Daylight Saving Time: Should We End It?

Hi, I'm Michelle Dang, 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.

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. I hate daylight savings. I just would like to have a moment of silence for how much daylight savings f***s 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 U.S., hundreds of bills have been proposed to do the same.

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. 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, even dangerous.

That daylight saving time could even kill you. Did you know the number of heart attacks increased right after daylight saving changes? Having to wake up in the dark is not only uncomfortable, it's actually really bad for your health long term. So today, we're looking at the science 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 vs. Daylight Saving Time is coming up after the break. This episode is sponsored by Anthropic, the team behind Claude.

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Daylight saving time. Is it bad for us and should we get rid of it? I'll be discussing the science today with senior producer Meryl Horn. Hey Meryl. Hey Michelle. Are you ready for the fall switch? Not at all. I hate daylight savings time. What part do you hate? Mostly because I have...

To small kids, it's like you spend all this time trying to make their bedtimes go well and get them up for school at a certain time. And then it's like you suddenly remember, oh crap, 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.

You don't think you get that extra hour of sleep in the fall switch? No. So Meryl, why do you think we have daylight saving time in the first place? I mean, I've heard it's... Because of the farmers, something to do with the farmers. 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 it was back during the World War I years. Wait, so it's only been around since World War I? 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. Why would that save fuel? Like if you can extend the day and the sunlight, you can then save costs on working into the night. Oh. 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. Oh. And other studies find it doesn't save energy at all.

Once we realized that the fuel thing didn't make sense, why did we keep it? Is it just kind of tradition? 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. Oh, that kind of makes sense. Like stores are open later in the summer in my neighborhood. Yeah, and interestingly, 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 hours.

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. Yeah, yeah, yeah. Does it actually help the economy? So there's studies on this too, and it's also, it's mixed. whether it actually helps or not. Even though the business people think it helps, it's not that clear that it's that good overall for businesses. It could 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 U.S. about to fall back. So meet Laura Pru. She's a scientist at the University of Washington. And like you, she finds the fall switch pretty annoying. 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 workday, you leave work and oh my God, it's dark out already. 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 Archimedes' 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 U.S. 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.

Yeah, I feel like this is not going to end well for the deer. Have you ever had any run-ins with deer? No, but it's so scary. I know people who have and it... It's so dangerous for everybody if there's an accident with one. So it does freak me out. Yeah, yeah. In the U.S., we hit a ton of deer with our cars, more than two million a year. Whoa.

And that's just like what's reported. And most of the time when we hit them, it's dark out like at dawn or at dusk because that's when the deer are like... out and about. Yeah, there's actually a word for when animals are on this kind of schedule. Here's Laura. It's one of my favorite terms. It's called crepuscular. Crepuscular. I really like that. Kerpuscular, yes. That is a nice word. Kerpuscular. I can't say it. Kerpuscular. And I think I'm still saying it wrong.

Okay, and that literally means that you're more active when it's dawn and dusk? 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 U.S. that's responsible for the most human deaths. 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 another animal that was killing that many humans, we would be like up in arms about this. 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. 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. Oh, no. So they're like even more active when the change is happening.

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. So we ended up...

collecting records of over a million deer vehicle collisions across 23 states. Laura and her team wanted to know 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. 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. Oof. Okay. Well, so there's one reason that we shouldn't be doing this. Because that means theoretically that more people are also dying.

if there was more accidents overall. 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. What? 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. That's huge. That's like...

I mean, for those people that would obviously make a huge difference, that's pretty strong evidence, I feel like. We should just keep daylight savings time. 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 U.S.

In case you were wondering, the same thing is true in Australia for koalas. Oh no, the koalas get hit by cars. 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. 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. Oh, yeah, I know. And another big argument is that less crime happens when it's lighter out in the evening. There was one study that found that in the U.S., robberies decreased during daylight saving time. In the evening hours, robberies went down by 27% when you compare daylight saving time to standard time. Oh.

That makes sense, yeah. 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. Like, there's just, in my opinion, a lot more costs. to switching human lives and thousands of injuries. 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. Yeah. 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 the 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. 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. What? Why? Why would anybody want the darkness all year round? We're going to get into that after the break. This episode is brought to you by Marshalls, where you never have to compromise between quality and price. The buyers of Marshalls hustle hard, working to bring you great deals on brand name and designer pieces.

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Welcome back. I'm Michelle Dang and today we're telling you about the effects of changing our clocks twice a year here with Meryl Horn. 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. Yeah. Sleep scientists say that not only messes with you cognitively, but also can increase the risk of heart attacks and strokes. Whoa, 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. accidents, exhaustion, and depression. One hour. One hour is all it takes. That's how fragile and vulnerable your body is to even just the smallest perturbation of sleep.

