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Study: Daylight saving time increases the risk of stroke

Daniel Martins
Digital Reporter

Monday, March 7, 2016, 10:25 AM - Add another entry to the list of reasons to dislike Daylight Saving Time: A new study from Finland suggests the risk of suffering a stroke is increased after the clocks spring forward in March.

Researchers at the University of Turku found that the rate of people suffering ischemic stroke -- caused by a blood clot blocking blood flow to the brain -- increased by eight per cent after the clocks changed for Daylight Saving Time.

The risk was highest among people with cancer, at 25 per cent, and people older than 65, who were 20 per cent more likely to have a stroke after the time change.

However, the elevated risk didn't last beyond the first two days after the transition. And although the number of people at risk of a stroke went up, hospital deaths from stroke did not.

"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 University of Turku professor and study author Jori Ruuskanen said in a release. "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."

The group's findings will be presented at the annual meeting of the American Academy of Neurology in Vancouver this April.

Several studies over the past couple of decades have found the time change has a measurable impact on humans. 

A 2012 study, for example, found the risk of heart attacks rises by 10 per cent upon changing to Daylight Saving Time in the spring, and fell by the same amount when Daylight Saving Time ends in the fall. Some studies have also found an increase in traffic collisions.

Daylight Saving Time was proposed more than a century ago as a means to boost productivity and save power as the seasons changed. Germany became the first country to adopt it nationwide in 1916, with most other northern countries following suit within a few years.

However, some parts of Canada seem to have adopted the practice locally a few years prior. Timeanddate.com says Thunder Bay, Ont., was the first jurisdiction in Canada to try it out in 1908.

Not all Canadians are on board, however. With the exception of a few border towns, Saskatchewan does not observe Daylight Saving Time. Quebec, Ontario and Nunavut all include some communities that do not change their clocks.

SOURCES: American Academy of Neurology | Timeanddate.com | The Telegram

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