At 2 A.M. on Sunday, most of the U.S. will set the clocks back by an hour. With the switch to standard time, we’ll get earlier sunshine and darker evenings—and an extra hour of sleep.
Research suggests standard time better aligns with our circadian rhythm, or internal clock, and reduces the risk of health complications. But changing to standard time comes with some risks, too, experts say.
Between “falling back” to standard time in November and “springing forward” to daylight saving time (DST) in March, experts say the switch to DST is the bigger disruption. In the days after the March time change, scientists have measured higher rates of lost sleep and an uptick in heart attacks. After the time change in November, however, those risks are lower.
On supporting science journalism
If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
Some research suggests rates of stroke go up around both spring and fall clock changes, although the risk of death is higher in the spring, says Beth Malow, a professor of neurology and pediatrics at Vanderbilt University.
On standard time, early risers get the benefit of a little more morning sunlight. Morning light is “one of the strongest forces” that aligns our bodies’ circadian rhythm with the outside world, Malow says. That alignment helps us wake up in the morning and drift off at night more easily.
After the fall time change, you might wake up well after the sun comes up—but that poses less of a risk than cutting off your body’s internal clock early, says Jamie Zeitzer, a professor and a sleep scientist at Stanford University. “You’re basically sleeping in,” he adds.
In fact, given the overall benefits of standard time, top medical organizations, including the American Medical Association, Sleep Research Society and American Academy of Sleep Medicine have fought efforts to make DST permanent—a frequent hobbyhorse in Congress.
A major downside to standard time, however, is less time spent outdoors. Some studies also suggest moving commuting times nearer to dusk in the fall increases the risk of vehicle collisions with deer and other wildlife, which are more active around sunset.
There are certain steps you can take to ensure a more smooth transition, experts say.
Number one, don’t go into a clock change while sleep-deprived, Malow says. And try to get as much exposure to morning light as possible throughout the season. (If you’re able to access one, a light box can be helpful for this on dark mornings in the spring.) Stay alert during dark commutes, when visibility may be limited, whether they’re on a spring morning or a fall evening, Malow adds. And if you’re consistently struggling with sleep, consider seeing a doctor.
In the fall, you may need to take extra care to get regular evening exercise in. And if you, like many Americans, aren’t getting enough shut-eye on most nights, consider using the clock change to set a new sleep habit, Malow says.
If your usual bedtime is 11 P.M., for instance, try going to bed when you’re tired instead—after the time change, that will be when the clocks read about 10 P.M.—and try to stick to the new schedule. “Take advantage of the fact that your body’s now going to be ready to go to bed earlier,” she says.
If nothing else, relish “sleeping in,” Zeitzer says. “Enjoy the extra hour of sleep.”
Subscribe to Support Independent Journalism
Great science journalism requires human expertise, time, effort and creativity. And it costs money. That’s why I and the journalists here at Scientific American hope you’ll join our community.
When you subscribe, you are supporting staff and freelance journalists who are passionate about telling science stories that are true, important and compelling. Our editors and reporters are often experts in their fields, which means they understand the nuances of big discoveries and can untangle the breakthroughs from the hype. With a subscription, you are also supporting rigorous fact-checking to ensure the words we publish are precise and accurate. And you’re supporting original illustrations, graphics and photos that bring you closer to an advanced laboratory, an ice sheet in Antarctica or a space mission in orbit. You’re helping us craft other types of high-quality journalism as well: Our newsletters are carefully written, edited and curated by staffers you have or will come to know and love. Our Science Quickly podcast is based on original reporting, collaboration with editors and scientists and exacting production.
Subscriptions keep this engine running so we can continue to deliver thoughtful, rigorous and independent science journalism to you. In an era of viral misinformation, this work is crucial. If you value what we do, I hope you’ll consider joining us as a subscriber
