A person holds a mini red alarm clock in their hand.
Give yourself—and your heart—a little extra time to adjust on the days following spring daylight savings. (For Spectrum Health Beat)

By setting your clocks ahead one hour in the spring, you not only lose an hour of sleep, experts say you may increase your risk of a heart attack.

Conversely, that extra hour of sleep in the fall may offer some added protection.

Studies have associated the transition to spring daylight savings time with an increase in car crashes and more work injuries. No surprise there, considering the large number of bleary-eyed and exhausted people roaming about.

But research also has established a strong connection between daylight savings time changes and the incidence of heart attacks.

Tales from the front

Ryan Madder, MD, an interventional cardiologist with Spectrum Health Medical Group, is the front lines. March 9, the Monday after 2015’s spring time change, he was in the Fred & Lena Meijer Heart Center’s cardiac catheterization lab. And yes, they were “very busy,” he said.

“Several studies have demonstrated an uptick in heart attacks each Monday after the spring time change and the increase may carry into that week,” Dr. Madder said.

For one study, published in the journal Open Heart, researchers analyzed data from more than 42,000 Michigan patients admitted to hospitals throughout the state with a heart attack in the weeks before and after daylight savings time changes.

The number of heart attacks increased 24 percent on the Monday following the spring time change. In contrast, the number of heart attacks decreased by 21 percent on the Tuesday following the fall time transition.

No other days in the weeks following daylight savings time changes demonstrated significant associations for this study. And while the study found an association between daylight savings time changeovers and heart attack admissions, it did not prove cause-and-effect.

How’s time connected to the heart?

Although it may not seem like much, an hour of sleep lost or gained disrupts our chronobiologic rhythms and affects the duration and quality of our sleep for several days after each time shift.

Monday is the day of the week associated with a higher rate of heart attacks overall. Possible reasons include the mental stress and the general increase in activity that come with starting a new work week.

In addition, the most common time of day for a heart attack is early morning. This is likely related, in part, to the amount of cortisol, a hormone secreted by our adrenal gland, in our blood.

“Plasma cortisol levels naturally rise and fall in cycles during the day, peaking in the morning hours,” Dr. Madder said. “When this happens, blood pressure and heart rate also rise, and this may trigger a heart attack in some people.”

Mother Nature retains her mystery. And likes her sleep.

Given these facts, why are heart attacks still more frequent on the Monday morning after spring time change and less so the first workdays after the autumn shift?

One possible explanation: with spring forward, the population is suddenly getting up and moving earlier than they’re use to and just when cortisol levels peak and the heart is most vulnerable. With fall back, the time people wake relative to peak cortisol levels is later. In essence, they sleep past the peak, getting up when blood pressure and heart rates are at their normal levels.

“It appears to be a real phenomenon, but we still don’t know for certain why it happens,” Dr. Madder said. “It could be that the stress associated with a sudden change in schedule that affects the entire population all at once is sufficient to increase the incidence of heart attacks at the population-level. However, the risk that turning the clock forward poses on any given individual person is low, even among those with established heart disease. ”

Still, you may want to give yourself—and your heart—a little extra time to adjust on the days following spring daylight savings. Instead of getting up an hour earlier on one day, try adjusting your body’s clock a week or so in advance, getting up just 10 minutes earlier each day.

That way, by the time that “spring forward” Monday morning arrives, the time jump won’t be as startling.