Disclosures: Klerman reports being a member of Society for Research and Biological Rhythms. Watson is past president of AASM.
March 06, 2020
6 min read

Sleep experts say daylight saving time change needs to go

Disclosures: Klerman reports being a member of Society for Research and Biological Rhythms. Watson is past president of AASM.
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Elizabeth Klerman
Elizabeth B. Klerman

Some sleep experts want to establish a permanent standard time nationwide.

“I can't think of any medical benefit that comes from keeping daylight saving time,” Elizabeth B. Klerman, MD, PhD, an associate professor in the department of neurology at Massachusetts General Hospital and Harvard Medical School, told Healio Primary Care.

Healio Primary Care spoke with Klerman and Nathaniel F. Watson, MD, MSc, director of the Harborview Sleep Clinic and co-director of the University of Washington School of Medicine Sleep Center, about the history of daylight saving time, the health implications of changing our clocks, and how physicians can advocate for a permanent change.

A nearly 240-year old debate

Watson told Healio Primary Care the concept of daylight saving time was likely first mentioned by Ben Franklin, who satirically wrote in 1784 that “lazy Parisians could save money on candle wax if they woke earlier to take advantage of morning sunlight.”

Reference: American Academy of Sleep Medicine.

More than a century later, an entomologist from New Zealand proposed a 2-hour time shift so he would have more daylight hours after work for hunting each summer, according to National Geographic. In 1902, a British builder unsuccessfully proposed daylight saving time to English lawmakers.

Watson said the biannual clock adjustments became a reality in 1916, when lawmakers in the United States, Germany and the United Kingdom instituted daylight saving time to cut down on coal use during World War I. The federal government nullified and then reinstituted daylight saving time several times in the 20th century because of war and oil embargoes. Watson said that some states even briefly instituted their own daylight saving laws.

“There was a time when you could take a 45-minute bus ride from West Virginia to Ohio and your time would change 7 times,” Watson said.

The passage of the Uniform Time Act in 1966 established the daylight saving time standard that most of the U.S. follows today, Watson said.

However, “the law only says if an entity is going to recognize daylight saving time, it has to be on the dates that are specified [by the government],” Watson said. “Any state in the country today can make a decision to be on permanent standard time. Period, end of story.”

Daylight saving time’s impact on health

Klerman, told Healio Primary Care that the 1-hour time change significantly affects the body’s circadian system.

“The circadian system governs when we feel alert, feel sleepy, feel hungry and many other physiological processes,” she said. “Our body knows the time of day by light going through the eyes. When body clocks are out of sync with sun time, physiology is affected.”

According to researchers, some of the health consequences of adjusting our clocks include:

  • The risk for fatal motor vehicle accidents increased 6% in the week immediately following the transition to daylight saving time.
  • An estimated 28 fatal accidents could possibly be avoided in the U.S. each year if daylight saving time was abolished.
  • There was a significant increase in hospital admissions for atrial fibrillation following the transition to daylight saving time.
  • Among 1,604 pregnancies resulting from invitro fertilization, there were 24.3% more miscarriages when embryo transfers occurred 21 days after daylight saving time began compared with the number of miscarriages when the embryo transfer occurred before or outside that 21-day window.
  • There was an increase in sick leave among patients with ulcerative colitis vs. those without the condition (12.88 per 1,000 vs. 15.18 per 1,000) following the transition to standard time.
  • There was an increase in sick leave among patients with Crohn’s disease vs. those without the condition (15.88 per 1,000 vs. 18.6 per 1,000) following the transition to standard time.

Klerman noted that other conditions caused by circadian misalignment include jet lag and social jet lag (the delay in sleep timing on weekends) and conditions experienced by those who work night or rotating shifts.

In those groups of people, “there are many published reports of the medical and safety problems, including increased risks of cardiovascular, metabolic, gastrointestinal and psychiatric symptoms and weight gain, as well as increased performance errors and accidents,” she said.

Case for keeping the status quo

In support of daylight saving time, the U.S. Department of Transportation put a 21st century spin on the same arguments that were first made centuries ago.

