Daylight saving time increases stroke risk, scientists find
Turning the clocks forward or back by an hour at the start and end of summer may be tied to increased risk of ischemic stroke, researchers find
Daylight saving time increases the risk of having a stroke by eight per cent, researchers claim.
Turning the clocks forward or backwards by one hour at the start and end of summer may be tied to an increased risk of ischemic stroke - but only temporarily.
Previous research has shown that ischemic stroke is the most common kind of stroke, accounting for 87 per cent of all cases. It is caused by a clot blocking blood flow to the brain.
Study author Doctor Jori Ruuskanen, of the University of Turku in Finland, said: "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."
For the study, the researchers looked at a decade of figures in Finland to find the rate of stroke.
They compared the rate of stroke in 3,033 people hospitalised during the week following a daylight saving time transition to the rate of stroke in a group of 11,801 people taken to hospital either two weeks before or two weeks after that week.
They found that the overall rate of ischemic stroke was eight per cent higher during the first two days after altering the clocks for daylight saving. There was no difference after two days.
People with cancer were 25 per cent more likely to have a stroke after daylight saving time than during another period.
The risk was also higher for those over age 65, who were 20 per cent more likely to have a stroke right after the transition.
But hospital deaths from stroke did not increase in the week after a daylight saving time transition.
First introduced by William Willett in 1907, the system was designed to make use of the daytime and prevent wasting it first thing in the morning during the summer.
British Summer Time is also known as Daylight Saving Time, and Willett's idea also saw him publish a pamphlet called The Waste of Daylight.
It was designed to get people out of bed earlier in the summer, by changing the nation's clocks and boosting productivity.
Dr Ruuskanen added: "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 findings of the preliminary study were due to be presented at the American Academy of Neurology's annual meeting in Vancouver, Canada.