Daylight saving time may mess with your sleep, not your heart
As most Americans turn their clocks forward, one new study challenges a long-standing concern: that daylight saving time disrupts sleep enough to trigger a surge in heart attacks.
In a sweeping analysis of nearly 170,000 patients over about a decade, researchers at Duke University School of Medicine found no significant increase in heart attacks during the weeks surrounding daylight saving time transitions, either in spring or fall. The findings were published in JAMA Network Open.
Earlier, smaller studies had suggested the springtime change might lead to a temporary rise in cardiovascular events.
“We had a really nice, large data set,” Dr. Jennifer Rymer, a cardiologist at Duke Health and a co-author of the study, told Straight Arrow News. “It’s the largest data set of all heart attacks in the United States, so it’s pretty much all U.S. hospitals.”
The research drew on the American College of Cardiology’s Chest Pain MI Registry, examining cases of acute myocardial infarction from 2013 through 2022. Researchers analyzed the timing of heart attacks in the weeks before and after both the spring and fall clock changes.
One advantage of the dataset was the ability to compare states that do not observe daylight saving time, including Arizona and Hawaii, with those that do.
“We were lucky and fortunate to have a lot of data from Arizona and Hawaii that, of course, don’t participate in daylight saving time,” Rymer said. “So, we were able to use them as controls.”
The results showed no meaningful increase in heart attacks linked to the clock changes. The only notable exception was a spike in cases following the spring 2020 transition, coinciding with the onset of the COVID-19 pandemic.
The findings may offer reassurance to people worried about the health effects of losing or gaining an hour of sleep.
“There’s quite a bit of evidence that disruptions in sleep schedules can increase cardiovascular risk,” Rymer said. “So, it was nice to see that over this very large population of patients, we didn’t see a clear association between these time changes and that risk.”
Sleep disruption remains a concern for heart health, however. Cardiologists have long observed that heart attacks frequently occur during overnight hours, when changes in the body’s stress hormones and sleep patterns can trigger plaque rupture in arteries.
Still, Rymer said the one-hour shift may not be enough to meaningfully affect cardiovascular risk, especially as Americans’ work schedules have evolved.
“I think the premise is that this is a short burst — a one-hour change in one direction or the other,” she said. “The way we live and work has changed a lot over the last decade.”
The COVID-19 pandemic accelerated shifts toward remote work and more flexible hours, potentially making it easier for people to adjust to the time change, she added.
Rymer said improving awareness of sleep health is an ongoing focus for researchers and clinicians.
“As clinicians, we’re not always good about talking to our patients about sleep hygiene and sleep health,” she said. “Understanding the risks of poor sleep and conditions like sleep apnea is really important for preventing heart attack and stroke.”
Still, Rymer said the new findings help answer a question that has lingered for years.
“This study had the largest population of the ones previously done,” she said. “I think it finally really answers this question.”
Ella Rae Greene, Editor In Chief