“[Daylight saving time] saves energy,” the U.S. Department of Transportation website states. “People tend to spend more time outside in the evenings during daylight saving time, which reduces the need to use electricity in the home. Also, because the sunrise is very early in the morning during the summer months, most people will awake after the sun has already risen, which means they turn on fewer lights in their homes.” The agency also cites fewer traffic injuries and traffic fatalities because of daylight saving time — contrary to the evidence Klerman cited — as well as fewer criminal acts.


Other supporters of keeping the biannual clock changes include the Conference of Catholic Bishops, United Synagogue of Conservative Judaism and the National Parent-Teacher Association, according to reporting by The New Republic. The article added that these groups do not want their congregations and young children trekking to services or school before dawn.

Mitigating the risk

According to the American Academy of Sleep Medicine (AASM), acute adverse events tied to the time change can last about 5 to 7 days.

To mitigate any health risks, AASM recommends that individuals get at least 7 hours of sleep each night before and after the clocks are changed. They also recommend going to bed 15 to 20 minutes earlier each night 2 to 3 days before the springtime clock change and heading outdoors on the morning the springtime change takes effect to adjust to the daylight.


Advocating for change

A 2019 USA Today article indicated that Alabama, Arkansas, Florida, Nevada, Oregon, Tennessee and Washington have approved legislation to make daylight saving time permanent.. At least 10 other states have proposed changes to how they observe daylight saving time.

At the federal level, the bipartisan Sunshine Protection Act — a bill that would make daylight saving time permanent — has stalled in a Senate committee.

Klerman encouraged physicians to visit the Society for Research and Biological Rhythms’ website to arm themselves with information and advocate for change.

“It’s got a press kit. It's got talking points. It’s got the data we know, and it’s got great infographics that put the facts out there to get the advocacy started,” said Klerman, a member of that society.

Klerman acknowledged that scientists and physicians are often waiting for the “perfect study” to prove the effects of daylight saving time on human health.

“We're always looking for better evidence and more evidence,” she said. “But policymaking happens in real time, and so scientists and physicians are also encouraged to help promote ending daylight saving time now.”

Watson, a past president of the AASM, also encouraged physicians to get involved.

“Let's be clear, the idea of daylight saving time doesn't save a single second of daylight,” he said. “Daylight saving time impacts everybody. Doctors need to engage on this issue for the sake of individual and public health.” – by Janel Miller


Blakemore E. Daylight saving time 2019: The odd history of changing our clocks. https://www.nationalgeographic.com/news/2018/03/daylight-savings-time-arizona-florida-spring-forward-science/. Accessed Feb. 27, 2020.

Bote J. Daylight saving time is ending this weekend. These states want to make DST permanent. https://www.usatoday.com/story/news/nation/2019/10/29/daylight-savings-time-2019-what-states-want-make-dst-permanent/2494759001/. Accessed Feb. 27, 2020.

Chudow JJ, et al. Sleep Med. 2020;doi:10.1016/j.sleep.2020.01.018.

Congress.gov. S. 670. Sunshine Protection Act of 2019. https://www.congress.gov/bill/116th-congress/senate-bill/670. Accessed Feb. 27, 2020.

Föh B, et al. Front Med. 2019;doi:10.3389/fmed.2019:10.3389/fmed.2019.00103.

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Liu C, et al. Chronobiol Int. 2017;doi:10.1080/07420528.2017.1279173.

U.S. Department of Transportation. Daylight saving time. https://www.transportation.gov/regulations/daylight-saving-time. Accessed Feb. 27, 2020.

U.S. Department of Transportation. Uniform time. https://www.transportation.gov/regulations/time-act. Accessed Feb. 27, 2020.

Youngsmith B. How George W. Bush ruined daylight saving time. The New Republic. https://newrepublic.com/article/79023/roll-back-the-bush-changes-daylight-saving-time. Accessed Feb. 27, 2020.

Disclosures: Klerman reports being a member of Society for Research and Biological Rhythms. Watson is past president of AASM.

*Editor’s note: This story was updated on April 6, 2021, to clarify that some sleep experts support making daylight saving time permanent.