Daylight Saving Time: Should We End It?

Summary

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Science Vs – Daylight Saving Time: Should We End It?

Host: Michelle Deng (filling in for Wendy Zuckerman)
Date: October 30, 2025
Duration (content): ~00:00–33:33

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Episode Overview

This episode of Science Vs investigates whether we should stop changing our clocks twice a year for Daylight Saving Time (DST). Host Michelle Deng, alongside senior producer Meryl Horne, dives into the history, intended benefits, and real-world consequences of DST. The episode weighs scientific evidence for and against sticking with either permanent Standard Time or DST year-round, asking: what’s healthiest, safest, and most practical for society?

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Key Discussion Points and Insights

1. The Origins and Persistence of Daylight Saving Time

[03:40 – 06:25]

• Origins:

  • Contrary to popular belief, DST was not invented for farmers. It originated as an energy-saving policy during World War I, first adopted by Germany.
    • Michelle Deng [04:19]:
      “It actually started as a government project to save energy…and this was back during the World War I years.”
  • The U.S. finalized the national DST schedule in the 1960s.

• Current Rationale:

  • Today DST’s benefits are debatable. Initially thought to save energy, modern research finds any savings are minimal to nonexistent.
    • Michelle Deng [05:20]:
      “One report from 2008 found we save half a percent of electricity per day…other studies find it doesn’t save energy at all.”
  • Economic arguments (e.g., retail and candy industries like more evening light) have promoted DST, but evidence is mixed about overall economic benefit.

2. Negative Impacts of the Clock Switch: Wildlife and Car Accidents

[06:26 – 13:52]

• Human-Deer Collisions Surge After Fall Switch:

  • Laura Prue, wildlife ecologist, studied deer-vehicle collisions across 23 states and found:
    • 2 million+ deer are hit in the U.S. yearly, mostly at dawn/dusk (“crepuscular” animal activity).
    • After “falling back” to Standard Time, when evening commutes occur in darker conditions, there is a 16% spike in deer collisions in the week after the switch.
      • Laura Prue [11:07]:
        “The switch in the fall led to a 16% increase in collisions. Just comparing the week before the switch to the week after.”

• Public Safety & Economic Costs:

  • These accidents aren’t just tragic for deer: ~60,000 human injuries and over 400 deaths per year in the US are due to such collisions.
  • Permanent DST could prevent 36,000 deer accidents, 2,000 injuries, and 33 deaths annually, saving ~$1.2 billion.
    • Michelle Deng [12:17]:
      “Having permanent daylight saving time could prevent over 36,000 deer car accidents a year across the US … 2,000 fewer injuries and 33 fewer deaths.”

• Other Species & Crime:

  • The collision problem extends to koalas in Australia.
  • Violent crime decreases with more evening light (robberies down 27% during DST).
    • Michelle Deng [13:31]:
      “There was one study that found … robberies went down by 27% when you compare daylight saving time to standard time.”

• Conclusion from This Data:

  • Strong evidence emerges for keeping DST all year, preventing accidents and crime.

3. The Circadian Clock, Sleep Science, and Standard Time

[17:12 – 25:53]

• Spring Forward, Heart Attacks, and Sleep Disruption:

  • The “spring forward” switch is linked to sleep loss, short-term cognitive impact, and possibly a spike in heart attacks and strokes (although new evidence is less conclusive).
    • Michelle Deng [18:13]:
      “The risk for heart attack and stroke goes up in the first two days.”
    • Jamie Zeitzer [18:15]:
      “That’s how fragile and vulnerable your body is to even just the smallest perturbation of sleep.”

• Circadian Rhythm Deep Dive (with Jamie Zeitzer, Stanford sleep scientist):

  • Early-morning light exposure synchronizes the body’s “internal clocks” in various organs, vital for metabolism, hormonal cycles, and general health.
    • Jamie Zeitzer [18:56]:
      “Bright sunshine closer to when you wake up is, in theory, going to strengthen your circadian clock…”
  • Regularity is key: erratic cycles (such as clock changes) weaken this internal synchronization and can negatively impact health (seen clearly in shift workers).
    • Jamie Zeitzer [21:40]:
      “If you have an erratic sleep-wake cycle…it translates to an erratic light-dark cycle, then you get a weaker clock.”

• Is Permanent Standard Time Healthier?

  • Standard Time best matches “solar time” and natural light exposure, potentially better aligning our circadian rhythms.
  • Sleep science and health organizations (American Academy of Sleep Medicine, Sleep Research Society) advocate for permanent Standard Time.
    • Michelle Deng [25:03]:
      “The American Academy of Sleep Medicine…all say we should be on permanent standard time.”

• But Where’s the Data?

  • Jamie Zeitzer critiques the lack of hard evidence.

    • Jamie Zeitzer [25:43]:
      “That’s what everyone’s been saying…‘according to the theory.’ Well, how about some data?”

