously prevents me from falling asleep. So I notice that. And then I course correct through either some kind of mindfulness practice to kind of create space and push that narrative aside or you know, overcome it with a different narrative. And sometimes I'll just think about a book that I'm reading or a movie that I saw and I'll just immerse myself in that narrative and that's like a distraction Exactly. Literally short circuits that other anxiety producing narrative and I fall asleep.

Matthew Walker (115:51)

You're so right. So I think in this modern day and age, sort of the MTV, fast food 247 society, we're constantly, constantly on sort of reception, particularly with now all of this digital technology, and rarely do we do reflection. And unfortunately, the one time when we do reflection is when our head hits the pillow. And that's the last time that you want to go into rumination. You know, you don't want the Rolodex of anxiety spinning up, which is what you were sort of, you know, describing, because that leads to something that we call catastrophization, that you start thinking, oh, what didn't I do today and what do I need to do more of tomorrow? And then I forgot this. And at that point, you know, good sleep is not going to be invited into the brain. By the way, counting sheep does not work. There was a scientific study done by a colleague of mine at UC Berkeley that demonstrated, in fact, if anything, it hurts your sleep.

Rich Roll (116:46)

And what if you're catastrophizing? It would probably be better to start counting sheep.

Matthew Walker (116:50)

It could be. But what you described was actually what she found far better was to engage in some kind of a mental aspect. And what they found was take yourself on a walk. Think about a walk that, you know, in the forest or in nature or down on the beach and just start to try to walk yourself through that or think about, you know, a book that you're reading or think about sort of a podcast and anything to get the mind off itself. So, for example, I'm. I feel embarrassed to say this, but I love racing cars. And so if I'm struggling with sleep, which I do too, I am not immune to bad nights of sleep and I have bad bouts of insomnia. So comforting to hear that I'm just as fragile. And so what I'll do is I'll put myself and I'll think about the track and I'll drive myself around the track. I know which gear I need to be in, where my braking zones are. And then the next thing I know is I'm waking up in the morning and I just drifted off because I've taken my mind.

Rich Roll (117:50)

No, it's great. It's sort of a different version of what I do. What kind of cars do you race?

Matthew Walker (117:54)

Oh, gosh, I've raced all sorts. BMWs, Porsches. But my real love and the car that I own is a little Mazda Miardo. When you're a professor, you can't really Go racing in half million dollar cars and I love it to pieces. It is a car unlike a Ferrari or a Porsche, when you're going 40 miles an hour it feels like you're doing 100, whereas in a Porsche when you're doing 100, it feels like 40 miles an hour. So I'm usually the slowest guy on track, but it brings me a lot of joy and satisfaction.

Rich Roll (118:30)

That's cool. Well, let's talk a little bit about best practices then. I feel like we're at that juncture and I want to do this by walking you through the extreme lengths that I've gone to.

Matthew Walker (118:42)

I know a little of your sleep history. So tent included.

Rich Roll (118:46)

Yeah, I sleep in a tent. That causes a lot of consternation and confusion from people that listen to this show. But I'll just provide a little background to that. Historically, I've had issues falling asleep. Part of it, and I'm interested in your take on this is I think my sense is that it germinates somewhat from being like an extreme ultra endurance athlete. I've gone through periods of my life where I've put my body through just unbelievable rigor. Like 25 hour training weeks where you're just so exhausted. Sleep is a non issue. Sleep is not a problem when you're pushing yourself that hard. But it's been many years since I've been kind of habiting that space and now. But I've acclimated, my physical body is acclimated to doing that. Right. So now if I go out for a one hour run or I go on a casual bike ride, it's not enough. Like I'm not getting enough of the fatigue to create the restful state that I aspire to be in. Like I really, I have to exercise more than the average person, which is challenging when you're a busy person. So there's that on top of that. My body's like a furnace. Like I literally burn hot. And my wife likes the bedroom a lot warmer than I do. And we would have this back and forth over many years where it's too cold for her. I'm on top of all the COVID She's underneath them shivering. It wasn't working. And as kind of a joke I went and we have a flat roof off of our bedroom and I went and I just pulled a twin mattress up there and slept there one night and had an unbelievable night of sleep. I thought this is fantastic. It's nice and cold out, the desert air even in the summer. And that I graduated from that into Getting a tent. And I've been sleeping in a tent ever since. I absolutely love it. The cold air, being under the stars and being under a bunch of blankets, including a gravity blanket, which I'd love your thoughts on, which I found to be really helpful. Speaking about the sympathetic nervous system and trying to calm myself down and eye mask and nature sounds and, you know, magnesium, like all kinds of stuff. And the idea being, of course, to create the optimal situation for the best opportunity for eight hours of sleep every night. And like yourself, I don't always, despite all of that sleep still eludes me many nights. But more often than not I'm getting more high quality sleep than I used to. But I'm interested in how this kind of measures up with what you found through your studies about best practices, specifically temperature, air quality, all these kinds of things.

Matthew Walker (121:34)

Yeah. And so I think there are probably maybe five tips for better sleep tonight if you can suggest that. Or trying to optimize your sleep and temperature. Regularity, Darkness, walk it out. And then alcohol and caffeine. And I'll save the last one because usually if you don't find me deeply unappealing right now, you will after that fifth one. Temperature is a fascinating one. We know that your brain and your body need to drop their core temperature by about 1 degree Celsius or about 2 to 3 degrees Fahrenheit for you to fall asleep and then stay asleep across the night. And that's the reason that you'll always find it easier, easier to fall asleep in a room that's too cold than too hot. Because too cold is taking you in the right thermal direction for good sleep. And that's why sleeping in a tent, you're, you know, now we understand we're in Southern California, but nevertheless, you know, it can get. It gets cooler at night than it is during the day.

Rich Roll (122:36)

Yeah. I wouldn't be doing this in Boston.

Matthew Walker (122:38)

Right. Yeah.

Rich Roll (122:39)

It's still, I mean, typically it's low 40s and it goes down into the high 30s. And I've never not slept in the tent because it was too cold. I know that in your research you found there is an inflection point at which point perhaps, you know, too cold is not so good.

Matthew Walker (122:54)

Yeah. Once you get into an extreme, it.

Rich Roll (122:56)

But I have to tell you, like, you know, when it's 38 degrees, I'm happy. Like, I sleep pretty dang well.

Matthew Walker (123:02)

Yeah.

Rich Roll (123:03)

And that, I mean, I got a lot of. I got a lot of blankets on. Yeah.

Matthew Walker (123:06)

And so it's sort of, you know, the local Temperature may not quite be that.

Rich Roll (123:09)

And here's the other thing. Thing. I always have my feet sticking out. I cannot have my feet under the covers.

Matthew Walker (123:15)

Yeah. Do you know why?

Rich Roll (123:17)

Yeah, I think I know. But going.

Matthew Walker (123:19)

Because it's your hands and your feet that are these incredible radiators of heat. Your hands and your feet are highly vascular. In other words, there is this crisscross of vessels very close to the surface, and it's very rich in its vascular nature, both your hands and your feet. And so at night, what the body wants to do is almost like a snake charmer, draw the heat out of the core of the body and evacuate it through the extremities. And the extremities in this case for us human beings, are hands and feet as well as head. And that's why you will sometimes see rebellious. You know, when you see kids and you kind of tuck them in all nicely and, you know, you look at your wife and you smile and it's all beautiful. And then you go back in two hours later, just before, you know, you go to bed, and these rebellious legs are dangling out, you know, sticking out. It's because you're trying to evacuate the heat. So you're wise in doing that because they are wonderful thermal discharges. So that's temperature, and we do need to drop that temperature. It's different for different people. But I think the recommendation would probably be about, you know, 65 degrees or so for most people. Now, that's obviously averaging across men and women. And it's different there, too, as you mentioned, which is around about, if I do my math correctly, it's probably around about 18, 18.3 degrees Celsius. So that's temperature. And that's why I think you definitely will start to sleep better than you at least would do otherwise on a constant temperature. Because, you know, there's another way that modernity has dislocated us from our natural edict of sleep, which is we set a thermostat of maybe 70 or 72 degrees throughout the day and the night. And that's not how we were sleeping. Now, if you go back to those hunter gatherers, by the way, for whom you are in some ways mimicking their sleeping existence, they don't go to bed, really on the basis of light, which is what we thought. They usually will go to bed about an hour and a half to two hours after sundown. And then when they wake up, and they don't have alarms, if you ask them about this idea of, you know, artificially terminating sleep with an Alarm. They're perplexed. Also, you know, rates of insomnia in the general first world population is somewhere between 10 to 15%. In those hunter gatherer tribes, it's less than 5%. So something's.

