Wright is not alone. As daylight saving time ticked toward its yearly end, sleep experts across the country stepped out in favor of standard time.
Scientists have linked sleep loss, heart attacks and an increased risk of dying in the hospital after a stroke to the transition to daylight saving time, neurologist Beth Malow wrote in Sleep in September. She testified to that this year before a U.S. House of Representatives subcommittee.
“My overall message was that permanent standard time was a healthier choice,” says Malow, of Vanderbilt University Medical Center in Nashville.
Morning light wakes up the brain
For both Malow and Wright, some of the most compelling studies examine U.S. time zone borders. Living on the late sunset side of a border takes a toll on people’s health and sleep compared with those living on the early sunset side, scientists suggested in 2019. A similar study in 2018 also found an increased risk of liver cancer the farther west people lived within a time zone, where the sun rises and sets later in the day.
But the downsides of nighttime light are not always crystal clear. A November study, for example, suggested that year-round daylight saving time would reduce deer-vehicle collisions (SN: 11/2/22). But studies like these can be hard to interpret, Malow says. Other factors may come into play, like deer’s seasonal activity and changing roadway conditions. “The car-crash literature has been so mixed,” she says. “I’ve seen stuff come out on both sides.”
Dark mornings and light evenings mean people’s body clocks don’t line up with the sun. That mismatch can hamper sleep, making for drowsy drivers, which may factor into collisions, Malow says. In the evenings, if “there’s still light in the sky, it messes with our brains.”
The brains of teens and tweens are even more vulnerable, Malow says. When kids go through puberty, the brain waits an hour or two longer to release melatonin, the “hormone of darkness,” which tells the bodies of kids and adults alike that it’s time to go to sleep.
Bedtime can be tough for older kids because, physiologically, they’re just not as sleepy as they used to be. And as I’ve learned with my daughter, if you throw early school start times in the mix, rising and shining can be even harder.
“I have a middle schooler, too. It’s brutal,” says Lisa Meltzer, a pediatric sleep psychologist at National Jewish Health in Denver. Some U.S. school districts are making changes that might make mornings easier. This year, most high schools and middle schools in California debuted later start times. Five years ago, Meltzer’s school district embarked on a similar experiment. What they learned can teach us how older kids might fare if daylight saving time were to stay put year-round, Meltzer says.
In 2017, the Cherry Creek School District in suburban Denver flipped middle and high schools’ early start times with elementary schools’ later ones. The change didn’t much affect younger kids, who still started class well after sunrise, at 8 a.m., says Meltzer, who presented the science behind changing school start times to her school board. But older kids, who started school at 8:20 a.m. or 8:50 a.m., noticed a big difference. They slept more at night and tended to function better during the day, Meltzer’s team reported most recently in the February Sleep Medicine.
“The number one thing [high-schoolers] said was how much they liked going to school when it was light out,” she says.
And it wasn’t just the students. Their teachers, too, felt the benefits of later start times, Meltzer and colleagues report November 6 in the Journal of School Health.
Morning light is crucial for keeping people’s bodies on schedule, Meltzer says. With permanent daylight saving time, kids will not have the same eye-opening, brain-wakening, a.m. sunshine. “We need morning sunlight to keep our internal clocks on track,” she says. “I cannot emphasize this enough.”
The Senate’s plan for year-round daylight saving time has thankfully stalled, so the plan for everlasting shift toward evening light is still up for debate.
In the meantime, we continue to contend with the biological stress of the biannual time changes.
For those struggling with sleep after a time change or in general, see our integrative strategies for promoting better sleep and practice good sleep basics:
- Try to wake up at the same time every day
- Keep a consistent sleep schedule even on weekends
- Avoid afternoon naps.
- Avoid afternoon caffeine.
- Avoid eating before bed, especially carb-rich foods
- Practice progressive relaxation