The findings out of the University of Alabama at Birmingham said the Monday and Tuesday after moving the clocks ahead are associated with a 10 percent increase in the risk of heart attack.
On the other hand, the risk drops by about 10 percent when the clocks move back an hour. Exactly why this happens isn't yet known, though there are several theories.
Experts say sleep deprivation, the body's circadian rhythm and immune responses can all come into play when the time changes.
