Brian Johnson (4:44)

There was this reporter that wrote an article recently for gq. I was at this anti aging conference and this person who interviewed me said, what is the number one thing you do for anti aging? And this reporter, she told the story. So people are there listening. What's Brian Johnson gonna say about this thing? Is he gonna say some peptide or Sano or whatever protocol? And then he says, sleep? And she said, then the crowd just has this collective sigh of disappointment.

Chris Hemsworth (5:14)

Right. Because it's much sexier to talk about rapamycin.

Brian Johnson (5:17)

Yeah. Whether that was true or not. But she was just like. Everyone was so disappointed with my response. But, you know, like, I don't know how to communicate more. Everything revolves around sleep. Nothing changes existence more than sleep. You have more willpower, you have more zest for life, you have more energy. Yeah. I just. Everything falls apart without sleep. I don't know how to communicate any better.

Chris Hemsworth (5:41)

Yeah. And when people want to hear you elaborate on that, the focus tends to be on the blackout curtains and the type of sheets and the air purifier that you have in the room and.

Rich Roll (5:51)

The temperature of the room.

Chris Hemsworth (5:52)

And those are all Fine and well and important and play their part. But to really appreciate it, you have to actually embrace the entirety of the program.

Brian Johnson (6:03)

Yeah, yeah, exactly right. I mean, I think we're all competing for status and power in society, you know, like in all of our own little circles and places. And there's so much mythology caught up in the hero being sleep deprived and sleeping under the desk and going days without sleeping. It's so built into the psychology that people are trying to signal to others, I'm worthy of being respected. I'm worthy of this status. I'm worthy of being admired. I'm worthy of this mythology. So they're doing things to play the script because they think it generates the respect of others. And in their mind, they may believe it too. Like, this is how genius is achieved. I can think of so many examples of people who've done this. And so it's so deep in our psychology that sleep deprivation is somehow positive, that that's what stops most people from adopting it.

Chris Hemsworth (6:53)

That hustle porn culture and notion of sleep is in its twilight. Like, I feel like we've really gone a long way towards raising awareness around that. Like, that's shifted a lot even in the last couple years. I think.

Brian Johnson (7:07)

I concur. Yeah. Just even, like, when I talk to my friends, they'll come to me and say, like, I want this so badly. We have to engage in a therapy session where I'm like, what's up? How's it going? And then we dig into, deep into their psychology and they uncover and unravel that they really are trying to be on mythology level with their levels of accomplishment. Now, it takes a lot of vulnerability for the person to be that honest. But, like, once we do that in private and they're like, oh, my God, this is totally unnecessary. I can achieve my objectives of ambition and status and power and wealth and success, and I don't have to do this sleep deprivation thing. And it's so liberating for them. They actually become better at their craft.

Courtney Peterson (7:49)

These circadian rhythms are primarily affected by two external cues in our environment. There's two things that can really throw them out of whack. One is light exposure. So if we're sitting up late at night in very, very, very bright lights, it's, let's say it's 9pm our body, and it's dark outside our body. We might be sitting in la, but our body thinks we're in Sydney. So we can cause some dysregulation of our circadian rhythms, and then that affects the Release of melatonin, which has an effect on your sleep, for example. We can also dramatically affect these circadian rhythms through the timing in which we eat. That's the other really important signal here. So within this challenge, we have two different habits that speak to nurturing our circadian rhythms. One is light exposure. We want people in the morning to get outside, get at least 10 minutes of natural light exposure in the first couple of hours of waking up. That's important. That sets your clock.

Chris Hemsworth (9:09)

This is the Huberman protocol around morning.

Courtney Peterson (9:11)