Rich Roll (125:46)

They're also moving all day long.

Matthew Walker (125:47)

They're moving all day long. And, you know, we can look at diet as well. But what is determining their sleep onset? And their sleep offset is not light, it's temperature. So when and if you ask people, if you just bring them into the laboratory and you say, you know, at what point do you feel sleepy at night? It's at the point where their core body temperature is on the steepest decline. Now, they don't know that, even though, unfortunately, we've placed a rectal probe inside of them, which is no fun for either the experimenter to insert or for the participant to receive. But they are on the awesome downslope of their thermal evacuation, and that's when they feel sleepy. And when those hunter gatherer tribes wish to wake up is before dawn, just before dawn, but it's as the temperature starts to rise back up. So it turns out that we actually need to warm up a little bit to get cold. We need to bring the blood to the surface of the skin. That's why cold, it must be in the bedroom. But you can wear socks if you want, or you can have a hot water bottle, but keep it cold because warming the feet or sticking them out of the mattress will help your body evacuate the heat and plummet your core body temperature. And it's the reason, by the way, that hot baths and showers work for good sleep as well.

Rich Roll (127:10)

Not, you think, in a counterintuitive way. Right. Like because you think you're warming up nice and toasty. Yeah. You're vasodilating.

Matthew Walker (127:17)

When you get out the bath, you've got rosy cheeks, all of the blood comes to the surface. And when you get out of the bath, your core body temperature is dropping precipitously. That's why you fall asleep. It's called the warm bath effect in sleep science and so reliable. And then when they're starting to wake up is when they're starting, starting to warm up. So we need to sort of warm up to get cold, to get to sleep. Then we need to stay cold to stay asleep, and then we need to warm up to wake up. If that's the sort of temperature transition. So that's temperature. The next is regularity. Go to bed at the same time and wake up at the same time, no matter whether it's the weekday or the weekend or even if you've had a bad night of sleep, don't change it, Resist the urge. My recommendation to people who've had a bad night of insomnia, they'll say, should I get to bed earlier, should I wake up later, do nothing, don't go to bed any earlier, don't try to wake up any later, keep to your schedule. And by the way, I'm giving these sort of, these tips or these rules. People don't respond to rules. People respond to reasons, not rules. And that's why I'm, if you don't mind, diplomat trying to explanation as to underlying it. But the reason that regularity is king is because it will anchor your sleep and it will improve the quantity and the quality of that sleep. Because deep within your brain there is a master 24 hour clock and it expects regularity and thrives best under conditions of regularity, including the regulation of your sleep wake schedule.

Rich Roll (128:53)

Sorry, I just want to interrupt with one thing which is on that subject of the internal clock, does it matter in the context of getting eight hours if you choose to go to bed at 9:00 or you go to bed at 11:00, if you're getting eight hours, is that going to impact the quality of your sleep? I know personally, I need to go to bed early.

Matthew Walker (129:17)

Yeah.

Rich Roll (129:17)

If I still get eight hours but I go to bed late, it's not the same thing.

Matthew Walker (129:21)

Yeah. And so we mentioned that, you know, overall, for the average adult, you know, you get most of your deep sleep in the first half of the night, most of your REM sleep in the second half of the night. But it's not quite that simple. And by the way, you know, some people will say to me, isn't the sleep that you get before midnight twice as valuable as that you get after midnight? You know, the stroke of midnight, you know, there's nothing about the sleep that you were getting at 11:59, you know, PM and the sleep that you're getting at 12:01am, that's a fallacy. But what you described is important and it's a nuance and it comes back to what we call chronotype. Are you a morning type, evening type or somewhere in between? And it's about a third split across the population. You don't get to decide. It's not. If you're a night owl, it's not your fault. It's gifted by way largely of your genetics. It was gifted to you at birth and it is hardwired. And we now, know the genes, at least six different genes determine whether you're a morning lark or an evening owl or sitting somewhere in between.

Rich Roll (130:25)

But it's interesting to know that that's a genetic disposition. You can't compel a night owl to be a morning person.

Matthew Walker (130:31)

No. People have done all sorts of incredible things and there is some degree of wiggle room you can do. I think there's about five or six different things, things that they tried, but all you can really do is drag a night owl back by maybe 30 minutes and that's really it. So what you're describing there in terms of the quality of your sleep is important because it's less about where any adult places their eight hours on the 24 hour clock face. It's more about where that individual adult is trying to sleep in harmony with their chronotype rather than against their chronotype. Now, unfortunately, modernity is, you know, is predisposed to a heavy bias and a discrimination towards morning types. You know, it's this type a culture that rise and grind. You get up in the morning and it's all about the early bird catches the worm. Well, I can also tell you that, you know, the second mouse gets the cheese, you know, so you need to be really mindful of your chronotype. Now you can figure out your chronotype if you want. You can just go online and you can what's the best? Probably search something called morningness Eveningness questionnaire and I can send you a link that we can even put in the show notes, the meq and it's a series of questions and you will determine what type you are trying to then sleep at the right timing, in accordance, in harmony rather than in desynchrony with your chronotype is when you will get the best quality of sleep. That's why you say if I go to bed at midnight and I sleep in till eight sometimes I kind of have a sleep hangover. I just feel miserable. But if I get to bed at whatever time you normally do earlier in the evening and wake up earlier, that's my sweet spot.

Rich Roll (132:19)

Most people probably know what their type is. They do, right?

Matthew Walker (132:22)

Well, I think yes and no. Because, you know, in some ways even the middle ground folks will think that they are, you know, perhaps more evening type than they actually are because of technology. Now we've done a lot of work in the sleep field. We, the royal we, by the way, in this podcast, when I've said we did something, I mean that sort of, or when I say I did something I mean sleep science community, we did something. And when I say we did something, I mean they did something. But so we've done a lot of work looking at technology and the invasion of technology into our lives and into our evenings and into the bedroom. And certainly those blue light devices are damaging to the release of melatonin, which we'll come onto when we speak about darkness. But it's not really that which now seems to be carrying the vote of technology based sleep disruption. It's that these things are activating, they are designed to capture your attention and make you more alert. And in fact it's what ends up happening is that you have sleep procrastination where you're using these devices, you're working on your laptop and you think, I'm not sleepy, I don't feel tired. But if there were to be some electromagnetic pulse that wiped out all of technology, you know, what you would realize is that at 10:30 all the lights went out. You couldn't do anything within five or ten minutes. You think, wow, gosh, actually you know what, I really am sleepy. And technology will mask your sleepiness. That activating nature of technology hits the mute button on your sleepiness so you don't perceive it.

Rich Roll (134:06)

Right. In a multifaceted way. Right. There's the dopamine induction of social media scrolling, but there's also the light spectrum and all of that. Right. That's you know, impacting your body's ability to properly self regulate.

Matthew Walker (134:21)

Yep. Yeah. And so, you know, I often, if you really have to take your phone into your bedroom, I don't personally, but again, you know, that's just me. I would say the one rule I would offer to you is that if you're going to be using your phone in the bedroom, you have to be standing up, you know, and at that point, after about five or six minutes.

Rich Roll (134:40)

You'Re not doing anymore.

