Daylight Saving Time Poses Dangerous Risks, Says Expert

Mood disturbances, cardiovascular risks, and an uptick in accidents are just a few of the possible adverse effects of daylight saving time.

On Sunday, March 10, or the late hours of March 9, most Americans will change their clocks for daylight saving time, skipping one hour ahead like those 60 minutes never existed. People in most states follow this clock change protocol, a strategy suggested by Benjamin Franklin in 1784 to take advantage of daylight and reduce candle use. However, George Hudson was the person who officially invented daylight saving time in 1895.

Yet, many individuals aren't fans of springing ahead in the spring and falling back in the fall. For instance, a 2020 American Academy of Sleep Medicine (AASM) survey found that 63% of people in the United States support eliminating daylight saving time and would prefer a fixed time year-round.

In 2023, the American Academy of Sleep Medicine (AASM) issued an updated statement on daylight saving time, stating that the U.S. "should eliminate seasonal time changes in favor of permanent standard time, which aligns best with human circadian biology."

Is daylight saving time harmful to human health?

AASM Foundation Board of Directors member Eric J. Olson, M.D., a Professor of Medicine at the Mayo Clinic Alix School of Medicine and Chair of the Division of Pulmonary/Critical Care Medicine at Mayo Clinic in Rochester, Minnesota, tells Healthnews there are several reasons why changing clocks one hour ahead harms health and public safety.

"Research shows that abrupt seasonal shifts in time disrupt our circadian rhythms, which can lead to sleep disturbances, increased fatigue, and even a heightened risk of heart attacks and strokes," Olson explains.

Regarding heart attack risks, a 2018 review of evidence found that daylight saving time, particularly the spring change, was associated with a modest increase in heart attack occurrence.

"More darkness in the morning can also increase symptoms of seasonal affective depression (SAD) disorder since morning light plays a big role in mood regulation," Olson adds.

According to Olson, public safety is impacted by changing clocks one hour ahead because losing an hour of sleep disrupts the body's sleep/wake rhythm, and this can have dangerous consequences, including an increased risk of motor vehicle accidents and medical errors.

For example, 2020 research suggests that the spring time change may increase the risk of fatal motor vehicle accidents by 6%.

"There are many risks associated with seasonal time changes, and plenty of data that supports eliminating it across the board," Olson says.

Why is adopting a permanent standard time better for human health?

The circadian rhythm, or the 24-hour sleep-wake cycle, is the timekeeper in the human body. Shifts in the body's clock can impact melatonin and cortisol levels and may increase the risks of certain health conditions. Maintaining circadian rhythms may also promote healthy aging.

"Standard time is best aligned with human circadian biology," Olson says. "During standard time, your body clock, the timing of sunrise and sunset, and local clock time are more in sync than during daylight saving time."

Olson notes that this alignment helps most people sleep better at night and feel more alert during the day.

"Essentially, people generally feel and function better when their circadian rhythm is in step with natural light cycles during standard time," Olson explains.

How to adjust to daylight saving time

Although some elected officials have tried to pass laws banning daylight saving time, the practice doesn't appear to be going away anytime soon.

However, there are a few things a person can do to make the time transition go smoother and prevent any potential health effects.

According to the AASM, tips to help manage daylight saving time include:

  • Maintain a consistent sleep routine and try to get at least seven hours of sleep per night before and after the time change.
  • Gradually adjust bedtimes and wake times by shifting them 15-20 minutes earlier each night a few nights before the time change.
  • Adjust the timing of daily routines that are "time cues" for the body, such as mealtimes or exercise schedules.
  • Consider setting clocks ahead one hour in the early evening on March 9 and then go to sleep at your regular bedtime.

Lastly, people might want to get outside early in the morning in the week after the time change, as the sunlight can help reset the body's internal clock to the new time and regulate sleep and alertness.


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