Moving the clock forward or backward may alter the timing of when heart attacks occur in the week following these time changes, the study said. (Agencies)
"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," said Amneet Sandhu, cardiology fellow at University of Colorado in Denver.
"With daylight saving time, all of this is compounded by one less hour of sleep," he said. Daylight saving time or summer time is the practice of advancing clocks by an hour near the start of spring so that evenings have more daylight and mornings have less.
The researchers used Michigan's BMC2 (a collaborative consortium of health care providers in the State of Michigan) database, which collects data from all non-federal hospitals across the state, to identify admissions for heart attacks requiring percutaneous coronary intervention from Jan 1, 2010 through Sep 15, 2013.
Data from this largest study of its kind in the US revealed a 25 percent jump in the number of heart attacks occurring the Monday after we "spring forward" compared to other Mondays during the year - a trend that remained even after accounting for seasonal variations in these events.
But the study showed the opposite effect was also true. Researchers found a 21 percent drop in the number of heart attacks on the Tuesday after returning to standard time in the autumn. The study is to appear in the journal Open Heart.
Moving the clock forward or backward may alter the timing of when heart attacks occur in the week following these time changes, the study said.