  • He runs new studies, modeling health “burden” under three scenarios: current switching, permanent DST, and permanent Standard Time.

    • FINDINGS:
      • Both forms of permanent time are healthier than clock switches.
      • Of the two, permanent Standard Time results in slightly better outcomes for obesity and stroke prevention:
        • Preventing 2 million cases of obesity and 300,000 strokes if the country switches to permanent Standard Time.
          • Michelle Deng [28:54]:
            “We could potentially prevent obesity in over 2 million people… and prevent strokes in 300,000 people.”

4. The Messy Middle: Science, Policy, and Lived Reality

[29:55 – 32:41]

• No Simple Answer:

  • Everyone agrees clock changes are the worst option.
  • There is no clear consensus or “slam dunk” scientific answer about which form of permanent time is best for everyone.
    • Michelle Deng [30:01]:
      “It’s kind of funny…I thought there’d be a clearer answer here, but it’s messier than I thought.”

• Public Opinion Is Split:

  • Polls show US citizens are nearly evenly divided between permanent DST and Standard Time.

• Logistical/Nuanced Factors:

  • A universal solution is elusive—different locations within time zones may experience very late sunrises in winter under permanent DST.

  • A 30-minute compromise has been suggested but could introduce logistical headaches.

    • Meryl Horne [30:47]:
      “Can we just, like, split down the middle? … What if we did like 30 minutes?”
    • Michelle Deng [31:00]:
      “Some scientists have actually brought this idea up too…But…could you imagine the logistics of being a half hour offset from other countries…”

• Host’s Opinion and the Case for Caution:

  • Michelle Deng leans toward maintaining the status quo until the science is clearer.
    • Michelle Deng [32:07]:
      “I think controversial take, but I think we should stick with what we have now until the science is super clear.”

5. Practical Advice for Dealing with the Switch

[32:48 – 33:26]

• To blunt the negative effects of the clock change, Michelle recommends adjusting your sleep by small increments the week before:
  • Michelle Deng [33:09]:
    “Adjust your sleep time by 15 minutes a day the week before the actual switch…Basically, ease into the switches so it’s not a whiplash for your body.”
  • Meryl Horne [33:09]:
    “Seems kind of annoying, to be honest…”

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Notable Quotes & Memorable Moments

• On the Reality Behind DST’s Origins:

  • Michelle Deng [04:19]: “Interestingly, it has nothing to do with the farmers, but it actually started as a government project to save energy…”

• On the Dangers of Deer Collisions:

  • Laura Prue [11:07]: “That switch in the fall led to a 16% increase in collisions, just comparing the week before the switch to the week after.”
  • Michelle Deng [12:17]: “Permanent Daylight Saving Time could prevent over 36,000 deer car accidents a year across the U.S. … 2,000 fewer injuries and 33 fewer deaths.”

• On Sleep & Circadian Clocks:

  • Jamie Zeitzer [18:56]: “That bright sunshine closer to when you wake up is in theory going to strengthen your circadian clock.”
  • Jamie Zeitzer [20:24]: “You can kind of think of [the central circadian clock] like a conductor of an orchestra.”

• On the Lack of Concrete Data:

  • Jamie Zeitzer [25:43]: “That’s what everyone’s been saying. Oh, according to the theory. Well, how about some data? This is what I’ve been saying for years is I’d like to see some data. And no one ever shows any data.”

• On the Bottom Line:

  • Michelle Deng [30:01]: “It’s kind of funny. I thought there’d be a clearer answer here, but it’s messier than I thought.”
  • Michelle Deng [32:07]: “I think…we should stick with what we have now until the science is super clear.”

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Timestamps for Key Segments

• 00:00–03:21 — Introduction: The heated debate over DST and the science behind it
• 03:21–06:25 — Origins and economic/cultural arguments for DST
• 06:26–13:52 — Car accidents, crime, and animal welfare: Harmful effects of the fall time switch and arguments for permanent DST
• 17:12–25:53 — Sleep science, circadian rhythm, permanence of Standard Time, and health impacts
• 25:53–30:01 — New research: Modeling health outcomes of switching vs. permanent time; which is actually healthier?
• 30:01–32:41 — Public opinion split, logistical/equity issues, practical uncertainty
• 32:48–33:26 — How to make the transition easier each year

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Final Thoughts

This Science Vs episode highlights that:

• Clock switches are the most harmful policy: They’re associated with accidents, disrupted sleep, and potential health impacts.
• Permanent DST and Standard Time are both better than switching, but each has unique pros and cons, and science isn’t yet a “slam dunk” for either.
• Current science slightly favors permanent Standard Time for metabolic and cardiovascular health, but daylight in the evening offers measurable public safety and economic benefits.
• Public opinion and practicality are split; geographical differences complicate a “one-size-fits-all” solution.
• Practical tip: Prepare your body for the switch by gradually shifting your sleep schedule.

