You’d be hard pressed to find anyone who enjoys daylight savings time, the twice-yearly tradition of setting our clocks either one hour forward or backward. However, according to a preliminary study that will be presented later this year at the annual meeting of the American Academy of Neurology (AAN), it seems there are certain people who should be especially wary of daylight savings — those who are at risk of developing ischemic stroke, caused by clots that blocks blood flow to the brain.

Studying a decade’s worth of hospital admissions (2004 to 2013) in the country of Finland, the researchers found an 8 percent higher incidence of ischemic stroke in the first two days following daylight savings when compared to the two week period before and after a time transition. The temporary boost in risk appeared to be especially high for cancer patients and those over the age of 65, at 25 percent and 20 percent, respectively.

"Previous studies have shown that disruptions in a person's circadian rhythm, also called an internal body clock, increase the risk of ischemic stroke, so we wanted to find out if daylight saving time was putting people at risk," said study author Dr. Jori Ruuskanen of the University of Turku in Turku, Finland, in a statement.

Specifically, Ruuskanen and his colleagues looked at 3,033 hospitalizations during the week of a time transition, and 11,801 hospitalizations in the weeks before and after. Despite the elevated risk in the first two days, though, they failed to find any significant differences in hospital mortality following the week after transition.

It’s not the first time daylight savings has been painted as an unintentional villain by scientists. A 2013 study found that the leap ahead in March led to a 24 percent increase in heart attacks the following Monday. However, the study also found a 21 percent reduction when the clock was pushed back an hour, almost canceling out the effect.

In either case, it appears the danger of daylight savings isn’t so much about directly causing stroke or heart attack but rather in speeding along or momentarily delaying one already likely to occur. Having that knowledge in hand may still prove to be invaluable, of course, since it may enable medical professionals to better anticipate a small surge in cases following a transition as well as allow at-risk patients to take some simple steps beforehand to recalibrate their body clock, such as waking up earlier prior to the time change.

Interesting as the study is, though, the authors admit it isn’t the final word on the subject. "Further studies must now be done to better understand the relationship between these transitions and stroke risk and to find out if there are ways to reduce that risk," Ruuskanen said.

For those wondering, by the way, our clocks will have to be set a hour ahead on Sunday, March 13.

Source: Daylight Saving Time Transitions, Incidence and In-Hospital Mortality of Ischemic Stroke. AAN 68th Annual Meeting. 2016.