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.

pumps out hormones to get us going for 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. 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, so the sunlight is sort of waking up all these cells inside your body? Yeah, I mean, most importantly, it's syncing up all these different systems in your body.

sunlight is the best source of like bright light that we can get for this kind of thing. Oh, and so like the, so the lights that we have in our houses, they're not strong enough to like synchronize everything together? 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. And at noon, it's about 100,000. The sun is so bright. So the sun is just giving out so much more than what you're getting inside. So maybe that's why I... have a hard time waking up in the morning. It's because I do not currently go outside first thing in the morning and expose myself. And the thing is that bright light is helping to signal the central circadian clock in your brain.

You can kind of think of it like a conductor of an orchestra. 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. And that's basically what this central circadian clock is doing. It's making sure everything is 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. I'm assuming you know about that part of the brain. Meryl being the brain person. The brain scientist. The super cosmetic nucleus.

Yeah, you're right. That is the suprachiasmatic nuclei. Hey, I still remember something from grad school. It's like this little itty bit of the hypothalamus. Yeah. That the eyes talk to. And that's like the conductor. 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. 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. 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 6 a.m. for work, and the sunrise used to be at 6, but now rises at 7 an hour later. Then you're still waking up at 6 for work.

but now in the dark. And Jamie says that means... You start poking the clock, 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. 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.

Like even more than usual, you mean, Michelle? Yeah, I guess I could use some morning sunlight too. Okay, but so wait, what? So what's going on with our organs? Okay, yeah. So this is where when you have disruptive clock changes, it can start to affect your health.

Because the 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 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 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.

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 skeptical that there are negative consequences from it. just that one shift. 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 to the sun as possible. That would happen more often if we stayed on standard time all year round. 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 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. 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. 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 makes it that much of a difference.

Actually, Meryl, Jamie felt the same way. I asked him about this. Were you stomping your feet with them? No. What? Yes. So he's not one of them. 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. 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.

Yes, exactly. Me too. Where's the evidence? 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 U.S., 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 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. And they base the model on kind of an idealized person who like has a nine to five, 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. Okay, so this is to see like when your clock is kind of getting poked the most.

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. What you see is that...

As a whole, we do better without the biannual shift. We found it for two very specific things. We found it for obesity rates and strokes. Wow. Yeah, so out of chronic conditions that they looked at from the CDC data, those are the two that stuck out and were significant. So if we didn't have those switches, we would actually see lower...

obesity rates and fewer strokes? 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. So the switches, this is saying the switches are bad. 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 strokes, 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 and over... 2 million people. What? And prevent strokes in 300,000 people. What? 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. Oh, man. So is he one of the foot stompers now? I was curious about that, too. I mean, he was surprised. I went in very skeptical, thinking like, oh, we're not going to find anything. couldn't disprove it. We kept on showing that this was real. And so that kind of convinced me that there's something there.

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's 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. Okay, so but big picture here, what should we do then? Like, which side is the science pointing to? Yeah, it's like kind of funny. Like, I thought there'd be a clearer answer here, but it's messier than I thought.

It feels like we're stuck in limbo or something because everyone agrees that the changes themselves are bad, but we just like now can't decide on what we should stay in. Is that right? 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 daily saving time all year round. Okay, so not that helpful then, because like even if we got rid of it, which one would we go for? Meryl, if you were science advisor here, what do you think you'd do? Okay, I think I have a solution. Can we just like split down the middle? Like what?

We, instead of picking an hour earlier or an hour later, we did like 30 minutes. Is that possible? 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. So what would you do, Michelle?

Yeah, I 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 9 a.m. sunrises in the winter, which that would kind of suck too. It's pretty late. Okay. Yeah. Yeah. But you got to pick a side. Like it sucks now with the switches. There's got to be, something's got to be the best.

So Meryl, I think controversial take, but I think we should stick with what we have now until the science is super clear. Even though we know the switches themselves are really bad. Yeah. I don't think we actually know what the best option is yet. So I'm kind of holding out. Huh. So you really want to see...

definitive science so that when we do finally like make this decision, we can be like totally confident that it's going to make the most people happy. Is that what you're thinking? Yeah, exactly. Yeah. Okay. But then what are we supposed to do in the meantime? Like now that we know that the switches are terrible. 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. So we, like in this case, start trying to go to bed 15 minutes earlier, 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 but anyway Meryl you have a few days heads up so get on it tonight all right homework

All right. Thanks, Michelle. Thanks, Meryl. That's Science Versus. 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 Brimler, Meryl Horn, Akedi Foster-Keys, and Wendy Zuckerman. We're edited by Blythe Terrell. Our executive 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 Sapananate, who also spoke to me for this episode. We'll fact you soon.