Switching to daylight time and skipping one hour of sleep, raises the risk of heart attacks the following Monday by 25 %, compared with other Mondays of the year, said a new U.S. study.

By contrast, heart attack risk fell 21 percent later in the year, on the Tuesday after the clock was returned to standard time, and people got an extra hour's sleep, reports Fox News.

The impact of moving the clock forward and backward was seen in a database of non-federal Michigan hospitals. 

In general, heart attacks historically occur most often on Monday mornings, maybe due to the stress of starting a new work week and inherent changes in our sleep-wake cycle, said Dr. Amneet Sandhu, a cardiology fellow at the University of Colorado in Denver who led the study.

"Our study suggests that sudden, even small changes in sleep could have detrimental effects," he said.

Sandhu examined about 42,000 hospital admissions in Michigan, and found that an average of 32 patients had heart attacks on any given Monday. But on the Monday immediately after springing the clock forward, there were an average of eight additional heart attacks, he said.

"If we can identify days when there may be surges in heart attacks, we can be ready to better care for our patients," he said.