Daylight Savings Time Affects Heart Attack Risk?

October 31st, 2008

Talk about an odd study. If you were to get your passport stamped for Sweden recently you may have seen a study about how moving the clock ahead, or back has a slight effect on the risk of hear attack.

Scientists at Karolinska Institutet have examined how the incidence of myocardial infarction in Sweden has changed with the summer and winter clock-shifts since 1987.

When you move the clock forward your risk is higher according to the study in the week after the change. When the clocks are moved back, as in the Fall, the risk is slightly less.

Of course you have to take a study such as this with a grain of salt IMO. The study has been done over a 20 year period. Are we to assume this is valid? In the course of time where Daylight Savings Time has existed isn’t it possible that looking at only a 20 year range may provide many coincidences?

“There’s a small increase in risk for the individual, especially during the first three days of the new week,” says Dr Imre Janszky, one of the researchers behind the study. “The disruption in the chronobiological rhythms, the loss of one hour’s sleep and the resulting sleep disturbance are the probable causes.”

This study may actually be useful for other reasons than the headline. Another win for stress.

According to the scientists, the study provides a conceivable explanation for why heart attacks are most common on Mondays, which previous research has suggested.

“It’s always been thought that it’s mainly due to an increase in stress ahead of the new working week,” says Dr Janszky. “But perhaps it’s also got something to do with the sleep disruption caused by the change in diurnal rhythm at the weekend.”

Even though the increase and decrease in risk are relatively small for the individual, the team believes that the study can improve our understanding of how disruptions to diurnal rhythms impact on our health.

“Roughly 1.5 billion people are subjected to these clock-shifts every year, but it’s hard to make any generalised statement about how many heart attacks they can cause,” adds Dr Rickard Ljung, another member of the research team.