To the relief of many Americans, the period of daylight saving time is finally coming to a close.
Sunday, people living in states that follow this practice will set their clocks back, gaining the hour of sleep they lost in the spring. For most of the U.S., daylight saving time starts at 2 a.m. on the second Sunday of March and ends on the same time on the first Sunday of November.
The Department of Transportation, which is in charge of daylight saving time, says the practice saves energy, prevents traffic accidents and reduces crime. Sleep experts say the health consequences of losing sleep from daylight saving outweigh its value.
“There’s really no reason we should continue to do this back and forth,” said Erin Flynn-Evans, a consultant to the American Academy of Sleep Medicine’s Public Safety Committee. “The negative health consequences and the negative effect on multivehicular crashes in the spring are just not worth it.”
In a 2020 position statement, American Academy of Sleep Medicine said the U.S. should eliminate daylight saving time in favor of a year-round standard time. Here’s why most health experts agree:
Why is sleep so important?
Like diet and exercise, health experts say, sleep is essential for a healthy lifestyle.
“It’s one of the pillars of good health,” said Dr. Bhanu Kolla, associate professor of psychiatry and a consultant for the center for sleep medicine at the Mayo Clinic.
Sleep has been shown to improve cognitive functions like learning, problem-solving skills, decision-making and creativity. Insufficient sleep causes inattention, poor focusing and inability to monitor behavior, said Judith Owens, co-director of the pediatric sleep program at Boston Children’s Hospital and professor at Harvard Medical School.
“Individuals who don’t get enough sleep are more likely to take risks because they perceive less consequence,” she said. “For example, a child in elementary school darts out into the road because they are more impulsive and less vigilant.”
Getting a good night’s rest is also important for regulating emotion. Sleep deficiency has been linked to an increased risk of depression, bipolar disorder, substance use disorder and suicide.
“Sleep impacts how healthy you feel and how happy you feel because of its influence on those hormones and the shared areas,” said Melisa Moore, assistant professor of clinical psychiatry at the Children’s Hospital of Philadelphia’s division of pulmonary medicine and sleep center.
Sleep is also necessary for the body to heal and repair heart and blood vessels. Lack of sleep has been linked to an increased risk of heart disease, kidney disease, high blood pressure, diabetes, obesity and stroke, experts say.
That well-rested feeling can also be impacted by a misaligned circadian rhythm, or the internal clock that tells a person when it’s time to be asleep and when it’s time to be awake, Kolla said. Every human’s internal clock naturally follows a 24.2-hour schedule with six to eight hours of sleep at night.
Every cell in the human body has its own internal clock that follows a “master clock” located in the brain. Studies have found people who go to bed or wake up outside of this circadian rhythm suffer many of the same health consequences caused by sleep deficiency.
“Shift workers also have an increased risk of cardiovascular events, diabetes and cancer. (They) have both circadian misalignment and lack of sleep,” Flynn-Evans said.
Cognitive consequences of DST
The DOT says the switch to daylight saving time prevents traffic accidents, but data seems to suggest the opposite is true immediately after the transition.
A 2020 study, published in the peer-reviewed journal Current Biology, determined the risk of fatal traffic accidents increased by 6% in the U.S. during the spring transition to daylight saving time. Researchers found this risk was highest during the morning on the West Coast.
Experts say this may be due to the lack of morning light during daylight saving time. Light is essential to circadian rhythm because it suppresses the brain’s release of melatonin (aka the “sleep hormone), experts say.
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Drivers are less alert without morning light. During daylight saving time, they also may be suffering from the cognitive impacts of sleep loss including inattention, inability to focus and the tendency to take risks due to the inability to perceive consequences.
“Increased ER visits, increased motor vehicle crashes and fatal crashes,” Flynn-Evans said. “A lot of people think of the evening benefit (of daylight saving) without considering the impacts of the morning.”
Physical consequences of DST
Mounting evidence from years of scientific research has suggested many health consequences of sleep loss have been associated with the switch to daylight saving time.
In a 2015 study published in Sleep Medicine, researchers in Finland compared the rate of stroke in more than 3,000 people during the week following a daylight saving time transition to the rate in nearly 12,000 people two weeks before or two weeks after that week.
They found the overall rate of having a stroke was 8% higher during the first two days following the transition to daylight saving from 2004 to 2013. People with cancer were 25% more likely to have a stroke after the switch compared to any other time of the year. Participants over the age of 65 were 20% more likely.
“These are the effects of living on a social time that’s mismatched from when your body is timed,” Flynn-Evans said.
A 2019 report published in the Journal of Clinical Medicine analyzed seven studies on daylight saving time including more than 100,000 people and found a higher risk of heart attacks in the weeks following both the spring and fall transitions.
Daylight saving time is also associated with an increased risk of cancer in residents living on the West Coast, according to a 2017 study published by the American Association of Cancer Research journal Cancer Epidemiology, Biomarkers & Prevention.
People are also more likely to miss medical appointments during daylight saving time, Flynn-Evans said, which may exacerbate medical emergencies and outcomes.
“There are detrimental effects… There are no upsides,” Kolla said about daylight saving time.
Daylight saving consequences among kids, teens
Many of the cognitive consequences experienced by adults from the abrupt transition to daylight saving time also appear in children and adolescents, but health experts say it may have a greater impact on this population as school forces them to function earlier in the day.
“If we want our kids to be functioning as well as they can and be as happy as they can, then sleep is critical,” Moore said.
Sleep deficiency could affect kids’ memory consolidation and learning of new tasks, Owens said. This could be hard on smaller children who are expected to learn at rapid rates.
“It also has to do with the inattention,” she said. “If the information doesn’t get in there in the first place, it doesn’t have a good chance of being retained.”
However, adolescents may be most impacted by daylight saving time because their internal clock runs later than other age groups. During puberty, hormonal responses to light exposure change, meaning teenagers want to stay up at later and sleep in.
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This is called “sleep phase delay,” according to the Sleep Disorders Center at the University of California, Los Angeles. Early school times and late-night studying exacerbate this naturally occurring phenomenon, Kolla said, so teenagers always feel sleep-deprived.
A study published in the Journal of Neuroscience, Psychology, and Economics looked at standardized testing scores at about 350 Indiana public high schools from 1997 to 2006. Researchers compared schools in counties that switched to daylight saving time to those in counties still on standard time.
After controlling for socioeconomic status, race and ethnicity, they found SAT scores were negatively impacted by about 16 points in schools that transitioned to daylight saving time in the spring.
The switch to daylight saving time falls in the spring when schools are gearing up for the end of the year with final projects, standardized testing and exams, Moore said, creating an unnecessary burden for sleepy teenagers during an academically important time of year.
“(Daylight saving time) is not helpful and the impact on health and sleep is much greater than anything we could possibly gain,” Moore said.
Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.