In short: The science points strongly toward abolishing the twice-yearly clock change, but which “permanent” time to pick is still up for debate.

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Transcript

[Michelle Deng]

Hi, I'm Michelle Deng filling in for Wendy Zuckerman this week and you are listening to Science versus Today. We're pitting facts against falling back and springing forward. Pretty soon a lot of us will be changing our clocks by an hour. And with this biannual ritual comes a chorus of haters.

[Jamie Zeitzer]

Daylight Savings time needs to die. Twice a year. I have to mess with my life and move the clock by one hour because of Daylight Saving Time.

[Michelle Deng]

I hate daylight savings. I just would like to have a moment of silence for how much daylight savings f up your day. A lot of people think it's time to say goodbye to these shifts. In fact, a handful of countries have already abolished the switches and, well, in the US hundreds of bills have been proposed to do the same.

[Jamie Zeitzer]

There's a new push in Congress to lock the clocks and stop our spring and fall tradition altogether. The Senate unanimously approving a proposal to make Daylight Saving Time permanent.

[Michelle Deng]

So a lot of people want to quit changing the clocks, but there's a lot of debate, like, yeah, having that sunlight in the evening after work is really nice, but people are saying it's bad for our health. Eeving dangerous that Daylight Saving Time could even kill you. Did you know the number of heart attacks increase right after Daylight saving changes?

[Commercial Announcer]

Having to wake up in the dark is not only uncomfortable, it's actually really bad for your health long term.

[Michelle Deng]

So today we're looking at the signs of springing forward and falling back and asking, should we get rid of these clock changes once and for all? And if so, what's better for us? Permanent Daylight Saving time or Permanent Standard time? Because when it comes to the switches, there's a lot of Daylight Savings time needs to die. But then there's science. Science versus Daylight Saving Time is coming up after the break. This episode is sponsored by Anthropic, the team behind Claude. Good science means understanding what studies actually show. How were participants selected? How do findings connect across research? Claude is an AI that works through these questions with you, helping you explore scientific methodology and build richer understanding of evidence. For minds that love discovering how we know what we know, try Claude for free at Claude AI Scienceverses and see why the world's best problem solvers choose Claude as their thinking partner. That's Claude AI scienceverses.

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[Michelle Deng]

Welcome back. Today on the show Daylight Saving Time. Is it bad for us and should we get rid of it? I'll be discussing the signs today with senior producer Meryl Horne. Hey, Meryl. Hey, Michelle. Are you ready for the fall switch? Not at all.

[Meryl Horne]

I hate Daylight Savings Time.

[Michelle Deng]

What part do you hate?

[Meryl Horne]

Mostly because I have two small kids. It's like you spend all this time trying to make their bedtimes, like, you know, go well and get them up for school at a certain time, and then it's like you suddenly remember, oh, crap, like everything has to happen differently tonight and either try to keep them up late or try to put them down early, which never works. And it's just a mess for that first few days.

[Michelle Deng]

You don't think you get that extra hour of sleep in the fall switch?

[Jamie Zeitzer]

No.

[Michelle Deng]

No. So, Meryl, why do you think we have Daylight Saving Time in the first place?

[Meryl Horne]

I mean, I've heard it's because of the farmers. Something to do with the farmers?

[Michelle Deng]

Because I also heard that before. Interestingly, it has nothing to do with the farmers, but it actually started as a government project to save energy, and this was back during the World War I years.

[Meryl Horne]

Wait, so it's only been around since World War I?

[Michelle Deng]

Yeah, it was conceptualized before that, but the first country to widely adopt it was Germany as a way to save fuel during wartime efforts.

[Meryl Horne]

Why would that save fuel?

[Michelle Deng]

Like, if you can extend the day and the sunlight, you can then save costs on working into the night, like light and energy. Okay. Other countries in Europe then picked it up, and so did the U.S. which finalized the national schedule for it in the 60s. Okay. But the kind of funny thing is that these days, Daylight Saving Time doesn't save that much energy. Oh. So, like, One report from 2008 found that we save half a percent of electricity per day of what otherwise would have been used.

[Jamie Zeitzer]

Oh.

[Michelle Deng]

And other studies find it doesn't save energy at all.

[Meryl Horne]

Once we realized that the fuel thing didn't make sense, why did we keep it? Is it just kind of tradition?

[Michelle Deng]

Yeah. So there's been some other big arguments to keep it. One, was the economy, like, this idea that if there's more light out in the evening, that people are more likely to go shopping, do their errands?

[Meryl Horne]

Oh, that kind of makes sense. Like, stores are open later in the summer in my neighborhood.

[Michelle Deng]

Yeah. And Interestingly, like retail, golf and sporting goods industries have all been big advocates for daylight saving time, as well as Halloween candy makers. Like, they really wanted daylight saving time to go over, like, trick or treating.