Matthew Walker (134:41)

You're like, you know what, I just want to, if you sit down on the bed, I'm sorry, phone goes away.

Rich Roll (134:45)

Here's what's depressing though. And you talk about this like what it went how, like how long before you need to go to bed should you shut the screen off? And it was like a number of hours, right. Like if you watch a movie and then go to bed, that movie should be concluded. Like, I don't know, what did you say, like two hours or something like that?

Matthew Walker (135:04)

Well, it really depends on sort of, you know, watching television or a movie. As long as it's not inside of the bedroom, we really shouldn't Be watching television inside of the bedroom because you want to associate your bed with simply the place of being asleep or for intimacy. That's really what we recommend the bed for. Don't be working on there, don't be eating on your bed, don't be watching television on your bed, consuming Netflix. And I think it's really about computers and, you know, iPads and cell phones or laptops, sorry, tablets. I think watching television outside of the bedroom is okay. One of the dangers, however, when I ask people, you know, if they say I'm having sleep problems, I'll say, you know, do you nap during the day? And they'll say, no, I never nap. Then I'll say, well, but when you're watching television on the couch in the evening, do you sometimes fall asleep watching television? They say, yeah, I do that all the time. That's an accidental nap. And it's the worst time to nap too, because again, it's right before your main meal of sleep. So I would say that if you're doing something that helps you wind down and just disengage from the day, disengage from those stressors. That's fine, be it reading a book, watching a mindless movie, but in the last hour before bed, stay away from anything that you know is cognitively and especially emotionally activating. Don't be checking emails, don't be sending texts, you know, don't be engaging in movies that are, you know, action horror movies that have you wired.

Rich Roll (136:32)

Right.

Matthew Walker (136:32)

Try to stay away from those things.

Rich Roll (136:33)

Right, yeah. So let's talk about caffeine and alcohol. Right? So disappointingly, caffeine has like an eight hour half life, right? So if you have a cup of coffee in the morning, you're still contending with it when you go to bed.

Matthew Walker (136:46)

It's tough. Yeah. So alcohol and caffeine. So everyone knows that caffeine is an alerting substance. It's in a class of drugs that we call the substance psychoactive stimulants. Interesting. It's one of the only psychoactive stimulants that we readily give to children without too much concern. So, you know, many people know that that's how caffeine works. But people may not realize that caffeine can have two additional damaging effects on your sleep. The first comes down to, as you said, the duration of action. That caffeine has for most people, a half life of what we call about five to six hours. In other words, after about five to six hours, 50% of that caffeine is still in your system, which Means that caffeine has a quarter life of between 10 to 12 hours. So if you have a cup of coffee, let's say 2:00pm, a quarter of that caffeine could still be circulating your brain at midnight. So it would be the equivalent of, you know, a 2pm cup of coffee is the equivalent of getting into bed. And just before you turn up the light, you swig a quarter of a cup of Starbucks and you hope for a good night of sleep. It's probably not going to happen. Yeah, there are differences from one individual to the next. It comes down to the specific enzyme that degrades caffeine. Some people have a genetic variant, what we call a polymorphism that has a faster metabolic rate for the degradation of caffeine. Other people have slow. That usually determines. I'm a sensitive person, I'm not sensitive. But even if you're one of those people, and some people say this to me, look, I can have an espresso with dinner and I fall asleep fine and I stay asleep, so no problem. That's not quite true because even if you fall asleep and stay asleep, caffeine can actually decrease the amount of deep non REM sleep that you get. Can decrease the quality of that deep sleep by up to 20%.

Rich Roll (138:37)

Wow.

Matthew Walker (138:38)

Now for me to drop your deep sleep quality, I would have to age you by a decade. Or you could do it with a cup of coffee in the evening each and every night. And the problem is that then those people, when they wake up the next morning, they don't remember struggling to fall asleep. They don't remember waking up frequently throughout the night. So they don't put two and two together. But now they feel unrefreshed and unrestored by their sleep because they weren't getting the deep sleep. And now they find themselves reaching for more caffeine, three cups of coffee in the morning, and then because they may not be able to get to sleep at night, then they're reaching for sleeping pills. So it's this sort of, you know, it's this stimulant in the morning, it's a sedative in the evening, and it's a very difficult cycle to break. So that's caffeine, alcohol. Alcohol is probably the most misunderstood sleep aid that there is out there. It's anything but a sleep aid. And, you know, you've mentioned how your sleep was so disrupted. Firstly, alcohol is in a class of drugs that we call the sedatives. And sedation is not sleep. But when we have a couple of drinks in the evening and we say, gosh, I just fell asleep like that. You're mistaking sedation for sleep. So if I were to show you your electrical patterns of brainwave activity with and without alcohol, they're not the same, it's not naturalistic brainwave activity. The second problem with alcohol is that it fragments your sleep so that you wake up many more times throughout the night. So not only is your sleep, you know, going to be poor quality as we'll come onto, it's also just not going to be consolidated. It's not that nice long duration of.

Rich Roll (140:17)

Uninterrupted sleep because as your body is processing the alcohol, the depressant aspect of that drug is wearing off and there's a sort of rubber banding stimulant reaction to it. Right. So you wake up at 2 or 3 in the morning.

Matthew Walker (140:32)

Yep. So it actually will start to, just as you mentioned there, it will trigger activation of the fight or flight branch. So you start to come back online in terms of that stress related branch of the nervous system. Also, stress related neurochemicals we know are starting to get increased as the alcohol is metabolized. And that's what causes the fragmentation of your sleep. The final problem with alcohol is, is that it's a very potent suppressor of your REM sleep, of your dream sleep, which we've mentioned before in terms of all of its benefits. And so, you know, I think that's the reason that alcohol should just be strongly advised against, you know, against the nightcap by medical practitioners. But I would just say two things. Firstly, with tongue in cheek, you know, you could look at that data and say, well then I should just go to the pub in the morning and that way the alcohol is out my system in the evening. And now I'm foul.

Rich Roll (141:24)

But yeah, the problem with me is if I go to the pub in the morning, I'm at the pub at night too.

Matthew Walker (141:28)

And so I would never say that as a healthcare professional, but what about.

Rich Roll (141:32)

Like just a glass? Like, hey, I'm having a glass of wine at dinner.

Matthew Walker (141:36)

Yeah. I would love to say that, you know, based on the data, that doesn't have an impact, but if you look at the data, even a glass can have a measurable impact. But look, the other thing I want to note is this, and I think it's something that I've learned in after the book was published and I'm embarrassed in the way I was acting before. I don't want to be puritanical here, Rich. You know, I don't. I Don't want to tell people how to live their lives. I'm just a scientist. All I want to try and do, and I may be too enthusiastic in doing this, is gift people with the science, science and the knowledge of sleep, and then they can make an empowered choice as to how they want to live their life if they're trying to optimize their sleep. So I do want to mention that I'm not finger wagging and I shouldn't be telling anyone how to Matt.

Rich Roll (142:24)

I don't think anyone's getting that impression. I think it's, it's like, look, this is what's going on. Like, make your own, you know, choose accordingly. Right. But just so everybody knows, like, let's be clear about what the science says in terms of how this impacts you.

Matthew Walker (142:37)

Yeah. But I think I've been sometimes overstepped.

Rich Roll (142:39)

The mark, so it's good you're such a gentle guy. But I also should say, like, I love how enthusiastic because you talk about this stuff a lot, but you're so enthusiastic, your whole body, like, lights up when you talk about this stuff.

Matthew Walker (142:53)

It's the most. I fell in love with, you know, I fell for sleep like a blind roof, you know, it was just the most amazing thing as I was starting to see study it. And it is a love affair that has lasted me 20 years. And I am still beguiled by this beautiful thing called sleep at night.

Rich Roll (143:11)

Yeah. There's so much more still to be learned. Right? Like, yeah, you know, I mean, it's.

