Daylight Saving Time linked to higher stroke risk in following days, study warns

Is Daylight Saving really necessary? Tell us what you think.
Is Daylight Saving really necessary? Tell us what you think. THE CANADIAN PRESS/AP/Charlie Riedel

Losing an hour of sleep during Daylight Saving Time makes you bleary-eyed, but new research suggests it also increases your risk of stroke in the following days.

Scientists already warn that throwing off your body’s circadian clock tampers with appetite, productivity at work and even focus while driving. Now, they say DST raises stroke risk for the following two days, especially for seniors and those with cancer.

Daylight Saving Time occurs on March 13 at 2 a.m. this year.

Finnish doctors out of the University of Turku suggest the rate of ischemic stroke – caused by a clot blocking blood flow to the brain – is eight per cent higher during the first two days after a DST transition. After that, the disparity tapers out.

“Daylight Saving Time shift is certainly a small change of merely one hour but it affects whole nations twice a year. As traditional vascular risk factors for stroke have become better controlled at least in developed countries, we need to look for other risk factors to possibly reduce the risk,” lead researcher, Dr. Jori Ruuskanen, told Global News.

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“Stroke risk is higher in the morning hours and we know from previous studies that DST changes slightly shifts the timing pattern of stroke onset,” Ruuskanen said.

READ MORE: How Daylight Saving Time affects your internal clock

He told Global News that researchers have pointed to fragmented sleep as a culprit in raising stroke risk, but that there have been no studies on DST and stroke.

For his study, his team looked at a decade of data for stroke in Finland. They looked at the rates of stroke in more than 3,000 people hospitalized during the week following DST compared to rate of stroke in nearly 12,000 people hospitalized two weeks before and after the time shift.

Risk was higher by eight per cent during the first two days after DST. People with cancer were 25 per cent more likely to have a stroke after the time shift compared to other periods. The risk was also higher for seniors who were 65 and older – they were 20 per cent more likely to have a stroke right after the transition.

Ruuskanen said that it’s still unclear what may be at play.

READ MORE: Daylight Saving Time leads to ‘massive productivity losses,’ study says

“We did not know whether stroke risk is affected by DST transitions. What is common in these situations is the disturbed sleep cycle, while the immediate mechanisms for the increased risk remain unknown at the moment,” he told Global News.

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But the eight per cent increase is “relatively small and transient” at the population level, he assured readers.

“In this sense, there is no reason for additional worry. But people should be vigilant as always for stroke symptoms,” he said.

Take care of your sleeping habits post-DST, too, he urged. Adjust your sleeping time gradually over the following days by 15 minutes per day until you’re back to your routine, he said.

READ MORE: How the end of Daylight Saving Time could affect your schedule, internal clock

The study will be presented at the American Academy of Neurology’s annual meeting in Vancouver this April.

Read more about the stroke warning signs here.

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