[Meryl Horne]

Hours, you know, so that people would be trick or treating in the light when it's like they can get more hours out of trick or treating.

[Michelle Deng]

Yeah, yeah, yeah.

[Meryl Horne]

Does it actually help the economy?

[Michelle Deng]

So there's studies on this too, and it's also. It's mixed. Whether it actually helps or not.

[Meryl Horne]

Even though the business people think it helps, it's not that clear that it's that good overall for businesses, it could.

[Michelle Deng]

Be helping particular industries. Right. But as a whole, for the economy, it's pretty mixed. Okay, so now that we know that the original reasons for daylight saving time don't make sense, let's find out if we should just get rid of it. Like, is daylight saving time actively causing harm to us? And I want to start with where we are now in the US about to fall back. So meet Laura Prue. She's a scientist at the University of Washington. And like you, she finds the fall switch pretty annoying.

[Laura Prue]

Especially in Seattle when it's dark and rainy at that time of year. Anyway, having it start to get dark at like 3:30 is really tough. You know, at the end of your work day, you leave work and oh my God, it's dark out already.

[Michelle Deng]

Yeah, it's so depressing. Yeah, I know. Like sad. We were just working for eight hours, but then everything we do after work is then in darkness. And a big part of our evening is our commutes home. You know, going to the grocery store, getting kids to school, activities, meeting friends. So traffic volume is definitely busier in the evening than in the morning. And this is where daylight saving time really intersects with Laura's work because she is a wildlife ecologist, but one of the species that she studies is deer. Oh. You know, there are tons of deer across the entire US and sure they're cute, but they can also be kind of a big problem for us because we're always out there hitting them with our cars.

[Meryl Horne]

Yeah. I feel like this is not gonna end well for the deer.

[Michelle Deng]

Have you ever had any run ins with deer?

[Meryl Horne]

No, but it's so sc. I know people who have, and it. It's so dangerous, like, for everybody if. If there's an accident with one. So it does freak me out.

[Michelle Deng]

Yeah. Yeah. In the US We. We hit a ton of deer with our cars. More than 2 million a year. Whoa. And that's just like, what's Reported. And most of the time when we hit them, it's. It's dark out, like at dawn or.

[Meryl Horne]

At dusk, because that's when the deer are, like, out and about.

[Michelle Deng]

Yeah. There's actually a word for when animals are on this kind of schedule. Here's Laura.

[Laura Prue]

It's one of my favorite terms. It's called crepuscular.

[Michelle Deng]

Crepuscular.

[Laura Prue]

I really like that. Crepuscular.

[Michelle Deng]

Yes.

[Meryl Horne]

That is a nice word. Crepuscular. I can't say crepuscular, and I think.

[Michelle Deng]

I'm still saying it wrong.

[Meryl Horne]

Okay. And that literally means that you're more active when it's dawn and dusk.

[Michelle Deng]

Yes. And so, like, these are the times when it's darker out, it's harder to see them. And those accidents can be really bad. Not just the deer, but the people involved, too. Like, every year in those accidents, almost 60,000 people get hurt and more than 400 people die. Wow. You know, fun fact. Maybe not a nice fact, but this is the mammal in the US that's responsible for the most human deaths.

[Meryl Horne]

What is deer? Yeah, that's a fun fact. I'm sorry. So it's actually a really big problem. It's like, if there was a. Another animal that was killing that many humans, we would be, like, up in arms about this.

[Michelle Deng]

And so to connect this back to daylight saving time, when it gets darker earlier, that means a lot of us are commuting when it's darker as well. And in the fall, there's this other thing that's happening for the deer. They are actually busy getting it on.

[Jamie Zeitzer]

Oh.

[Laura Prue]

So the rut is their mating season, and they are just jacked up on hormones. The males, the bucks are just running around looking for females, and they're not paying as much attention. They're moving a lot more.

[Michelle Deng]

Oh, no.

[Meryl Horne]

So they're, like, even more active when the change is happening.

[Michelle Deng]

Yeah. Laura said that some studies find that deer are moving up to 50% more this time of year. And Laura was like, with all that going on and adding the fact that it's getting darker earlier, is that causing us to hit more deer? So she and her team decided to look into this, and they started scraping national and state databases on car collision reports.

[Laura Prue]

So we ended up collecting records of over a million deer vehicle collisions across 23 states.

[Michelle Deng]

Laura and her team wanted to know, like, the time, the date, and the location of these accidents to see how the number of collisions change the week after daylight saving time ends. Okay, so here's Laura.

[Laura Prue]

Suddenly now, the evening rush hour. Is more in the dark when it's much harder for us to see the deer. And that really causes the collision rates to spike. What we found was that that switch in the fall led to a 16% increase in collisions. Just comparing the week before the switch to the week after.

[Michelle Deng]

Oof.