Matthew Walker (143:17)

You know, I think it's remains one of the last great scientific mysteries. I would say, though, and the reason that you're able, you know, someone like me is able to write a book that's over 130,000 words is because, you know, we've learned more in the previous 50 years about sleep than we did in the previous 5,000. And even just 30 or 40 years ago, we used to ask the question, you know, what is sleep good for? And the crass answer was that, well, we sleep to cure sleepiness, which is the fatuous equivalent of saying we eat to cure hunger. That tells you nothing about the nutritional, physiological, metabolic benefits of food. Now, 30 or 40 years later, we've had to upend that question. And we've had to ask, is there any major organ system in your body or is there any operation of the mind that isn't wonderfully enhanced when we get sleep or demonstrably impaired when we don't get enough? And the answer seems to be no.

Rich Roll (144:17)

Right. I have to ask you this Every full moon I don't sleep and I don't know if it's psychosomatic or there's some kind of lunar gravitational pull occurring, but have you looked at this?

Matthew Walker (144:30)

We have.

Rich Roll (144:31)

Have you?

Matthew Walker (144:31)

Yeah.

Rich Roll (144:32)

Please do tell.

Matthew Walker (144:34)

There's some conflicting evidence. So some reports have found this effect, other reports have not. And it may be different for men and women. Even some of the reports are saying on average people sleep less with a full moon. So have you ever thought about the term? What the term means lunatic. And it occurred to me when I was doing that work based on the relationship between sleep and your emotional health, that you essentially, your emotional integrity falls apart when you're not getting sufficient sleep. You become emotionally unhinged. You become pendulum, like in your emotional irrationality. It occurred to me, I wonder if part of the derivative of that term, you know, we've got all these things, you know, the werewolf and people getting forever.

Rich Roll (145:21)

Right? Yeah, yeah. Like when the moon's out, people lose their minds.

Matthew Walker (145:25)

Right. And you know, I think some of that is due to, you know, different practices around the celebration of the moon phases, et cetera. But, you know, I think if you believe some of the reports, but again, some of the reports have failed to find this effect. Sleep duration decreases. Why would that be? There are some theories around that which actually I should finish up my tips and there's just two more of them. But this is nice because it brings us back to this with a full moon, obviously, as long as it's not a cloudy night, you get more luminance, right? And that light of that luminance can actually decrease the hormone of melatonin. And this comes back to what were, I think, the fourth out of the five tips, which is darkness. We are a dark deprived society in this modern era and we need darkness at night to trigger the release of this hormone called melatonin. And melatonin is often called sort of the vampire hormone, not because it makes you want to look longingly at people's necklines and, you know, bite in. It's because it comes out at night. It's the hormone of darkness. And melatonin helps the time, the healthy onset of sleep. And so the recommendation would be, in the last hour before bed, don't just stay away from those blue light emitting devices. Try dimming down half of the lights in your house. You would actually be surprised at how sleepy and soporific that change can be. And that's why I love the idea of sleeping in a tent, because all of a sudden you know you are removed from all of that, you know, polluting electric light even at night. Now, we should reverse engineer that trick during the day. In the first half of the day, it's critical to get some exposure to daylight. You can go outside, but it doesn't mean that you have to go outside just being next to a window. Try to get at least 40 minutes of direct sunlight each and every morning. And that will really help because that will then stamp the brakes on melatonin. It will shut it down and you will feel more alert. The more alert you feel, the more healthy sleepiness, the more of that adenosine, which is the sleep pressure chemical that you will build up, and then the better your sleep will be at night.

Rich Roll (147:42)

Right.

Matthew Walker (147:43)

So that's sort of darkness. And I think that's perhaps part of the explanation why the full moon can maybe disrupt our sleep. Because it's nowhere near like sunlight, but it's still a light invasion.

Rich Roll (147:54)

But I wear the eye mask and the whole thing. I think there's something more mysterious at play. I don't know, but maybe I'll try taking melatonin. I know that you've said taking melatonin as a matter of course is not a good idea. It's really for when you're traveling across time zones. But maybe I'll try it when the next full moon cycle comes.

Matthew Walker (148:15)

You can try it. I mean, melatonin, as I mentioned, it regulates the timing of your sleep, but it doesn't actually really help in the generation of sleep. If you look at people who are not jet lagged and who are under the age of 50, melatonin, in all of the placebo controlled studies that we found, doesn't really change the quantity or the quality of your sleep. Melatonin, you can think of it a little bit like the starting official at the hundred meter race. You know, melatonin is the thing that will gather all of the races to the start and then begin the great sleep race. But melatonin doesn't participate in the race itself. That's a whole different set of brain chemicals. But I would say two things regarding melatonin. First, if you think that it's working for you, then the placebo effect is the most reliable effect in all of pharmacology, with the exception of probably an adrenaline injection to your heart. So no harm, no foul there. The caveat that I would like to add to that secondarily is it's over the counter, at least here in the United States, which means it's not regulated by the FDA. And in a study that looked at over 20 different brands of melatonin, what they found is that based on what it said on the bottle, relative to what was actually in those melatonin pills, it was anywhere between 80% less, up to 460% more than what it said on the bottle. So it's a wild west. You don't really know what you're.

Rich Roll (149:46)

Is there a trusted brand?

Matthew Walker (149:49)

Well, I think, you know, firstly, I should also mention that melatonin is still largely a safe compound, you know, even in high doses. You know, it's, it's, it's concern from that aspect is perhaps lower, but because it's unregulated, one of the things I've been seeing right now are melatonin gummies for kids. And maybe we'll learn more about melatonin and it could help kids with sleep problems or sleep disorders. But if it's unregulated, you don't know what dose you're giving.

Rich Roll (150:19)

Wouldn't the concern also be, if you're taking it all the time, doesn't that signal your body to stop producing it?

Matthew Walker (150:25)

That's right. So that's the other major sort of issue, is that most people are taking too much melatonin. They're taking usually between 5mg up to 10mg. I would recommend, based on the science, somewhere between just 0.5 to 3 milligrams. Because if you're dosing any higher, your body has this beautiful network of feedback loops and it starts to think, well, my goodness, you know, I don't need to produce melatonin because I'm getting it every night in very high dose. I can just shut down my own melatonin production. So that's the danger. Just be a little bit mindful on.

Rich Roll (150:59)

The subject of light. You know, talking about the light on a full moon. I've come to develop a greater appreciation for the brain's capacity to process spectrums of light and how that relates to how we calibrate our internal clock. Like, I had neuroscientists. Andrew Huberman here, do you know?

Matthew Walker (151:20)

Oh, yes, from Stanford. Yes.

Rich Roll (151:21)

Right, right, right.

Matthew Walker (151:21)

Actually, we've never met. You guys gotta meet, but we know of each other and we should, at some point we should get together and mind meld because I think we'd have a lovely time together.

Rich Roll (151:30)

Yeah, yeah, he's doing some interesting work. But he talks a lot about how really the eye is, you know, is, is the brain, right. Like the optic nerve is part of the brain. And the sensitivity of the optic nerve to all these variations and in light spectrum. He talks about looking at, you know, at how looking at a sunset, you know, kind of helps calibrate all of that, all of these different things. And I was thinking about that the other day because I play this game when I wake up with myself, when I wake up in the morning, I open up my eyes, I don't have an alarm clock, and I try to guess exactly what time it is. And it's pretty amazing. Like, I'm generally, I don't always get it right, but I'm generally like within two minutes of the precise time. And I thought, is that because my eye knows the specific light spectrum of what time of day it is, or is it my internal clock? Like, what is that? But there is this deep knowing, I think, that we have, when we are more in nature where we're attuned to these rhythms.

Matthew Walker (152:32)

I think it's a combination of both. And by the way, his work is just fantastic. If, if people. I know you've had him on your show, just listen. He is just a brilliant scientist and he's so eloquent and beautiful.

Rich Roll (152:45)

He's a very effective communicator. He knows how to explain things in a way where people can really understand what he's talking about.

