It's time to 'spring forward.' Here's how daylight saving time can affect your health.

Woman looking at her phone
Daylight saving time starts this Sunday. Here's how changing the clocks can affect your body and brain. (Getty Images)

Daylight saving time begins at 2 a.m. on Sunday, March 10, when we set the clocks forward and lose one hour of sleep. And while the centuries-old practice allows us to enjoy more daylight hours — at least until Nov. 3, when we "fall back" — it may mess with our well-being.

Why is "springing forward" so impactful? "Most people don't have an hour to spare," Dr. Rafael Pelayo, clinical professor of the Sleep Medicine Division at Stanford University's School of Medicine, tells Yahoo Life. "America is sleep-deprived to begin with, so losing that hour disrupts the length and quality of rest."

Waking up an hour earlier than we're used to can interfere with our circadian rhythm, or natural 24-hour body clock, and make us feel sleepier and more disoriented, which in turn can result in other health consequences. Here's what to know.

You may not sleep as well

We’ll all lose an hour of sleep when the clocks spring forward on Sunday — assuming we don’t go to bed earlier than usual — but, for some, the sleep disruptions linger. Nearly 14% of people said they “slept poorly” during the two weeks following daylight saving time in March 2021, compared to just 1.7% prior to the shift, according to a 2022 study published in the journal Sleep Science and Practice. After the clocks changed, study participants were 18% less likely to say they were “well rested” in the morning.

Teens may be hit especially hard. High school students lost an average of 32 minutes of sleep each night for the week following the switch to daylight saving time, according to a 2015 study published in the Journal of Clinical Sleep Medicine. As a result, teens were less attentive, slower to react and generally felt more sleepy. We all rely on daylight and nightfall to signal to our bodies when it’s time to wake up and go to sleep, so even subtle changes can throw off the circadian rhythms that govern our rest and wakefulness. But teens are especially susceptible, according to the study authors, because they start school early and have a tendency to stay up late.

Driving becomes more dangerous

A January 2020 Current Biology study of 732,835 U.S. accidents from 1996 to 2017 found that fatal car accidents increased by 6% (the equivalent of 28 additional deaths per year) during the week of the time change, due to fatigue and driving in the dark.

The study found that the farther west a person lives, the likelier they are to be involved in a deadly crash because those in western regions see the latest sunrise time during daylight saving time, likely leading to greater disruption of their circadian rhythms, compared to those further east.

Study author Celine Vetter told ScienceDaily, "Our study provides additional, rigorous evidence that the switch to daylight saving time in spring leads to negative health and safety impacts. These effects on fatal traffic accidents are real, and these deaths can be prevented."

You might be distracted at work

Watch your internet habits on the Monday after daylight saving time — that's when people spend more time on websites like Facebook, YouTube and, says a study published in the Journal of Applied Psychology. These entertainment-based inquiries — dubbed "cyberloafing" by researchers — had "considerably" higher search volume on the Mondays after the time change. "One limitation is that we don't know for sure whether people were at work or whether their entertainment searches were work-related," study author Chris Barnes, professor of management at the University of Washington, tells Yahoo Life.

A separate study conducted by Facebook in 2014 found a "significantly increased usage" of the word “tired” written in posts the week of the time change, along with spikes in the words "sleepy" and "exhausted."

Workplace injuries are more common

Losing that hour can be dangerous if you work in a job that requires physical labor, found a 2009 study from the Journal of Applied Psychology. Barnes, who authored the study, examined half a million injuries among mineworkers over a period of five years and concluded that on the Monday after daylight saving time — "Sleepy Monday" — injuries increase by more than 5% and are more severe. "The ability to control intention, make decisions and focus on tasks suffers that day because sleep deprivation affects the brain’s prefrontal cortex," Barnes tells Yahoo Life. But in the fall, when the clocks are set back, there are no major differences in the number or degree of injuries.

Your risk of heart attack or stroke may rise (a little)

Not getting enough sleep can indirectly affect your risk of heart attack, stroke and other cardiovascular problems by triggering an increase in hormones, like cortisol, that put stress on the heart. But springing forward an hour may not be the menace might have thought, according to new research published in Mayo Clinic Proceedings: Innovations, Quality & Outcome.

Previous research suggested there could be as much as a 24% increase in the number of heart attacks on the Monday after the clocks change, according to a study published in the BMJ journal Open Heart, compared to a 21% reduction on the following day, Tuesday. But the new study found that rates of heart attacks and other cardiovascular problems rise by 3% the Monday after daylight saving time, and 4% on the following Friday, based on five (pre-pandemic) years' worth of hospital data from across the U.S. That increase isn’t enough to suggest that changing the clocks is leading to a surge in heart attacks, considering that hospitals might see similar fluctuations in the number of heart attacks on a day-to-day basis, study author and Mayo Clinic cardiology fellow Dr. Benjamin Satterfield tells Yahoo Life. While there was a small rise in cardiovascular hospitalizations after daylight saving time took effect, “it wasn’t anything we need to worry about from a clinical standpoint," he says.

Another earlier piece of research found a 10% increase in heart attacks on the Monday and Tuesday following the time change; that risk declined by 10% in November. Study author Martin E. Young of the Division of Cardiovascular Diseases at the University of Alabama, Birmingham, said in a press release, “Exactly why this happens is not known but there are several theories. Sleep deprivation, the body’s circadian clock and immune responses all can come into play when considering reasons that changing the time by an hour can be detrimental to someone's health."

While Satterfield’s study suggests daylight saving time is unlikely to drastically affect heart attack risk, he acknowledges there are some limitations to the study, and says the American Heart Association’s recommendations about springing forward are good advice to follow:

  • Get outside and get as much sunshine as you can each day. This can help adjust your body rhythm for the change to come.

  • Start winding down earlier. You can’t make up for lost sleep, but you can get ahead of a sleep deficit.

  • Don’t compensate with extra caffeine. Too much coffee, tea or soda can put further stress on your heart and cardiovascular system.

You might miss a doctor's appointment

People are significantly more likely to miss their scheduled doctor's visit during the week of daylight saving time in March, found a study of more than two million medical appointments published in The Journal of Biological and Medical Rhythm Research. The reverse was true when transitioning out of daylight saving time in November. Researchers guessed that disrupted sleep patterns could throw people off but acknowledged that reasons for non-attendance weren't known.

Some good news

All that said, for the states that participate (Hawaii and most of Arizona opt out) there are advantages to changing the clock in March: People can enjoy more outdoor activities, for example, and there is a 2.9% reduction in criminal assault on the subsequent Monday (lethargy doesn't motivate criminals, said the researcher), while robbery rates for the day fall by 7%.

How to prepare

According to the National Sleep Foundation, you can ease into the transition by going to bed about 20 minutes earlier each night leading up to the change, and trying to sleep in an extra 30 minutes on the first morning of the time change.

This story was originally published on March 6, 2020 and has been updated.