[Meryl Horne]

Okay, well, so there's one reason that we shouldn't be doing this. Cause that means, theoretically, then, more people are also dying if there's more accidents overall.

[Michelle Deng]

Yeah. Laura and her team were thinking. They were like, what would happen if we just got rid of the switch? Yeah. What if we did daylight saving time all year round so we had more light in the evening all year round? Like, how many more deer collisions would that prevent? So they did a bunch of math on that and estimated that having permanent daylight saving time could prevent over 36,000 deer car accidents a year across the U.S. whoa. And she calculated that would mean 2,000 fewer injuries and 33 fewer deaths.

[Commercial Announcer]

What?

[Laura Prue]

Yeah, I was surprised because, yeah, I thought it would just be a kind of a maybe a little blip. But we. Yeah, we found it was a pretty substantial effect.

[Meryl Horne]

That's huge. That's like. I mean, for those people, that would make. Obviously make a huge difference. That's pretty strong evidence. I feel like we should just keep daylight savings time.

[Michelle Deng]

They also found that if we had permanent daylight saving time, that it would save us $1.2 billion from those accidents. But total cost of medical bills and repairs. And it's not just about the deer here in the US in case you were wondering, the same thing is true in Australia for koalas. Oh, no.

[Meryl Horne]

The koalas get hit by cars.

[Michelle Deng]

There were some researchers from Queensland, Australia, that found that fewer koalas would get whacked if they went to permanent daylight saving time. Wow. Okay.

[Meryl Horne]

Though, I mean, I hate to sound like this. I'm skeptical that, like, hitting a koala would kill as many people as hitting a deer. Sad to think about, but it seems like they just kind of squish under your car.

[Michelle Deng]

Oh, yeah, I know. And another big argument is that less crime happens when it's lighter out in the evening. Like, there was one study that found that in the US Robberies decreased during daylight saving time in the evening hours. Robberies went down by 27% when you compare daylight saving time to standard time.

[Meryl Horne]

Oh, that makes sense. Yeah.

[Michelle Deng]

Bottom line for Laura, though, is that we should just really get rid of the switch. And she's a proponent for moving to permanent daylight saving time all year round.

[Laura Prue]

Like, there's just. In my opinion. A lot more cost to switching human lives and thousands of injuries.

[Michelle Deng]

Okay, so that's some of the big players in Team Daylight Saving Time all the time. Less accidents with deer and less crime. What do you think overall? Are you currently convinced that we should stay on Daylight Saving Time all year?

[Meryl Horne]

I feel like we should. That's what I would pick. I'm more of a night person than a morning person. I'd rather have the sunlight after work. And I hate that switching itself is such a pain. I don't see why we don't just do it all year round now. Let's do it.

[Michelle Deng]

I've only told you part of the science here. There's a whole other field of scientists that say we should have standard time all year instead.

[Meryl Horne]

What?

[Laura Prue]

Why?

[Meryl Horne]

Why would anybody want the darkness all year round?

[Michelle Deng]

We're going to get into that after the break.

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[Michelle Deng]

So good. So good. So good.

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[Michelle Deng]

Hey hey hey hey.

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[Michelle Deng]

Welcome back. I'm Michelle Deng. And today we're telling you about the effects of changing our clocks twice a year here with Meryl Horne. So let's talk about another piece of this debate. The idea that switches are bad for our health and that we should be on permanent standard time. This is the argument you hear a lot from people who study sleep. So this big idea that switches are bad for our sleep particularly has to do with that spring switch when we spring forward. Because a lot of us lose an hour of sleep.

[Meryl Horne]

Yeah.

[Michelle Deng]

And sleep sciences say like that not only messes with you cognitively, but also can increase the risk of, like, heart attacks and strokes. Oh, really? Yeah, you can hear this kind of thing all the time on the news. We'll lose an extra hour of sleep as we spring forward tomorrow. Research shows the bad news doesn't stop there. The risk for heart attack and stroke goes up in the first two days. The time change can cause an increase in heart attacks, strokes, car accidents, exhaustion and depression.

[Jamie Zeitzer]

One hour. One hour is all it takes.

[Michelle Deng]

That's insane.

[Jamie Zeitzer]

That's how fragile and vulnerable your body is to even just the smallest perturbation of sleep.

[Michelle Deng]

And the idea here is that some of this stuff might happen because you lose that hour of sleep and are more tired. But another worry is that daylight saving time goes on to screw with our circadian rhythm. And it's because of light. So in the morning, when the sun comes up and shines into your eyeballs, it sort of ends up screaming at the cells in your body to wake up. It gets us alert. It pumps out hormones to get us going through the day. And the timing of all this really matters. I talked about this with Jamie Zeitzer. He's a sleep scientist from Stanford University.