Matthew Walker (152:51)

Yeah, he's wonderful. But. So I think it's a combination of those two things. I think many of us, even if we've got blackout curtains and sort of we're wearing an eye mask, we will wake up. And I think we have some, some general sense, but maybe plus or minus an hour in terms of accuracy, that, okay, it's still probably the middle of the night or it kind of feels like late in the morning. And in part that's because you do have an internal 24 hour clock. But I also think that there's something that we've lost in terms of our light exposure that you have gained back, which is that it's not just that your internal climate clock, which may get you, you know, within one hour plus or minus it, it's not bad at doing that. But when you open up your eyes and you get additional exogenous information, which is from the outside world, rather than the endogenous clock time that your 24 hour clock is giving you, then you shift from plus or minus an hour of accuracy to maybe plus or minus five minutes, you know, and so when I retire, maybe I'll look at this because there's something very strange about sleep and time that is utterly paradoxical and What I mean by this is you can say, okay, I've got to wake up. Cause I'm going to, you know, I'm gonna fly out and meet Matt Walker in Berkeley. We're gonna grab coffee, and I've got to get this early morning flight from LAX. And you set your alarm for 5 o' clock in the morning and guaranteed you will wake up at 4:58.

Rich Roll (154:29)

100%.

Matthew Walker (154:30)

How is that possible? It happens too frequently for it to be just by chance. So somewhere your brain has this quartz, like, precision of clock counting. However, there is an absence of time, particularly in dreaming, because all of us have probably had that experience that our alarm goes off and we were in this strange dream, and then we hit the snooze button. And our snooze button is just two minutes. And we go back, and we go right back into the dream again. And then the snooze button goes off. And you think, now hang on a second. I was. That felt like almost an hour of an experience. So there is this temporal mismatch where when we go into the dream state, we can almost feel, fold and compress time like a concertina.

Rich Roll (155:21)

It's like Inception.

Matthew Walker (155:23)

Yeah. And I think it's no big surprise that Nolan picked up on that. You know, with the help of maybe some, you know, sleep specialists offering that advice. We know that you get this, you know, this dilation. I've called it sort of dream dilation or dream time dilation, where time.

Rich Roll (155:39)

So what do you. Right, like, so what do you. What do you make of that? Like, what would be the evolutionary advantage of that?

Matthew Walker (155:46)

Well, it may be that there is no necessarily evolutionary advantage, but there may be a brain mechanism that explains it, because what we know is that memories are replayed during both deep sleep and REM sleep. Now, when we are in deep sleep, memories are actually sped up. The brain will actually be replaying those memories anywhere between five to 20 times faster. But when we go into dream sleep, the replay is actually much slower. And so that may be why, if you want to speak about. That's usually the one question I look forward to. Least when I give talks, someone put their hand up and say, is inception possible? And my heart just sinks. I start seeing a spinning top and the music that comes by. But I think that that's why Nolan had that beautiful idea that when you descend down into these different levels of sleep, you know, a minute of time in the real world could be, you know, five minutes of time in the dream world. And then if he gets you to deeper Dream states, you know, then, you know, a minute of time in the real world is two hours or two days or 50 years.

Rich Roll (156:58)

Well, with the premise being I'm going to anchor this memory or this concept or this idea in this human's brain. And the way to do that, how do you do that in an effective way where it's going to stay right. And when you think about this in the context of morphing time constructs, if you have a dream state in which memories are accelerated, that's certainly going to aid in the development of skill acquisition. You're repeating a memory or a behavior, or just imagine, you know, you're in jiu jitsu and you learned a new maneuver or whatever and you're replaying that in your mind. Of course that's going to anchor that. And then the slowing down is almost like a visualization. Well, but both of those things would work in tandem to really, you know, sort of calcify neural pathways around like a new concept.

Matthew Walker (157:48)

You need to be a scientist. Rich, would you direct my sleep sense of.

Rich Roll (157:53)

My mom would be very happy back to medical school.

Matthew Walker (157:56)

No, you're too precious in what you do otherwise. But you're absolutely right that I think what we know is that deep sleep, well, one of its functions is that it will hit the save button on your memories so that you don't forget. So deep sleep will future proof that information within the brain. And in part, it's just as you said, it's deep sleep that's basically scoring the memory trace, almost etching it into to the glass of the brain. But then dream sleep comes along and what we've realized is that dream sleep does something very different for memories. Sleep is much more intelligent than we ever gave it credit when it comes to information processing. Sleep not only strengthens individual memories, it will intelligently stitch and associate those new memories together. And it seems to be during sleep, particularly during dream sleep, when we perform, it's almost like informational alchemy, or it's like group therapy for memories. Maybe that's a better analogy. You know that sleep gathers in all of this information that you've been learning during the day and everyone gets a name badge. But sleep forces you to go and speak to the people not at the front of the room that you think, I've got the most obvious connection with. It forces you to speak to to the people at the back of the room that you think you've got no connection with at all. Now it turns out that you do, and it's a non obvious connection, but it's a potentially powerful one nonetheless, because when you start to fuse things together that shouldn't normally go together but offer marked advances in evolutionary fitness, it sounds like the biological basis of creativity. And that's where we see dream sleep providing a benefit. You wake up the next day with a revised mind wide web of associations, and you are capable of divining solutions to previously impenetrable problems. It's the reason that you've never been told to stay awake on a problem.

Rich Roll (159:53)

Right. Sleep on a problem. But it has a very strange and elusive relationship with memory. Like memory doesn't seem to really be required for this. Right. Like sometimes you, the recollection, you remember something, some of this stuff, and then it fades. But nonetheless the brain is doing its job in that state and you're able to come up with a creative solution or solve a problem that mystified you the night before.

Matthew Walker (160:17)

Yeah, and I have another. It's probably second only to the idiocy of my idea that we never evolved sleep that we have. You know, it was from sleep that wakefulness emerged that we started at the top of the podcast. The other stupid theory is that in fact we remember all of our dreams. You know, most of us when we wake up, we, if we can remember a dream, it's usually very difficult and different people have different dream recall strengths. And the harder that we try, you know, the unlike, the more unlikely it is. But I think that that's not a problem of memory imprinting. I think that's a difference in memory science that we call accessibility versus availability. I think when we wake up in the morning, we lose the IP address to the memory, so we can't find it. So its availability is still there, but its accessibility is prevented. And the reason I think this is a tenable theory, and I've got some ideas as how to test it, is because you can wake up in the morning think, oh, I was having this incredible dream and, and, and you just can't bring it back to mind and you think, okay, it's just gone. And then two or three days later you're walking down the street and you see a sign, or you're in the shower and you see the shampoo bottle and all of a sudden there's a cue that triggers the unleashing of that dream memory and it all comes flooding back. In other words, that memory was there all along. You just didn't have accessibility ability to a still yet available and present memory. Now, if that's true, what it could mean is that we store all of our dreams. And the reason I find that sort of hand waving wacky and fun philosophically to think about is we know that memory operates largely in a non conscious manner. You know, you can, for example, if you're walking up a set of stairs and you, you know, you've got your pad of paper and you've left a drink on the stairs, you know, you sort of, you're reaching down to pick it up. That's an immensely complex challenge. You had to sort of compute the physics of where your hand was. You had to know what the weight of that cup was. This is all based on memory and it operates way below the radar of consciousness. Most memories do. If that's true, that our behavior is certainly influenced nonconsciously by our memories. It's what we call implicit memory and we remember many of our dreams. Then all of a sudden it becomes interesting to ask how much does our waking life reflect or is shaped by.

Rich Roll (163:00)

Our stored dreams in an unconscious way?

Matthew Walker (163:03)

In an unconscious way. Now this is getting very Freudian and I have to say I'm not a big advocate of Freud. I think he, you know, he did a remarkable service to the science of sleep. He brought dreams into the world of the mind. Before it was, you know, in the Greeks it was coming from gods, you know, hypnos, somnus, you know, Morpheus. And then Chinese cultures had an idea that dreams came from the soul. But it was Freud who actually placed dreaming squarely within the mind. In other words, Freud made dream science a domain of brain science, of neuroscience. Now after that, it all kind of went south, you know, and I often joke that I think Freud was 50% right and 100% wrong. And so. And it's not a testament when it.

