daylight saving time

Daylight Saving Time May Be Killing Us — So Why Haven't We Abolished It?

Researchers have drawn a connection between heart attacks and daylight saving time for decades

This article was updated March 10, 2022.

Daylight saving time may be killing you. Yes, on its face, that may sound a bit dramatic. But there's an increasing number of researchers in the scientific community who say that just may be the case.

A growing body of research says that while many factors contribute to heart attacks, the high number of such attacks every March is aggravated further by one more factor: the clock. Specifically, the time shift can cause circadian disruption in humans, a condition linked to countless disorders and diseases.

“This is not hyperbolic, we literally have data on this,” says Dr. Kathryn Roecklein. “The rate of heart attacks is higher in the week or two after the time change.”

Why do we have daylight saving time in the first place?

Founding Father Benjamin Franklin gets too much credit for the origins of daylight saving time. New Zealand entomologist George Vernon Hudson proposed the time change in an 1895 paper (because he wanted more daylight hours to look at bugs, of course).

In the U.S., daylight saving time has been used inconsistently throughout history. It was first created during World War I as a way to save energy. Congress passed the Standard Time Act in 1918, drawing the boundaries between time zones and formally establishing daylight saving time.

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After the war, the decision to observe daylight saving time was left up to the states, but the practice again resurfaced as a federal law during World War II, again to conserve energy. According to the Department of Defense, time zones were nicknamed "war time" to reflect that the time change was part of the war effort. You might have heard "Pacific Standard Time" referred to as "Pacific War Time."

The point was this: with more of the common work and leisure hours taking place during daylight, there would be fewer hours inside with the lights on at night. Additionally, fewer people will need to turn the lights on if it's already daylight when they wake up in the morning.

Today, daylight saving time is left up to the states under the Uniform Time Act of 1966, though most states implement DST.

Who is in charge of daylight saving time in the U.S.?

The U.S. Department of Transportation oversees the implementation of daylight saving time and time zones.

The DOT says daylight saving time prevents traffic injuries since more people are traveling to school and work during daylight.

Transportation and time laws are linked out of necessity, according to the Arizona State Library. The spread of railroads led to the first effort toward standardized time, which was needed for the schedules to make sense across many parts of the country. Before that, what time it was might depend on what community you were in.

These states and territories don't have daylight saving time

Hawaii, most of Arizona and American Samoa, Guam, Puerto Rico and the Virgin Islands don't observe daylight saving time.

Hawaii has actually never observed daylight saving time. Unlike the continental United States, Hawaii is near the equator, so the sunrise and sunset times stay pretty consistent throughout the year.

Most of Arizona does not observe daylight saving time, but the Navajo Nation does. According to timeanddate.com, Arizonans largely prefer to run errands and go out during the evening due to intense heat during the day.

Since 2019, 32 states have discussed legislation about daylight saving time. Most of these are efforts are to convince the federal government to end DST and allow states to set their own time, which could either be permanent standard time or permanent DST.

Why experts say daylight saving time might be killing us

Roecklein’s Psychology Lab at the University of Pittsburgh researches circadian rhythms, what most of us call our internal clocks. Circadian rhythms form a timing mechanism regulated at the DNA level — in the nucleus of every cell.

This means two things: one, every cell is potentially its own clock, and two, these clocks regulate physiological functions in our bodies. Body temperature, blood pressure, glucose, cortisol, melatonin, testosterone — they’re all regulated by these clocks. And these clocks form a network that connects behind your optic nerve in a place called the SCN. When the optic nerve senses light, it communicates that to your network of cellular clocks.

“We've kind of disrupted the natural environment, because we have created all this artificial light,” says Roecklein. “What are the consequences of that to human health? And can we reverse some of the ‘unintended’ consequences of industrialization?"

Researchers have recognized a connection between heart attacks and daylight saving time for decades. Historically, the blame was placed on inconsistent sleeping patterns due to the time shift and the fact that nobody likes Mondays.

Daylight saving time can disrupt your circadian rhythm, and your health

Today, chronobiologists like Dr. Emily Manoogian at The Salk Institute can explain what our circadian network is doing behind the scenes, and why it can drive up heart attack rates in March.

“It's coordinating melatonin to help keep you drowsy, also keep your insulin from being secreted so you don’t eat at night, and it also helps you wake up by inducing a peak of cortisol right before you wake up — to wake you up. When that can be mistimed, that's also a big problem because if you're already awake and then you get this peak in cortisol, it doesn't just change the cortisol event, it changes other aspects of your heart functioning,” she says.

“If you're constantly living on that schedule your body can probably adjust a little bit, but constantly having to wake up when it's dark, and constantly having to go to bed when it's light is going to just compromise the system,” Manoogian added.

“Circadian disruption is linked to any chronic disease you could think of. In fact, shift work is a common cause of circadian disruption. Shift work is also known as a carcinogen by the World Health Organization, because it does so much damage there. But cancer, cardiovascular disease, metabolic disease, every affective disorder, bipolar, major depression, they're all linked to circadian disruption.”

Experts say eliminating daylight saving time could prevent chronic diseases

She says this is one reason scientists are pushing to abolish daylight saving time. This has already happened in the European Union, where DST originated.

Roecklein says the U.S. should stick to standard time to alleviate the disease impacts of daylight saving time.

“If you could do one thing that improved our nationwide or worldwide obesity epidemic, the rates of chronic metabolic diseases like cardiovascular disease and diabetes, that lengthened people's lifespan, that reduces the risk of depression, and substance use and ADHD, and sleep disorders like insomnia," says Roecklein.

"If you could increase GDP. If you can increase people's productivity, their sense of well-being and their sense of alertness... If you could do one thing to accomplish all of those effects it would be to just stop having daylight saving time," she adds. "Just adopt standard time permanently."