Published: Oct. 17, 2019


Welcome to Brainwaves, a podcast about big ideas, produced at the University of Colorado Boulder.

I’m Paul Beique.

This week…

(Clock ticking)

We “fall back” to standard time pretty soon, the first weekend of November.

But time might be up for daylight saving time.

In 2019 -- at least 36 states have introduced legislation to stop changing time every spring and fall. 

And science shows the time switch might not just be bad for your health, it could actually kill you.

Despite all of that, there are some outstanding questions and concerns about doing away with the semi-annual switch.

So, let’s do the time warp again. 

We’ll start by taking a look at the most obvious issue.

When you set your clocks ahead an hour each spring, you lose an hour of sleep.

More than inconvenient, Brainwaves’ Dirk Martin found out it can be pretty bad for you.

Before bedtime on November 2, about 1.2 billion people around the world will turn their clocks back one hour, adding a little more light to their mornings and bringing darkness on a little earlier.

As tough as those first dark evenings may seem, some scientists say they’re actually good for you. So good, they’d like to stick to standard time — which we’re switching to now — year-round.
My name is Celine Vetter, I am an assistant professor of integrative physiology here at CU Boulder.

Vetter is also chair of public outreach for the society for research on biological rhythms, an international group of scientists calling for the end to daylight saving time.
They argue that when countries first started switching clocks back and forth a century ago to save electricity at night, they didn’t realize how closely human health is tied to the movement of the sun.
This whole conversation is going on right now because there is accumulating evidence that DST, one, does not have the beneficial effects on the energy levels that we consume, and second, there has been some observational data suggesting that there are actually adverse effects on human health and safety.
As Vetter explains it, our body has its own circadian clock — a roughly 24-hour cycle governing when hormones are released, what our body temperature is, and when we get hungry, tired and feel like waking up.

 light plays a key role in keeping this clock ticking on time. The minute we pull open the blinds and those rays hit our eye, it kick-starts biological processes that help wake us up.
Less light signals the body to wind down for sleep.
When you move the clocks in spring to an hour later, what happens is that your mornings get darker and your evening gets brighter. Now, what happens on our human behavioral and physiological level is that this change in the light/dark cycle will push the majority of the population to a later phase. You will actually have even more difficulties getting up in the morning because the light in the evening actually makes you later - it makes it even harder for people to wake up by themselves at times that are compatible with daytime work.
The problems don’t end there. Some research suggests that when our social-clock is chronically out of sync with our biological clock, bad things happen. 
It’s known as social jet lag.

DST is one kind of social jet lag. We know it increases your risk of being obese or overweight, and this has been replicated in many studies. There has been evidence that social jet lag is associated with impaired glucose metabolism and type 2 diabetes risk.

As states have begun to introduce legislation to implement permanent daylight saving time, Vetter and sleep specialists like her have grown concerned.
Yeah, so I think there are two questions: Should we abolish that switching back and forth, and then do we stick to standard time or Daylight Savings Time if we get rid of the switching? We think that there is enough evidence that the switching is not good for us and we should get rid of it, and as chrono biologists we favor standard time.

Vetter notes that the farther west you live in a time zone, the later the sun rises. 
If daylight saving time were to become year-round, some areas of the united states wouldn’t see daylight until 10 a.m. at certain times of the winter.

Think about your kids at a bus stop in the morning, and it is already hard in the winter-time. We think it would just get worse.
Advocates of permanent daylight saving time are quick to mention that it would give us longer evenings so we can get out and exercise and enjoy our summer nights.
Under year-round standard time those summer nights would get a little shorter. 
But Vetter believes the payoff, in terms of health and sleep, would be worth it.
It will get darker early, but we shouldn’t forget that the evening time is the time where we shouldn’t be exposed to that much light if we want to be entrained to a daytime cycle. I know that there are a lot of discussions about we love to sit outside in the summer, and it’s nice and that it’s so light and social. The issue really is you can still be social. Your summers will still be beautiful even if it gets darker an hour earlier.


Aside from grogginess, daylight saving time could be killing people.

Brainwaves’ Andrew Sorensen talked to Austin Smith.

Smith is an economist at Miami University in Ohio, but we wanted to talk with him about research he did for his PhD at CU Boulder.

Smith found a couple of ways that daylight saving time, could be deadly.

What did you find with your research, what exactly were you looking at in terms of daylight saving time?

I was looking at the impact on fatal automobile crashes, and there were two possible mechansims through which you might expect an effect. You might think there would be a short-run effect, due to these transitions. When you jump from 2 a.m. to 3 a.m., you lose an hour in the middle of the night, and other studies had shown, that Americans at least, we don’t adapt to that by going to bed earlier or sleeping longer. We actually sleep less right at this—right at transition. 