Rich Roll (163:45)

Got into the interpretation aspect.

Matthew Walker (163:47)

Exactly. And that's just. And we've demonstrated that. It's why it's no longer embraced by the scientific community as a scientific hypothesis, because it's untestable, it has no solid predictions. And I think it's good to keep in mind that, you know, there are some reports that at the time, Freud was doing enough cocaine to kill a small horse when he was coming up with some of that too. So maybe you want to talk to cocaine. Yeah, I know. Well, what is it about me? I can't see to get away from it. So I think I have this enamored theory about dreaming and it's just not very fundable. So it's hard to get the funds.

Rich Roll (164:20)

I mean, I think it's the ultimate unknown terrain and Just unbelievably fascinating, the idea that our brain is so complex and it's performing this mystical dance and computation while we sleep. And the extent to which we barely begin to understand what that's all about, I think is just super interesting.

Matthew Walker (164:46)

I mean, and you mentioned this, you know, very early on in our taping about dreams. It is another very strange state, you know, because last night, you and I both became flagrantly psychotic. Right? And we did that multiple times throughout the night. Now, before you dismiss my kind of, you know, diagnosis of our nighttime psychosis, I'll give you five good reasons. Firstly, when we went into dream sleep, we started to see things which were not there, so we're hallucinating. Second, we believe things that couldn't possibly be true, so we're delusional. Third, we get confused about time, place and person, so we're suffering from disorientation. Fourth, we have wildly fluctuating emotions, something that psychiatrists call being affectively labile. And then, how wonderful. You and I woke up this morning and we forgot most, if not all, of that dream exercise. And we were paralyzed from amnesia.

Rich Roll (165:40)

We were paralyzed throughout.

Matthew Walker (165:41)

Yeah. Many people don't realize this, that when you go into dream sleep, your brain paralyzes your body so the mind can dream safely, so you don't act out your dreams. And there is the parts of the brain that actually control the different stages of sleep, in part, are deep down within the brainstem. Now, when the brain is ratcheting up its upstairs activation of the brain for REM sleep, for dreaming, it sends another signal down along the spinal cord and it paralyzes what are called the alpha motor neurons in your spinal cord. These control all of your voluntary skeletal muscles. So when you deliberately want to move your hand, move your foot, sort of change your mouth, speak, etc. So you are locked in physical incarceration during REM sleep. You are imprisoned within your own body.

Rich Roll (166:33)

So when you have that, or I should say when I've had these experiences where I'm being chased or something's happening and I feel like I'm stuck in molasses or I want to scream. And I'm like, my wife will. Julie will. Like, the next morning, she'll be like, you are making the weirdest noises. And I'll have some memory that will trigger a memory like, oh, I was being pursued and I was trying to get away and I couldn't. And I was screaming out for help, but I couldn't even make a noise.

Matthew Walker (167:02)

That's exactly why, you see Too much of good science.

Rich Roll (167:05)

So is sleepwalking then a malfunction and that paralytic system? Like what's happening when you're sleepwalking?

Matthew Walker (167:15)

No. So sleep walking, sleep talking. They're a group of disorders called parasomnias, which sort of essentially means just disorders that happen around sleep. Para meaning around sleep walking, in sleep talking actually don't come from REM sleep. You would imagine that they do. And it's a very logical thing. In fact, what happens is that when we are in deep sleep, for reasons that we don't quite yet understand, but it may be that there's a jolt of nervous system activity and all of a sudden your brain races, or it tries to race from the basement of deep sleep all the way up to the penthouse of wakefulness, but it gets stuck somewhere in between, like the 13th floor, for example. And what's strange, and we can do this in the sleep laboratory where we've got these electrodes and what we're seeing outside in terms of the brainwaves is deep sleep. But when you look at the camera, all of a sudden the patient is out the bed and the sort of, you know, the sort of moving around. And so if you wake someone up who's having a sleepwalking or sleep talking event and you say, you know, what was going through your mind, they usually won't tell you anything.

Rich Roll (168:25)

Right.

Matthew Walker (168:25)

And the reason is because they're in deep sleep, they're not in dream sleep.

Rich Roll (168:28)

That's so interesting. Yeah, I have some epic sleepwalking stories from when I was a kid. Yeah, I went out, I got up in the middle of the night and went outside in the middle of a thunderstorm and like, walked a block away from the house until my dad discovered what I. And I woke up standing in the middle of the street in a downpour.

Matthew Walker (168:47)

There are some remarkable case studies, you know, some of which I discuss in the book, where people have these episodes and some, you know, some dangerous and some unfortunate things really happen in those.

Rich Roll (168:59)

But then I just grew out of it. Like, how normal is that?

Matthew Walker (169:02)

It's very normal. So the incidence of sleepwalking and sleep talking is far higher when we're kids. And most adults will grow out of it. Not all adults, but most adults will grow out of it. And it's not really a sleep disorder necessarily, I think. You know, and again, I'm not, you know, I'm not a clinician, so. And I'm not trying to put. Pretend to be a sort of a doctor in any means, but I think the general advice is if it's not causing you distress and it's not putting you in harm's way, then one may not need to worry about it if it's sort of infrequent, but if it is causing you distress and it is putting you in harm's way, then you can go see your doctor. And I should note, by the way, something too on those sort of five tips, and I should mention, walk it out, just which is the last one. You know, none of those tips are really going to help anyone who has insomnia or, you know, sleep apnea. It's like me being, you know, your performance coach. I can give you all sorts of tips to optimize your performance, but if you've got a broken ankle, none of those tips are going to help you. We've got to get you to a doctor, treat the broken ankle, and then we come back to sort of optimizing your sleep. So the tips I'm giving are just that.

Rich Roll (170:18)

Right, I understand. But what percentage of people are truly insomniacs versus people who have habits that prevent them from getting a good night's sleep and call themselves insomniacs?

Matthew Walker (170:30)

It's actually very difficult to tell because part of the treatment for insomnia, which is now no longer sleeping pills, the first line treatment has to be something called cognitive behavioral therapy for insomnia, or CBT I for short. One of the things that works towards, as you can tell by the name, cognitive behavioral. There is an aspect where we work on the mind and we work around, you know, your beliefs and your expectations and your understanding of sleep. That's the cognitive part of CBT I. The behavioral part is actually asking what behaviors are you engaging in that are harming your sleep? And what things are you not doing behaviorally that can help your sleep? Alcohol, caffeine, regularity, light, et cetera. So those do play a role, but usually it's much more of a combination of different things. With cbti, it's much more extensive than that. It's just as effective as sleeping pills in the short term, much more effective in the long term. Unlike sleeping pills, when you stop working with your therapist, the benefits of cbti, Cognitive behavioral therapy for insomnia last for up to five years. But for sleeping pills, when you stop using them, not only do you typically go back to the bad sleep you are having, you actually have even worse sleep. It's called rebound insomnia caused by these sleep medications.

Rich Roll (171:46)

Yeah. I have friends who are in recovery for Ambien and the stories they tell are just harrowing.

Matthew Walker (171:53)

Yeah, yeah. And you know, there is a time and a place for those medications. They're usually recommended for acute, short, short term, significant episode. So let's say that you're really struggling with a trauma or bereavement or something along those lines. Then in combination with therapy, they can be advised for short term use. The problem is most people aren't using them in a short term use model. You know, and I, the reason, in part, I know this is I think it took George Lucas about 30 or 40 years, years to amass something like 2 billion in profit from the Star wars franchise. Took ambien less than 24 months to do that.

Rich Roll (172:35)

That's so true every time.