Sunlight and then at nighttime as the sun's going down. Ideally, you don't have to turn all the lights off in the house, but it will be helpful if you dim the lights down. And if you're using screens, you can adjust the brightness on those and put them into night mode. And then with regards to the timing of our food, there's some really interesting research that has come out of Courtney Peterson's lab. I interviewed her looking at how efficiently is our body utilizing nutrients at different times of the day. And it seems that particularly at nighttime, a couple of hours before we go to bed, we have changes in hormones that make things like glucose metabolism much less effective. It makes sense. Our body is getting ready to go to sleep, not to digest food and convert it into energy. The ideal kind of eating window, and some people have described this as a circadian biology eating window or circadian fasting. I don't think it's really a crazy fast, is you're in bed for eight hours a night. That's what we said just before and when you wake up, not eating for one or two hours upon waking. And before you go to bed, not eating for one or two hours before you go to bed, before you go to bed. Now, if you. Let's say you do that as two hours. So you're in bed for eight. You don't eat for the first two hours of waking up. And then before you go to bed, you're not eating in the two hours leading up to bed automatically. That means your eating window is at 12 hours. The average person's eating window in America is 15 to 16 hours. So pretty much rolling out of bed, having a bite of a donut, and hitting all the way up to going to sleep again. The reason why all of this is important is that we know that this chronic circadian disruption significantly increases risk of metabolic diseases, significantly increases risk of obesity, of cardiovascular disease. So there are repercussions if we're living in a way where our circadian rhythms are disrupted and it's not just the long term. If you're experiencing chronic circadian disruption, you're likely to feel more brain fog, more fatigue, less lower energy or lethargy on a daily basis. So just getting some routine in place where we're in bed for eight hours, which thinking about light exposure, and then we're eating at a regular time, trying to avoid eating too close to waking up or going to bed can make a very big difference.

Chris Hemsworth (12:23)

This is like my Mount Everest because I get so hungry at night, man, it's very difficult for me to not eat in the two hours before I go to sleep. Like, that is my Achilles heel. So if I accomplished nothing other than figuring out how to master that as a result of doing this challenge, that would be a huge win for me.

Courtney Peterson (12:46)

Have you played around with the types of food that you're eating?

Chris Hemsworth (12:49)

Yeah. And, you know, when I was wearing a continuous glucose monitor, it was very evident, like, when I would eat, like, right before going to bed, how it would wreak havoc on me. And, you know, I would wake up in the middle of the night and stuff like that. And my blood glucose regulation is, you know, super dysregulated as a result of that. Like, I know I shouldn't do it, and I. It's just this is a habit that's been very difficult for me to break.

Courtney Peterson (13:20)

I haven't seen this formally studied, so I can't speak to an intervention. But I have a hypothesis here, and I'm not sure whether you've tried this, but I'd be interested to see what happens if you have a slightly lower carbohydrate dinner and higher fat. And I suspect because that will be slower to digest and metabolize, that you might feel fuller for longer.

Chris Hemsworth (13:47)

It's a weird satiety thing, and I don't know if it's just mental or emotional, but if I don't feel full when I get into bed, like, I feel, like, agitated. You know, I feel like I need to. There's something emotional or physiological about, you know, how you kind of relax when you have. When you. When you've just eaten, like, your anxiety and your stress level lowers. And for some reason, if I'm going to bed and I'm hungry, like, it becomes very difficult for me to fall asleep.

Courtney Peterson (14:21)

I get that you might need a bigger. Bigger plate at dinner.

Chris Hemsworth (14:24)

I eat plenty. Trust me, dude. Anyway, I don't want to get too sidetracked on that, but I think that's really important, and that's great. And if you want to be more rigorous about your sleep tracking. There's always, you know, like a whoop or something like that that you can get that, you know, listen, I never take this thing off. And it's really been helpful in keeping me on track. Not so much for the day to day, but more for the trends and just understanding the types of behaviors and habits that influence things like HRV and the amount of REM or deep sleep that I'm getting every night and how impacts resting heart rate, stress, like all those sorts of things, like just, it's just information that arms you with the data points to kind of solve the arithmetic of what works for you and what's leading you astray.

Courtney Peterson (15:16)

Yeah, I love the sleep data. And you know, I agree. I've been able to identify a few different kind of patterns I've noticed if I'm, if I'm working really late, then my restorative deep sleep is much lower. Probably going to bed thinking about things.

Chris Hemsworth (15:37)

And then if you correlated that with what your, where your stress levels are and how long it takes them to go down as you go to sleep, because if you haven't reduced those before going to bed, you're going to have a less restful evening of sleep.

Courtney Peterson (15:51)

Yeah, my Recovery today was 86%.

Chris Hemsworth (15:54)

That's pretty good.

Courtney Peterson (15:55)

I was happy with that.

Chris Hemsworth (15:55)

Yeah, right on.

