Strokes, heart attacks and traffic accidents. What do they all have in common?

Daylight saving time.

A 2020 study published in The Journal of Clinical Sleep Medicine found a spike in heart attacks and strokes during the week following daylight saving time in March. Johns Hopkins and Stanford University also published a comprehensive study showing a significant increase in car crash fatalities on the Monday following the spring change.

“Anytime there is a change in the time schedule, such as at the transition from daylight saving time to standard time and back, it can typically take the body a few days to adjust, although for some people it can take a few weeks or longer,” said Dr. Kevin A. Walker, medical director for Intermountain Healthcare’s Sleep Disorders Center.

This adjustment is typically more difficult when moving forward, like we do in the spring, Walker said, and on average people may get 30-40 minutes less sleep the Monday after.

“In addition, waking up earlier when it’s darker can be more difficult because we rely on that light exposure to signal our circadian clock to be more awake,” Walker said. ” This sleep disruption can negatively affect mood, cardiovascular health and driving safety. It’s possible that avoiding this time change could have some health and safety benefits.”

The U.S. Senate recently passed a bill to make daylight saving time permanent, opting for the spring jump forward instead of standard time, but health and sleep experts across the country aren’t so supportive.

The American Academy of Sleep Medicine issued a statement cautioning the permanent change could cause potential health risks “that could be avoided by establishing permanent standard time instead.”

“We call on the House to take more time to assess the potential ramifications of establishing permanent daylight saving time before making such an important decision that will affect all Americans,” the statement said.

“Experts do typically recommend that if we stay on one time year-round it should be standard time,” Walker said. “Studies show that people living on the most western border of time zones, which would be similar to being on daylight (saving) time, are at some increased risk for cancer.”

Walker said this could be due to more light exposure later in the evening and subsequently curtailed total sleep time. Because of light’s impact on our circadian clock, Walker said, light exposure when trying to sleep can be problematic.

“However, not all light is equal,” he said. “Short wavelength light, perceived as blue color, is the strongest synchronizing agent for the circadian system. Blue light waves are emitted for fluorescent and LED lights as well as our electronic screens. Red, orange and yellow light doesn’t seem to have this same circadian impact.”

Exposure to this light during the two hours prior to bedtime can inhibit melatonin release and make it harder to fall asleep at bedtime, which can lead to reduced total sleep time.

“Sleep deprivation has multiple health implications including negative impacts on cardiovascular disease, mood, weight and cancer, as well as driving concerns,” Walker said.

A study published by Northwestern University shows even moderate ambient light while sleeping can cause insulin resistance the next morning, putting you at higher risk for diabetes.

“Insulin resistance is when cells in your muscles, fat and liver don’t respond well to insulin and can’t use glucose from your blood for energy. To make up for it, your pancreas makes more insulin. Over time, your blood sugar goes up,” said Dr. Phyllis Zee, chief of sleep medicine at the Northwestern University School of Medicine. “Now we are showing a mechanism that might be fundamental to explain why this happens. We show it’s affecting your ability to regulate glucose.”

Walker said any light at night can make it harder to sleep because the eyelids are so thin, they don’t fully block out light, even when closed, and some people are more sensitive to the impact of light in the room than others.

“A night light for safety or other reasons may be OK, but it should be dim and placed so as not to cast excessive light on you while sleeping,” he said.

Dr. Ivy Mason, research fellow at Harvard Medical School and post-doctoral fellow at Northwestern University, said in addition to sleep, nutrition and exercise, light exposure during the daytime is an important factor for health — but during the night, even modest intensity of light can impair heart and endocrine health.

While daylight saving time has already occurred this year, experts do have some tips to help:

• Use blackout curtains or eye masks to block outdoor light.
• Move your bed away from the window.
• Stay away from blue or white light while sleeping.
• Keep the lights off and the room as dark as possible.

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