Matthew Walker (172:37)

You can't do that with acute use. So again, sleeping pills have been associated with high risk of death as well as cancer. Do we know that that's causal or not? No, we don't right now. And I can make an argument as to, to why it may not be causal, but I can also make a scientific argument as to why it is causal. We probably won't ever find out because based on the association between mortality risk and things such as cancer and sleeping pill use, it's probably going to be unethical to do a study where you put people, healthy people, on sleeping pills for several years because of the risk.

Rich Roll (173:15)

Yeah, no way. There's no way you could ethically justify, justify that.

Matthew Walker (173:19)

No.

Rich Roll (173:20)

Yeah, we've been going almost three hours. But I can't let you go. I do want to ask you, before I let you go, I know that you work with Google and I'm interested in.

Matthew Walker (173:32)

I used to work with Google.

Rich Roll (173:33)

Oh, you, you used to. Okay. In, in that capacity, were you able to help them implement certain policies like what, what kind of transpired there in terms of the work culture that was going on and, and the impact that your work had on that culture.

Matthew Walker (173:49)

Yeah. So I was actually working with a part of Google that was called Verily, which is sort of, that was the Google Health arm.

Rich Roll (173:58)

And so, so it wasn't focused on.

Matthew Walker (174:00)

So it wasn't really focused on going into there and changing the culture. It was more about sort of, you know, developing either technologies or it was also, you know, they have some remarkable cities in their public about this. So there's some aspects that I can share where they're looking at how things such as sleep impact different aspects of human health. So they're doing wonderful things in trying to augment things like diabetes risk, cardiovascular risk. And so I think what they realized is that when you're looking at all of these disease states, based on everything that we've spoken about for the past three minutes, which now is now three hours, talking about time dilation.

Rich Roll (174:40)

Right. We're having our own inception here.

Matthew Walker (174:42)

Yeah, we are really.

Rich Roll (174:44)

We are dreaming.

Matthew Walker (174:46)

I think I'm gonna wake up and the alarm goes off. And I thought, oh, I'm so sad. I thought I was on the Rich Roll podcast.

Rich Roll (174:52)

It's tomorrow.

Matthew Walker (174:52)

Yeah. And so knowing how critical sleep is, you know, the foundation, they realized that there had to be some component of sleep appreciation within that foundation framework of everything that they were trying to do. So I was so fortunate enough to be able to do that, and I no longer work with them. I've got a couple of startups that I'm now advising and working for. And so that was really, I think, the push there, which was that sleep is the tide that rises all the other health boats. And I remember when I was sort of speaking early with them, I almost had this analogy where if you think about a music studio and those recording decks with all of those dials and you can sort of mix and just sort of tweak them. What we're doing in health is trying to sort of go to individual dials. We're trying to manipulate cardiovascular health or change immune health or change, you know, metabolic and diabetes health. But there's that one sort of dial all the way over to the left that if you move it all the way up, all of the other dials go up as well.

Rich Roll (175:58)

The master dial, that's sleep.

Matthew Walker (175:59)

Sleep is the Archimedes lever. You know, if I think, if I were to have something, a single sentence, I would say that sleep is the single most effective thing that we can do each day to reset the health of our brain and our body.

Rich Roll (176:16)

That would be a beautiful place to end this. But I just realized there's an important thing we also didn't talk about that I would like you to touch on quickly.

Matthew Walker (176:23)

Yeah, of course.

Rich Roll (176:24)

Which is you talk. Talked at the outset about what happens when you get a flu shot and you're sleep deprived. We're still in the midst of this pandemic. We're slowly emerging out of it. But can you talk a little bit about what you've learned about sleep Covid immunity and how people should be kind of thinking about their relationship with the virus.

Matthew Walker (176:47)

Yeah. So I'll speak about sleep and immunity sort of more generally, and then come on to sleep and Covid. Because sleep has changed in at least four different ways because of COVID quantity, quality, timing and dreaming. So I'll try to mentally put those stickies up on my cerebral wall so I come back to them. But in terms of sleep and immunity, there is a very intimate association between your sleep health and your immune health. Firstly, what we know is that individuals who report sleeping less than than seven hours a night are almost three times more likely to become infected by the rhinovirus, which is the common cold. Second, we know from a prospective study in, I think it was well over 30,000 women, women sleeping five hours or less a night are more than 60% more likely to develop pneumonia across a five year period, which of course is a critical part of the COVID mortality equation. We've also mentioned that statistic about if you're not getting sleep in the week before you get your flu shot, you can't produce the normal antibody response. Do we know that that's the case for Covid yet? No, we don't, but we're looking at that. We also know it's the case for Hepatitis A, hepatitis B vaccination too. So I think there's an interesting case to be made that it could make a difference. We also know that just as we mentioned before, just one night of short sight sleep, you know, just four hours will drop those critical anti cancer fighting cells, natural killer cells, by 70%. If that's true, then what is sleep doing for our emotional health and sleep provides us two different benefits. Firstly, it's during sleep and particularly during deep sleep, where the body will be stimulated to produce many more of those critical immune factors. Even better, the sleep will actually increase the sensitivity and the receptivity of your body to those increased immune factors. So you wake up the next morning as a more robust immune individual. Sleep will restock the weaponry in your immune arsenal. So on that basis I, I think sleep has become very relevant in this pandemic. How has sleep changed right now? Well, as I mentioned, firstly, the studies show on average, which may be surprising to some people, sleep duration has actually increased somewhere between about 20 to 30 minutes. If you look at the handful of studies that are, people aren't commuting, not commuting, you don't have to get kids to school. So that's the first issue. Now if you look at that data a bit more closely, it's not that clear, it's not that clean cut or straightforward. There is a cloud of data of people for whom sleep has actually become worse. People have lost their jobs, people don't know if they will still have their jobs. People are just very Anxious about the pandemic. All of those things will decimate sleep, of course. So sleep quantity has changed, sleep quality has changed also. But we also know that sleep timing has changed. How are you getting that extra sleep? Well, people are going to bed a little bit later, but they're waking up significantly later. And I think this comes back to our discussion of chronotype now Covid, because we don't have to commute and wake up or do early morning meetings or get the kids to school, many people have been able to sleep back in synchrony with their natural chronotype. You know, it's revenge of the night owls in that way. And then the final component is that people, and I think we don't yet have enough data, but there's too many people saying this, that they were dreaming more and dreaming more about COVID Why would this be? I think there are two logical explanations. The first, just as we mentioned before, the later that you sleep into the morning, the more you go into that REM sleep rich phase. So you're just giving yourself probabilistic chance statistically of having more dreams. But I don't think that's the entire explanation. We also have spoken about this idea that REM sleep provides this form of emotional first aid. It's overnight therapy. In fact, there's an American entrepreneur, E. Joseph Kossman, who had this lovely. He said that the best bridge between despair and hope is a good night of sleep. And I think when we're going through these, you know, difficult emotionally upheaval time of a pandemic, no wonder the brain is trying to self medicate it. You know, this emotional situation with the thing that it knows provides a nocturnal soothing bomb, which is this thing called REM sleep, sleep and dreaming. And I think that's probably another explanation as to why we're not just dreaming more, but we're dreaming about the pandemic.

Rich Roll (181:48)

Itself, trying to make sense of it, trying to process it, trying to figure out a way to kind of have a healthier relationship with it.

Matthew Walker (181:55)

That's right, yeah. It just, you know, sleep divorces some of the emotion from the memory so that you come back the next day and you feel better about those emotional experiences. Because sleep has essentially stripped the bitter emotional rind from the informational orange. So it's not as though you wake up the next day and you don't remember that emotional experience. You do, but it's no longer as emotional itself. And so it's not time that heals all wounds, it's time during sleep and specifically dream sleep that provides emotional convalescence.

Rich Roll (182:34)

On the immunity subject, it would be interesting to do an evaluation of people that got Covid, how severe their case of COVID was and track that onto their sleep habits and patterns.

