Why You May Be Less Likely to Die of a Heart Attack Tomorrow

I woke up disoriented this morning, firstly because I’d forgotten about the fall shift back in our clocks, and secondly because it took several minutes of concerted thinking and sleepy Internet research before I managed to regain, at least for this year, what is always a slippery understanding of the rationale behind Daylight Saving Time and how it affects my life—as opposed to the lives of long-ago American farmers. (Oh, sorry, is my disdain showing?)

Anyway, I decided to find out if any interesting scientific research had been conducted into the horrible-terrible-no good-very bad results of DST, and found the usual papers about how the transitions disorient people’s chronobiological rhythms and thereby lead to traffic accidents and bad days at the stock market (or maybe not). I also found an interesting study on time changes and heart health by two Swedish researchers.

This time last year—precisely two days before the end of DST in their country—Rickard Ljung and Imre Janszky published a paper explaining what they’d discovered by examining Swedish hospital records for the twenty year period spanning 1987-2006. On the first three weekdays after the springtime shift in clocks, they said, the number of cases of acute myocardial infarction (commonly known as heart attack) at hospitals around the country was significantly higher than it was on the same days two weeks before and two weeks afterwards.

With the fall shift, the effect was reversed, and slightly briefer: Significantly fewer patients than usual showed up with heart attacks on the first weekday afterward. The researchers postulate that the minor sleep deprivation associated with moving clocks forward has an adverse effect on cardiovascular health, while the hour’s extra sleep you get when the clocks move backward has a protective effect.

I still think it’s dumb that we do this DST thing at all, but it’s good to know the three gigantic cups of coffee I had today are less likely to stop my heart this Monday than most others.