Andrew Huberman (15:58)

One thing that's clear from the work on sleep that's now working its way into the naming and understanding of brain states and wakefulness is that one state precedes another. Now, your bike ride, where you're listening to the audiobook, is a way in which you're coordinating your respiration physiology, your breathing and your motor output. Your bike riding with the ability to access auditory information and remember it well. So you've figured out something about that state. But the neuroscientist in me says, okay, but what follows that state when you get back? What state are you in then? Is it a state of exhaustion that allows you to go into deep rest to access neuroplasticity? Or is it a state of where you've essentially moved all that excess autonomic arousal out of your body and now finally you can sit down and just focus your cone of attention on your work? So one state precedes another. And one thing that I think can be incredibly useful to people would be to think about two hallmarks of brain states in order to access them more readily. One is that the thing that we are all a slave to, all of us, is the 24 hour circadian cycle. Every cell in our body has a 24 hour clock that runs at the level of genes and the level of cellular processes and every network in our body, whether or not it's nervous system, spleen, whatever, is governed by this 24 hour clock. We can fairly crudely, but still accurately subdivide that 24 hour period into three phases. What I would call phase one, and I'm just naming it phase one because we don't have a better name for it, is from about zero until about eight or nine hours after you wake up. Phase two is from about nine hours after you wake up until about 16 hours after you've woken up. And phase three would be from about 17 hours to 24 hours. The 17 hour to 24 hour period that we're calling phase three is sleep. And we know what we should be doing in that state. We should be accessing as much uninterrupted deep sleep as we can. And the beautiful work that Matt's done and others have done says, okay, lower the temperature in the room, elevate your feet a little bit, et cetera, et cetera, keep it dark. I mean, there's a lot of things that we could talk about there. Phase one and phase two, we know based on really good neuroscience, have certain signature patterns of neurotransmitter release and autonomic arousal that lend themselves better to certain activities, both mental and physical, and not others. So phase one, for instance, is always accompanied by an increase in cortisol. This is a healthy release of cortisol, a stress hormone that wakes us up. It's part of the wake up system and the release of epinephrine, which is also called adrenaline and the molecule dopamine. It turns out epinephrine and dopamine. Dopamine actually manufactures epinephrine. They're biochemically so that phase one of the day in many ways is ideal for any kind of linear, action oriented items. If you had. People will differ. Some people say I do creative work best early in the day, but most people are going to do best at kind of correct answer type work, meaning where there is a correct linear output. It's going to be accounting type work or it's going to be exercise, where you might not know exactly what you're going to do, but there is a process that you can follow. It's going to be punching out a certain amount of words on a page because you're just trying to get the words down on the page for the book, or doing math or doing any kind of linear operations during that first Phase one, Phase two, has a signature pattern of neurotransmitter release in the brain and body that are more closely associated, not exclusively, but more closely associated, with the release of things like serotonin. These are neuromodulators that tend to make us feel a little bit calmer and they disrupt, or I should say they alter, because it's not a pathological shift, but they alter our perception of space and time in a way that allows us to make mental associations that are a little bit looser, they can be non linear. So that's a time that's excellent for creative work or for brainstorming. And you might notice that when you're a little bit fatigued, your mind is a little freer. And if you're very fatigued, your mind is all over the place. So one thing that I think has been missing from the brain state work has been a kind of cohesive framework. And yet everyone, I think every neuroscientist would agree that the 24 hour cycle really governs not just digestion and bodily temperature, because it does. Temperature is higher in the morning, rising, rising, rising to the afternoon, then starts coming down, and then you go into sleep and phase two, because your body temperature is lowered. So those three phases really drive our brain states, and one precedes the other. This is the key thing. We can never look at a state in isolation. But if you wanted to understand, for instance, how to access a state of heightened creativity, you might try placing it in phase two of the day. So 10 to 16 hours after you've been awake and see how that works for you. And pay attention to your state of mind before you attempt to go into that state and as you exit that state. And so I think that if we've learned anything from the sleep science, it's that we can't look at one state of mind in isolation. We need to ask what preceded it and what follows it in order to understand its structure and how to access it better.

Rich Roll (20:58)

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Chris Hemsworth (21:46)

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Rich Roll (21:47)

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Matthew Walker (24:04)

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 has a profound story to tell in our understanding, our treatment, maybe even our prevention of grave mental illness.

Chris Hemsworth (24:58)

Well, certainly in saying that it should be the first stop on the kind of treatment protocol.

Rich Roll (25:04)

Right.

Chris Hemsworth (25:04)

Like how is your sleep? Let's deal with that first before we look at pharmaceutical interventions.

Matthew Walker (25:09)

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.