[Jamie Zeitzer]

And that bright sunshine closer to when you wake up is in theory going to strengthen your circadian clock. And this is the clock in your brain that basically helps to synchronize all of your internal organs and all of your functioning to this 24 hour solar cycle that we exist in. So you've got all these other clocks in organs. Right. You've got a clock in your liver, you've got a clock in your lungs, in your immune cells. Whoa.

[Meryl Horne]

So the sunlight is sort of waking up all these cells inside your body.

[Michelle Deng]

Yeah. I mean, most importantly, it's syncing up all these different systems in your body. And sunlight is the best source of, like, bright light that we can get for this kind of thing. Oh.

[Meryl Horne]

And so, like the. So the lights that we have in our houses, they're not strong enough to, like, synchronize everything together.

[Michelle Deng]

Yeah. And Jamie told me that, like, a really well lit bathroom or kitchen is going to be about 500 lux. Now, if you go outside, it's a nice day, bumps that up to 40,000. Whoa. And at noon, it's about 100,000.

[Meryl Horne]

The sun is so bright so that.

[Michelle Deng]

The sun just giving out so much more than what you're getting inside. Oh.

[Meryl Horne]

So maybe that's why I have a hard time waking up in the morning, is because I do not currently go outside for kick in the morning and expose myself.

[Michelle Deng]

And the thing is that bright light is helping to signal the central circadian clock in your brain.

[Jamie Zeitzer]

You can kind of think of it like a conductor of an orchestra.

[Michelle Deng]

And the cells and organs in your body are like sections of an orchestra. Like Jamie says, you've got the violins, the oboes, the flutes, and they need to be guided to start and stop their task at the right time.

[Jamie Zeitzer]

And that's basically what this central circadian clock is doing, is making sure everything. It's a strong conductor and making sure all the instruments are synchronized with each other so that you have a beautiful tune. And early morning light exposure helps it not only know what time it is, but also helps it be a stronger conductor for this orchestra.

[Michelle Deng]

Hmm. I'm assuming you know about that part of the brain, Meryl, being the brain person, the brain scientist.

[Meryl Horne]

The suprachmatic nucleus.

[Michelle Deng]

Yeah, you're right. That is the suprachiasmatic nuclei. Correct.

[Meryl Horne]

Hey, I still remember something from grad school.

[Michelle Deng]

It's like this little itty bit of the hypothalamus. Yeah. That the eyes talk to.

[Meryl Horne]

And that's like the conductor.

[Michelle Deng]

Yes, yes. Now, Jamie says when you mess with your sleep schedule and light, the messier the orchestra can get, like the weaker your circadian rhythm can get.

[Jamie Zeitzer]

Now, if you have an erratic sleep wake cycle, which really also translates to an erratic light dark cycle, then you get a weaker clock.

[Michelle Deng]

So let me give you an example. Imagine we are in the spring, okay. And daylight saving time is about to start. You are used to waking up at 6am for work. And the sunrise used to be at 6, but now rises at 7 an hour later.

[Meryl Horne]

Then you're.

[Michelle Deng]

You're still waking up at 6 for work, but now in the dark. And Jamie says that means you start poking the clock.

[Jamie Zeitzer]

Right. And every time you're poking the clock. And when you have a weaker clock, it's like having again this weak conductor and the organs don't work quite as well.

[Michelle Deng]

The organs stop talking to each other as well. And so they stop working together as well as if they were nicely synchronized. Like imagine if I started missing all your work slack messages. Uh huh.

[Meryl Horne]

Like even more than usual. You mean Michelle?

[Michelle Deng]

Yeah, I guess I could use some morning sunlight too.

[Meryl Horne]

Okay, but so wait, what, so what's going on with our organs?

[Michelle Deng]

Okay, yeah. So this is where when you have disruptive clock changes, it can start to affect your health. Because a circadian system does play a big role in almost all of your body's functions. Like Jamie said, one area we have pretty good evidence is that it affects your metabolism. So say for example, your body has this ability to figure out how many calories you need, but when your circadian.

[Jamie Zeitzer]

Clock is weaker, it's able to basically less accurately determine this. There is this connection between your metabolism and expectation of food when you're eating, how much you're expected to eat and the circadian clock. So the, the way that you can see this most easily is lots of data looking at individuals who do shift work. You see much higher rates of obesity in people who end up doing shift work.

[Meryl Horne]

But that's like an extreme situation. Like we're not all suddenly like waking up in the middle of the night and working a night shift. When that happens, it's only an hour and it's only twice a year. Like I'm still kind of skept there are negative consequences from just that one shift.

[Michelle Deng]

Well, it's not just the switch itself that messes with our circadian clock. Another argument they talk about is this idea that standard time is just better for us in general. Right. That it's better for our clocks because it matches our so called like natural states. Like if we were living in a forest or something, that it's kind of this like evolutionary argument that our bodies are built to wake up naturally with the sunlight, that you're waking as close.