So there’s about a 6% increase in fatal vehicle crashes immediately following that fall transiton. And you see that taper off, after the first week it’s down to a 3 to 4% increase. After the second week, there’s no statistically significant increase. So, it lasts, kind of, one to two weeks after that transition.

So, I did find a spike in crashes that occur right after the spring transition. 

The other way you might expect is through what hours of the day are light. So having more ambient light can help reduce crash risks, just because you can see better as a driver. And so you actually do see an increase in fatal car accidents occurring in the morning hours that have become darker due to daylight saving time, but that is offset by a reduction in crashes in the evening, which is now lighter.

So, I found that we were reallocating when crashes occur in the day, but there was no net effect of changing when this ambient light occurs. 

And you found some, at least, through your research, some other research out there about other negative economic financial impacts. Can you tell us about those?

Yeah, so there’s a lot of research that finds the transitions are costly. That switching into daylight saving time, especially, because you lose that hour. Some of this research has documented an increase in workplace injuries, presumably due to fatigue, grogginess, or kind of being off your normal schedule. 

There’s also been some evidence of financial traders doing worse in the stock market in the days immediately following daylight saving time. And also increases in heart attacks.

I know when we originally reached out, you were scheduled to testify in front of Ohio legislators about all of this. What was their reception?

So Ohio is looking at eliminating these transitions. A lot of states are talking about whether it makes sense to continue to practice daylight saving time, because of evidence of these costs and the lack of a benefit in terms of energy savings.

Ohio’s specific proposal was to move to permanent daylight saving time. So, spring forward, but stop falling back, and kind of keep on that other time frame for the whole year.

So as part of my testimony, I gave them some analysis like we’ve talked about, some of the costs, some of the benefits. And one thing that’s important for states to consider in making this decision is what the current sunrise and sunset times are in a state.

So a state’s kind of position within a time zone really matters here. Some states have really early sunrises. Some have really late. So if you’re really east in a time zone, you have the earlier sunrise times. If you’re west in the time zone, you have later. 

So based on where Ohio is, we’re kind of on the western portion of the eastern time zone, so we have later sunrise times and later sunset times than a lot of other states. 

So for here, it might be more important to have ambient light remain in the morning, because we don’t have as much. 

And other states, it might make more sense to have ambient light in the evening, because they have less ambient light in the evening if you’re in the eastern portion of a time zone.  

So one of my key points in testifying was to try and explain what’s the right policy for one state, might not be the right policy for another state, just depending on their geography, where their location is relative to time zone boundaries. 

Anything else that you want to add that you think is kind of important to the conversation here?

I’d say there’s always new studies and new information coming out. So, researchers have really dedicated more time to this issue lately as more evidence came that we weren’t getting benefits from energy savings. This is a narrative that’s continuing to change, and kind of keeping—updating and being open to new evidence is really important.

Most of the states that want to end the daylight saving time switch probably won’t make any major changes soon.

Many of those state efforts require the federal government to take action first.

But we wanted to take a second to explore why people may not want to do away with time-hopping business as usual.

Brainwaves’ Cole Hemstreet has more.


We all do it twice a year, spring forward, fall back.

While there are plenty of people who wish we didn’t, there are some issues to sort out if we’re going to make changes.

As someone who has my summers off, I would be really upset at having shorter summer days, because I work all school year for those long summer days. So, yeah. I’d be against it.

Different groups have taken issue with various state bills to scrape the time switch.

Some people, like Chloe Dickson, a high school teacher, wouldn’t like the dark morning. 

I think it would be really hard for both students and people in charge of transportation to get kids to school safely if they were still going to school in the dark.

Bottom line, any change to the status quo here would impact a lot of people.

Not to mention that we might have to shift time zones as we know them, like we heard in that last piece.

On top of that, there are some industry groups that don’t like the idea of major daylight saving overhauls.

The ski industry helped scuttle a bill in Colorado. They basically told news reporters at the time that they like the clock *right* where it is, thank-you-very-much.

And anything else would be bad news for a $5 billion industry.

For Brainwaves, I’m Cole Hemstreet.

Thanks for listening to Brainwaves. I’m Paul Beique.

If you haven’t already, give us a follow wherever you get your podcasts. It really does make a big difference, and we appreciate it.

Today’s program was produced by Dirk Martin, Lisa Marshall, and Cole Hemstreet.

Andrew Sorensen is our executive producer. Sam Linnerooth is our digital producer.

Catch you next time, on Brainwaves.