What happens to your body when daylight saving time ends? Experts explain

Daylight saving time ends on Nov. 3. Here are some of the surprising effects it can have on our health. (Photo: Getty Images)
Daylight saving time ends on Nov. 5. Here are some of the surprising effects it can have on our health. (Photo: Getty Images)

It’s that time of year again. On Sunday, Nov. 5, daylight saving time ends and we set our clocks back an hour.

Even though we’re gaining an hour — and there tend to be more health risks, including a temporarily higher rate of heart attacks, in the spring when daylight saving time starts and we lose an hour — the fall time change can still have some surprising effects on our health.

Your stroke risk goes up

Like many people, our bodies don’t like change. Simply moving the clock back or ahead one hour temporarily increases the risk of ischemic stroke, according to a 2016 Finnish study. Ischemic stroke, which is the most common type of stroke, is caused by a clot blocking blood flow to the brain, according to the American Academy of Neurology.

During the first two days after a daylight saving transition, the researchers found that the overall rate of ischemic stroke went up by 8 percent. This risk was particularly high for people over age 65, whose risk of stroke went up by 20 percent after the time change. The good news: The rates returned to normal after two days.

This appears to be caused by a disruption in the circadian rhythm — our body’s internal clock. “When there is a sudden change in the timing of environmental cues — daylight saving time, traveling through time zones, shift work — a dyssynchrony occurs between our internal circadian clocks and our behaviors, such as our sleep/wake cycle,” Martin Young, PhD, an associate professor in the Department of Medicine at the University of Alabama at Birmingham, tells Yahoo Life. “This is because there is a lag in the ‘resetting’ of our internal clocks.”

Young explains there’s a “golden rule” that it takes about one full day for our internal clocks to adjust for every hour of time change — just like with jet lag. “But not all clocks are equal,” he says. “Some rest faster than others. Typically, the central clock in our body — located in a special brain region called the suprachiasmatic nucleus — resets relatively quickly, while the clock in the heart resets much slower. This means that during the ‘resetting’ period following an abrupt change in the environment, dyssynchrony also occurs between the different organs in our body.”

But your heart attack risk goes down

That 60-minute time change has a big impact on your heart health. While the risk of having a heart attack goes up when daylight saving starts in the spring, it actually goes down when the time change ends in the fall. A study published in the journal BMJ showed a 24-percent jump in heart attack risk the Monday after daylight saving time kicked off, but the same study found that heart attack risk dropped 21 percent on the Tuesday after returning to standard time in the fall, possibly because people got an additional hour of sleep.

You may be more likely to get into a car accident

Research shows that car accidents can go up after the time change ends in the fall, likely due to it getting darker earlier. Driving in the evening is more dangerous: Although people only spend a quarter of their total driving time at night, it accounts for 50 percent of traffic deaths, according to the National Safety Council.

Your sleep schedule may be thrown off

Although you’re technically getting an hour back, Natalie D. Dautovich, PhD, an assistant professor at Virginia Commonwealth University and an environmental scholar at the National Sleep Foundation, tells Yahoo Life: “A change in the timing of our sleep, even by just an hour, can result in feelings of ‘jet lag’ until we adjust to the new change. As a result, you may feel sluggish, sleepy during the day, and have difficulty concentrating while adjusting to the change.”

But there is some good news: “A benefit of the time change in the fall is earlier exposure to daylight, which can help to synchronize circadian rhythms to the new time,” Dautovich says.

You may be more likely to deal with depression

Depression diagnoses tend to increase “immediately after” we go from daylight saving to standard time, according to Danish study. Researchers analyzed more than 185,000 reports of depression logged in the country’s Central Psychiatric Research Register between 1995 and 2012 and found that the number of people diagnosed with depression during the month after daylight saving time ended was 8 percent higher than expected. Granted, the study focused on people dealing with severe depression, but the study authors told ScienceDaily that there is no reason to believe the seasonal time change only affects those more vulnerable to severe forms of the mood disorder.

"We expect that the entire spectrum of severity is affected by the transition from daylight saving time to standard time," Søren D. Østergaard, MD, PhD, one of the study’s researchers and an associate professor at Aarhus University Hospital in Denmark, told ScienceDaily.

Østergaard added: "Furthermore, the transition to standard time is likely to be associated with a negative psychological effect as it very clearly marks the coming of a period of long, dark and cold days."

What you can do to help your body adjust

In the meantime, there are things you can do to help your body adjust to the time change this weekend.

You can start by delaying your bed and wake time in 15-minute increments in the days leading up to the time change, suggests Dautovich. “Maintain a dark bedroom environment during the morning to encourage sleeping in until your typical wake-up time,” she says. “Light exposure during the evening can help with staying awake until your typical bedtime. However, try to limit bright light exposure and electronic use within an hour of bed.”

As Young points out, “Our internal clocks are reset by both environmental and behavioral cues. These include light, physical activity, and food intake; different organs appear to be more responsive to one or more of these cues. So, one way to reset all clocks in the body is to challenge your body with all three of these cues simultaneously. This would mean when you wake up: eat a decent breakfast, expose yourself to light and be physically active.”