[Meryl Horne]

To the sun as possible. That would happen more often if we stayed on standard time all year round.

[Michelle Deng]

Yes. Yeah. And they've also looked at societies of people who don't use artificial light, where they've studied their sleep cycle and they do wake up with the sun and wind down after that sun has gone down. And Jamie told me that because of.

[Jamie Zeitzer]

This there are a lot of people who are in the sleep and circadian fields who have been stomping their feet for years about how important it is to get rid of the switch and how critical it is to be in permanent standard time. And they have been very vocal about this.

[Michelle Deng]

And maybe it's not exactly foot stomping, but the American Academy of Sleep Medicine, the Sleep Research Society, the National Sleep foundation all say we should be on permanent standard time.

[Meryl Horne]

I guess, I mean, I can see why there's, like, a theory for why it would be important. I'm still not convinced yet that we have, like, cold, hard evidence that this really, really makes it that much of a difference.

[Michelle Deng]

Actually, Meryl, Jamie felt the same way. I asked him about this. Were you stomping your feet with them?

[Jamie Zeitzer]

No.

[Meryl Horne]

What?

[Michelle Deng]

Yes.

[Meryl Horne]

So he's not one of them.

[Michelle Deng]

Jamie's got some gripes with the it's more natural argument. And he says that a lot of sleep scientists were kind of just shouting about this, like, theory.

[Jamie Zeitzer]

That's what everyone's been saying. Oh, according to the theory. Well, how about some data? This is what I've been saying for years is I'd like to see some data. And no one ever shows any data.

[Meryl Horne]

Yes, exactly. Me too. Where's the evidence?

[Michelle Deng]

Yeah. So Jamie went and got some. To see how big this impact actually is. Him and one of his grad students pulled together data on sunlight from all the counties across the contiguous US like when the sun rises and sets over a year. And then they basically wanted to see how much each mode of time pushes on the body's internal clock. So they took those times and we.

[Jamie Zeitzer]

Put that into a model of the circadian clock and said, okay, we put it into the clock. Here's the burden that we are pushing onto the clock in these three different time policies.

[Michelle Deng]

And they based the model on kind of an idealized person who, like, has a 9 to 5, gets a well lit office, but also gets sunlight in the morning and is outside in the evening. Then they took the numbers and matched it up to health data from the CDC for all of those counties. They wanted to see, like, which mode of time was the worst for our health. All your standard time, all your daylight saving time, or the switches like we have now.

[Meryl Horne]

Okay, so this is to see, like, when your clock is kind of getting poked the most.

[Michelle Deng]

Yeah. And Jamie saw that our clocks got poked the most with the switches having to deal with adjusting the clock twice a year. And that that level of clock poking was linked to worse health.

[Jamie Zeitzer]

What you see is that as a whole, we do better without the biannual shift. We found that for two very specific things. We found it for obesity rates and strokes.

[Michelle Deng]

Wow. Yeah. So those were the two, like, out of like chronic conditions that they looked at from the CDC data. Those are the two that stuck out and were significant.

[Meryl Horne]

So if we didn't have those switches, we would see. We would actually see lower obesity rates and fewer strokes.

[Michelle Deng]

That's what their model estimates, looking at just the effects of what's going on with our circadian rhythms. And so we talked about before the metabolism mechanism that would have to do with obesity rates. They're not quite sure on the mechanism for strokes, but when you have a messed up circadian rhythm, it does affect things like your blood pressure, blood clotting, and inflammation in your body. So those things might have to do with why a stroke could happen.

[Meryl Horne]

So the switches. This is saying the switches are bad.

[Michelle Deng]

Yes, the switches suck. And actually what Jamie found was that both permanent Daylight Saving time and Permanent Standard time would be better than the switches. Huh. But between those two, there was a winner. The best one was Drumroll Standard Time. No. Yeah. Looking at obesity and stroke Standard time was the best. They found that if we stopped switching and stayed in permanent standard time and, you know, did a good job of getting exposed to light, we could potentially prevent obesity in over 2 million people. What? And prevent strokes in 300,000 people.

[Jamie Zeitzer]

What?

[Michelle Deng]

Now? His study showed you could still avoid a bunch of cases of obesity and stroke if you had permanent Daylight saving time all year. But not as many Standard time still beat it out.

[Meryl Horne]

Oh, man. So is he one of the foot stompers now?

[Michelle Deng]

I was curious about that too. I mean, he was surprised.

[Jamie Zeitzer]

I went in very skeptical thinking, like, ah, we're not gonna find anything and couldn't disprove it. We kept on showing that this was real. Um, and so that kind of, you know, that kind of convinced me that there's something there.

[Michelle Deng]

So Jamie's not a foot stomping kind of guy now, but he did come away acknowledging that there's some data here for Team Standard Time. And by the way, Jamie's study didn't find an association with heart attacks in either of these long term scenarios. There is a link you see in some earlier studies where more heart attacks occurred the week after losing that hour of sleep in the spring switch. But the effect size is pretty small. And another big study just came out that didn't see a link at all to the switch.