Chris Hemsworth (25:33)

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

Matthew Walker (25:37)

Oh, I'm so sorry.

Chris Hemsworth (25:39)

No, no, it's really bad. 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 (26:06)

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, a 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.

Chris Hemsworth (27:31)

Statistically unbelievable.

Matthew Walker (27:33)

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. When sleep is abundant, minds flourish. When it's not, they don't.

Chris Hemsworth (28:19)

Right. There's so much education, I think, that needs to be done in this area. As a parent of, 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 gonna 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 (29:22)

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 couch, saying, you know, you're wasting the day, you know. 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 asking 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 I was to wake up at 3 o' clock in the morning and come through to the kitchen or we were both awake, I'd have to say to my partner, you know, I would say to her, look, darling, 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. They are at that stage they are leaky sieves and what will 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 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.

Chris Hemsworth (31:58)

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

Matthew Walker (32:04)

They do.

Chris Hemsworth (32:04)

So the eight hour rule doesn't really apply.

Matthew Walker (32:07)

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. 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, a 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.

Chris Hemsworth (34:39)

And it is decoupled on some level from the food coma, right?

Rich Roll (34:43)

Correct.

Chris Hemsworth (34:43)

Part of it is, oh, I ate a big lunch. But this is independent of.

Matthew Walker (34:47)

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

Chris Hemsworth (34:56)

Right. So siesta.

Matthew Walker (34:58)

So siesta. 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 seven. Sorry. 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.

Chris Hemsworth (36:44)

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 (36:56)

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 can, 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. You know, 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 (38:34)

I want to talk about fasting, something I used to think about in binary terms like you're either eating or you're not, right? Well, if you're a longtime listener of this show, then you'll probably recall my conversations with Dr. Valter Longo, who if you don't know, is one of the world's preeminent research scientists on nutrition and longevity. And this is the guy who pioneered a very novel middle ground approach to fasting where you can actually nourish your body while also triggering cellular repair processes that happen during fasting. Like autophagy, a Nobel Prize winning cellular repair process that cleans house in your body and you get to eat while it happens. Which is nuts, right? And now there is a safe and simple way to do this at home, courtesy of Prolon's Fasting mimicking diet, a five day plant based nutrition program developed over decades at USC's longevity institute by Dr. Longo himself. It's got soups, it's got snacks and beverages that nourish your body while also keeping it in a fasted state. Prolon Next gen features include 100 organic soups and teas with richer taste. Everything prepackaged and ready to go. It supports biological age reduction, metabolic health, skin appearance, fat loss and energy. Prolon is the first and only patented nutrition program for longevity through cellular rejuvenation. For a limited time, you can be the first in line to experience the new next gen. At special savings, Prolon is offering all of you 15% off site wide plus a $40 bonus gift. When you subscribe to their five day nutrition program, just visit prolonlife.com richroll that's P R O L O N l I f e.com richroll to claim your 15% discount and your bonus gift. Prolonlife.com richroll I want you to pause for a moment because I want to tell you about my friend rj. Now you might know this guy as the founder and CEO of Rivian. He's certainly that, but he's really so much more. He's one of those rare people who actually walks the walk. I've watched him over many Years. And I know him to be this incredibly deeply committed person, committed to preserving wild spaces while also inspiring people to explore responsibly. And that's basically Rivian in a nutshell. Their mission, keep the world adventurous, us forever, comes from this understanding that adventure and a healthy planet, these are not separate things, they're the same thing. Here's what gets me. Every generation deserves wild places to roam, to climb higher, to run farther, to be changed by the journey. But obviously that's only possible if we're not destroying those places in the process of getting there. So yeah, Rivian builds electric vehicles, but really finally they're building something bigger. Momentum toward a future where exploration does not come at the expense of nature, but actually inspires us to protect it. It's like, why create the ultimate adventure vehicle if we're not protecting the adventures themselves? And that's why I'm so proud to align forces in partnership with Rivian. This isn't just about transportation. It's about building a world where worth exploring for our kids, for their kids and for generations to come.

Chris Hemsworth (42:06)

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, that have insomnia?

Matthew Walker (42:19)

Hard to get it across the blood brain barrier, which is a protective layer around the brain. And, and there's some issues around toxicity as well. So yeah, that certainly would have been the idea. But what's lovely is that 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 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, kumbaya and we all hold hands 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 and mindful practice, you can actually drop the severity of the insomnia in a way that medications, such as even prescription medications can't come close to.

