Wednesday October 29, 2008 (foodconsumer.org) -- A Swedish study suggests that sleeping for an extra hour may drastically reduce risk of heart attack.

The study found that when clocks were set back an hour on Monday, the number of heart attacks dropped probably because people had an extra hour to sleep.

The study found the opposite effect when clocks were set one hour forward in the spring.   The rate of heart attacks increased during the week, particularly the first three days after the start of daylight saving time.

The study was published on Thursday in New England Journal of Medicine.

For the study, Imre Janszky of the Karolinska Institute and Rickard Ljung of Sweden's National Board of Health and Welfare examined the effect of the disruptions to sleep and the change in the body's internal clock by a time change on heart attack risk.

They went through data on heart attacks for a period of 20 years between 1987 and 2006 and found that the rate of heart attacks increased 5 percent in the first week with 6 percent increase on Monday and Wednesday and 10 percent increase on Tuesday after clocks were set forward one hour in the spring.

They also found that in the autumn, when clocks were set back one hour, the rate of heart attack dipped 5 percent on Monday although the rate for the first week remained pretty much the same.

In the U.S. daylight saving time ends this year at 2 a.m. Sunday

Clock shifts disrupt sleep and reduce its efficiency. Effects on seasonal adaptation of the circadian rhythm can be severe and last for weeks. A 2008 study found that although male suicide rates rise in the weeks after the spring transition, the relationship weakened greatly after adjusting for season.--wikipedia