[Meryl Horne]

Okay, so, but big picture here. What should we do then? Like, which side is the science pointing to?

[Michelle Deng]

Yeah, it's kind of funny. I thought there'd be a clearer answer here, but it's messier than I thought.

[Meryl Horne]

Feels like we're stuck in limbo or something because everyone agrees that the changes themselves are bad, but we just now can't decide on what we should stay in. Is that right?

[Michelle Deng]

Yeah. And the US public is pretty mixed on all this too. A couple of polls from earlier this year found different things. Like, one found that about half of people want to keep standard time all year round, but another found that half of the people want to keep daylight saving time all year round.

[Meryl Horne]

Okay, so not that helpful then. Cause like, even if we got rid of it, which one would we go for?

[Michelle Deng]

Meryl, if you were science advisor here, what do you think you'd do?

[Meryl Horne]

Okay, I think I have a solution. Can we just like split down the middle? Like, what if we instead of picking an hour earlier or an hour later, if we did like 30 minutes. Is that possible?

[Michelle Deng]

Yeah, some scientists have actually brought this idea up too. But Meryl, could you imagine the logistics of being a half hour offset from other countries could be kind of a headache. But places like India and parts of Australia have made it work, so.

[Meryl Horne]

So what would you do, Michelle?

[Michelle Deng]

Yeah, honestly, I struggle with making a call because in real life there's just so much variation in people's schedules. Like in Jamie's study, the model was based on sort of this ideal person with an ideal light exposure. And a lot of us don't get that. So maybe the benefits of sticking on standard time would be smaller than what he found. And then when it comes to considering permanent Daylight saving time, where you live matters a lot too. Like, if you live on the western edge of your time zone, places like Indianapolis, Salt Lake City, Seattle, you could be looking at like 9am Sunrises in the winter, which that would kind of suck too. It's pretty late. Okay.

[Meryl Horne]

Yeah, yeah, but you gotta pick a side. Like it sucks now with the switches. There's gotta be. Something's gotta be the best.

[Michelle Deng]

So, Meryl, I think controversial take, but I think we should stick with what we have now until the science is super clear.

[Meryl Horne]

Even though we know the switches themselves are really bad?

[Michelle Deng]

Yeah, just. Cause I don't think. I don't think we actually know what the best option is yet. So I'm kind of holding out, huh?

[Meryl Horne]

So you really want to see definitive science so that when we do finally make this decision, we can be totally confident that it's going to make the most people happy? Is that what you're thinking?

[Michelle Deng]

Yeah, exactly. Yeah.

[Meryl Horne]

Okay, but then what are we supposed to do in the meantime? Like, now that we know that the switches are terrible?

[Michelle Deng]

Yeah. Well, if you're worried about this messing up your sleep or your body, There is something you can do to make the switches easier. Oh, and yeah, and that is to adjust your sleep time by 15 minutes a day the week before the actual switch. Okay. Basically ease into the switches so it's not a whiplash for your body.

[Meryl Horne]

So we, like in this case, start trying to go to bed 15 minutes early a few days beforehand so that when the actual time change happens, our bodies will just slide right into it and be like, oh, this is totally okay. Okay, I could try that. I guess it seems kind of annoying, to be honest, but.

[Michelle Deng]

But anyway, Meryl, you have a few days heads up. So get on it tonight. All right?

[Meryl Horne]

Homework.

[Michelle Deng]

All right.

[Meryl Horne]

Thanks, Michelle.

[Michelle Deng]

Thanks, Meryl. That's signs, verses. There were 58 citations in this episode. If you'd like to check them out, just head over to our show notes and click on the link to our transcript. This episode was produced by me, Michelle Dang, with help from Rose Rimler, Meryl Horn, Aketti Foster. Keys and Wendy Zuckerman were edited by Blythe Terrell. Our executive producer Producer is Wendy Zuckerman. Mix and sound design by Bobby Lord. Fact checking by Erica Akiko Howard. Music written by Peter Leonard, Bobby Lord so Wiley, Emma Munger and Bumi Hidaka. And a special thanks to researcher Dr. Isis Saponanete who also spoke to me for this episode. We'll fact you soon.

[Jamie Zeitzer]

And Doug, here we have the Limu emu in its natural habitat, helping people customize their car insurance and save hundreds with Liberty Mutual. Fascinating. It's accompanied by his natural ally, Doug.

[Michelle Deng]

Uh, limu is that guy with the binoculars watching us?

[Jamie Zeitzer]

Cut the camera. They see us. Only pay for what you [e-mail] Liberty Liberty Liberty. Liberty Savings Ferry Unwritten by Liberty Mutual Insurance Company and affiliates. Excludes Massachusetts.