Matthew Walker (182:46)

People are doing that and we're looking at that. We're also looking at when you get vaccinated, what are the consequences? Some people are describing disruptions to their sleep. Usually what will happen is that you will have some degree of fever or when you go into fever, that increases your core body temperature. When your body temperature increases, you're not going to get good sleep. There are some devices that are now, and I wear the OURA ring sleep tracking device. And full sort of disclosure, I advise the company, so take anything I say with a grain of salt. But I was wearing the device for two. I've worn just about every sleep tracking device and it was just the one. That for me was a sticky device and I liked it. So I was wearing it for two years before I decided to join the company. But they have a fascinating model, what they've been able to find, because the OURA ring, unlike many of these other sort of devices, it tracks temperature. And what they were finding is that in some people who then went on a day later or two days later to find out that they tested positive for Covid, there was this spike in their relative temperature.

Rich Roll (183:52)

Yeah.

Matthew Walker (183:52)

And so, you know, we're now starting to explore this idea that it could be a useful diagnostic tool. Preemptive. Exactly.

Rich Roll (184:00)

I mean, I've got the whoop on. And they manage that not through temperature, but through metabolic rate.

Matthew Walker (184:05)

Yeah.

Rich Roll (184:06)

And they have some interesting science on that as well. So it's cool how these wearables are sort of developing and how the technology is evolving, but I think we're only beginning to understand, like the significance of that. They can play.

Matthew Walker (184:18)

Yeah, exactly. You know, I think I mentioned this invasion of technology into the bedroom and it has been a deleterious force. But perhaps unlike some other sort of sleep scientists, I'm not puritanical about technology. You know, that genie is out the bottle and it's not going back in anytime soon. So if you want to rail against it, you'll lose. But what we're now seeing is this beautiful sort of cycle where technology is starting to solve some of the problems of technology. And it's like that light in the matrix, you know, programs, hacking programs, and it's technology starting to hack the ills of technology. So I do think that wearable technology has a part to play and a place in our subsequent future health, this idea of personalized medicine. And for me, I'm interested in personalized sleep medicine. That's why I'm trying to sort of develop some of these companies. But I also think we need to. To be a little bit careful. There's now something called orthosomnia, which is a sleep disorder caused by obsessive sleep tracking, where you become so anxious. And so now it seems to be maybe 10 to 15% of the people who are using these suffer from. Or by the way, ortho means straighten in medicine. You know, you've heard of orthopedics, orthodontics, straightened teeth, straightened bones. Here it's about people getting too concerned about getting their sleep straight.

Rich Roll (185:35)

Yeah.

Matthew Walker (185:36)

Orthosomnia.

Rich Roll (185:36)

Yeah, yeah. I mean, 100. I mean, I think they're, they're just tools. It's about your relationship to them. But if you become obsessive about them, they work across purposes with their intent. Like, yeah, I know there are certain days where I'm not sure I really want to look at whatever the whoop score is because, like, I got stuff to do and if it says, like I'm not ready for it, that's going to screw me up. Like, I just would rather, I'll check it later. I use them as I think for me, my relationship to them is more in the macro. Like, I can look at trends over time, or I play a game where I wake up in the morning and I'll think, I'm pretty sure, here's where I'm at, and then I'll check it. And that helps me calibrate my intuition around these things. And the more intuitive you are about them, the less reliant upon them I think you become. But you have to hold them a little bit lightly.

Matthew Walker (186:24)

I love that. I think that's such a beautiful way of thinking about it. Often what I will say to, to people when they say, look, I had this really bad night of sleep and I don't want to look at my ring. Firstly, everyone has a bad night of sleep. Don't worry about it. It's not the end of the world. The second thing, when it comes to trackers of any kind, and particularly with sleep, follow weekly or monthly trend lines, don't follow nightly headlines, don't worry about those things. And I think the reason I, I believe sleep tracking is perhaps a little bit different than other aspects of health wearable tracking. When I go to the gym, I kind of know if I got a good workout in or If I didn't and when I'd be eating throughout the day, I know if I've been eating clean and in a healthy way or.

Rich Roll (187:10)

If I haven't, you don't want to score on that.

Matthew Walker (187:12)

And I think I probably will know it. And some days I'm ashamed of it. But what's interesting about sleep is that for the most part, it's a non conscious process. And so if I were to ask you, Rich, last night, how did you sleep? You can tell me. But if I said to you, rich, how did you sleep last Tuesday by yourself? You probably don't know. But that's where I think the power of some of this technology, it can identify trends and patterns and if we can start to measure those and then intervene to give people useful tips as to what they should do in a personalized manner because everyone is sleeping poorly for different reasons, that's really where we unleash the power of these things.

Rich Roll (187:53)

Matt Walker, we got to end this thing. So great talking to you. Will you come back and talk to me again sometime?

Matthew Walker (187:58)

If you would have me. And if your listeners don't lose the will to live because of my inane voice, I would be delighted to come back.

Rich Roll (188:06)

You are a gift, my friend. The work that you're doing, I think is super important. It's a privilege and an honor to help amplify it a little bit. So I really appreciate what you do. It's a great act of service to humankind. So thank you for that and thank you for spending the afternoon with me.

Matthew Walker (188:23)

I say exactly the same thing back to you based on what you're doing. Your honesty and your vulnerability of story has impacted people. I know. And what you're doing with this movement around, this podcast and empowering people with mind, body, guidance and information I think is fundamentally critical. So you are a gift. And now I anoint you as a sleep ambassador as well.

Rich Roll (188:46)

Rick.

Matthew Walker (188:46)

Thank you.

Rich Roll (188:47)

Now the pressure. I'll have a terrible night of sleep tonight.

Matthew Walker (188:51)

Just call me, put me on speed dial. I'll help you.

Rich Roll (188:55)

I'm going to call you every night. Am I doing this right?

Matthew Walker (188:57)

Yeah, don't worry. I will be right there for you. Thank you so much for having me, Rich.

Rich Roll (189:01)

Thank you. You can find and learn about matthew@thesleepdiplomat.com yes, Sleep Diplomat.

Matthew Walker (189:08)

Or if you want, you can read the book which is called why We Sleep. You don't have to read the book, you just have to buy it is what the publishers tell me.

Rich Roll (189:16)

No, you gotta read it.

Matthew Walker (189:17)

No, just buy a used copy.

Rich Roll (189:19)

I changed my life.

Matthew Walker (189:20)

I'm not interested in monetary stuff, but if you're interested in learning more about sleep, the book is a good way to do it.

Rich Roll (189:26)

Good. Well, let's do this again sometimes.

Matthew Walker (189:29)

I hope so. All right, thank you, Rich Peace Blitz.

Rich Roll (189:40)

That's it for today. Thank you for listening. I truly hope you enjoyed the conversation. To learn more about today's guest, including links and resources related to everything discussed today, visit the episode page@richworld.com where you can find the entire podcast archive my books, Finding Ultra Voicing, Change and the Plant Power Way, as well as the Plant Power meal planner@mealplanner.richroll.com if you'd like to support the podcast, the easiest and most impactful thing you can do is to subscribe to the show on Apple Podcasts, on Spotify and on YouTube and leave a review and or comment. And sharing the show or your favorite episode with friends or on social media is of course awesome and very helpful. This show just wouldn't be possible without the help of our amazing sponsors who keep this podcast running wild and free. To check out all their amazing offers, head to richroll.com sponsors and finally, for podcast updates, special offers on books, the Meal planner, and other subjects, please subscribe to our newsletter, which you can find on the footer of any page@richroll.com Today's show was produced and engineered by Jason Cameolo. The video edition of the podcast was created by Blake Curtis and Morgan McRae with assistance from our Creative Director, Dan Drake, content management by Shana Savoy, copywriting by Ben Prior, and of course, our theme music was created all the way back in 2012 by Tyler Pyatt, Drew Trapper Pyatt and Harry Mathis. Appreciate the love, love the support. See you back here soon. Peace Plan.