If you've got a weak heart, you might have a good excuse for taking Monday off next time clocks go forward in spring, researchers say. A new study finds that the daylight saving time switch is associated with a shocking 25% rise in the risk of heart attacks on the following Monday compared to other Mondays in the year, Reuters reports. The effect—much greater than estimated in previous studies—is reversed when clocks go back in fall and people get an extra hour of sleep, the study finds.
Mondays are already the worst day of the week for heart attacks, notes the lead researcher, who studied years of admissions data from Michigan hospitals. "Perhaps the reason we see more heart attacks on Monday mornings is a combination of factors, including the stress of starting a new work week and inherent changes in our sleep-wake cycle," he says in a press release. "With daylight saving time, all of this is compounded by one less hour of sleep." He says that in light of the study, hospitals should aim to have extra staff on hand the Monday after the clocks change. (Read more daylight saving time stories.)