Chris Hemsworth (44:16)

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

Matthew Walker (44:23)

Yeah, me too.

Chris Hemsworth (44:23)

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 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.

Matthew Walker (45:16)

Exactly.

Chris Hemsworth (45:16)

Literally short circuits that other anxiety producing narrative and I fall asleep.

Matthew Walker (45:23)

You're so right. So I think in this modern day and age, sort of empty fee, fast food 247 society, we're constantly on sort of reception, particularly with now all of this digital technology, and rarely do we do reflection. 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 don't want the Rolodex of anxiety spinning up, which is what you were sort of 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.

Chris Hemsworth (46:18)

But if you're catastrophizing it would probably be better to start counting sheep.

Matthew Walker (46:22)

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 it just drifted off because I've taken my mind.

Chris Hemsworth (47:22)

That's great. It's sort of a different version of what I do. What kind of car cars do you race?

Matthew Walker (47:26)

Oh, gosh, I've raced all sorts. BMWs, Porsches. But my real love and the car that I own is a little Mazda Miata. 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.

Chris Hemsworth (48:02)

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 (48:13)

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

Chris Hemsworth (48:18)

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, but 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. And we would have this back and forth over many years where it's too cold for her.

Rich Roll (49:45)

I'm on top of all the COVID.

Chris Hemsworth (49:46)

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. 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 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 (51:05)

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. Cause 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 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.

Chris Hemsworth (52:08)

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

Matthew Walker (52:10)

Right. Yeah.

Chris Hemsworth (52:11)

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, I. You found there is an inflection point at which point perhaps, you know, too cold is not so good.

Matthew Walker (52:26)

Yeah. Once you get into an extreme, it.

Chris Hemsworth (52:27)

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 (52:34)

Yeah.

Chris Hemsworth (52:34)

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

Matthew Walker (52:38)

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

Chris Hemsworth (52:41)

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

Matthew Walker (52:47)

Yeah. Do you know why?

Chris Hemsworth (52:48)

Yeah, I think I know, but go ahead.

Matthew Walker (52:51)

Yeah. 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're 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, of artificially terminating sleep with an alarm, they're perplexed. Also, 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.

Chris Hemsworth (55:20)

They're also moving all day long.

Matthew Walker (55:21)

They're moving all day long. And we can look at diet as well. So what is determining their sleep onset and their sleep offset? It's not light, it's temperature. And if you ask people, if you just bring them into the laboratory and you say 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, 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. I think many of us, even if we've got blackout curtains and sort of, you know, we're wearing an eye mask, we will wake up. And I think we have 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 clock, which may get you within one hour, plus or minus, 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 that's fascinating. You know, I love this. It's something, 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 in, you know, we're going to grab coffee and I've got to get this early morning flight from LAX. And you set your alarm for, you know, 5:00 in the morning and guaranteed you will wake up at 4, 58, 100%. How is that possible? It happens too frequently for it to be, you know, 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. 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 fold and compress time like a concertina.

Chris Hemsworth (59:16)

It's like Inception.

Matthew Walker (59:18)

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, were tiny, right?

Chris Hemsworth (59:36)

Like, so what do you make of that? Like, what would be the evolutionary advantage of that?

Matthew Walker (59:42)

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. 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. C cpap, the continuous positive airway pressure. 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.

Chris Hemsworth (61:43)

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

Matthew Walker (61:49)

We don't know. And it depends on what extent of atrophy. 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 back.

Chris Hemsworth (62:10)

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

Matthew Walker (62:12)

They never come back. Well, that's not true. There are in many regions of the brain that is true, but there are 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 demand 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, 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, you know, 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 underslept. 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 salvaging of that.

Chris Hemsworth (63:29)

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 at richroll.com, where you can find the entire podcast archive, my books, Finding Ultra Voicing, Change and the Plant Power Way. 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.

Rich Roll (64:03)

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Chris Hemsworth (64:04)

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Rich Roll (64:11)

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Chris Hemsworth (64:13)

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Rich Roll (64:36)

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Chris Hemsworth (64:38)

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Rich Roll (64:43)

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Chris Hemsworth (64:50)

Theme music was created all the way back in 2012 by Tyler Pyatta, Trapper Pyatt and Harry Mathis.

Rich Roll (64:57)

Appreciate the love, love the support.

Chris Hemsworth (64:59)

See you back here soon. Peace Plants Namaste.