Daylight Saving Time Linked to Stroke Risk
Opponents of Daylight Saving Time (DST) range from dairy farmers whose cows get confused, to religious groups whose services occur at sunrise or sunset. Now those disgruntled clock-watchers may have a new weapon in their fight to ban the time change.
A research team from the University of Turku in Finland has found that moving the clock forward or back by an hour increases the risk of stroke.
Investigators used data from 3,033 individuals hospitalized during the week after a DST transition and compared it with the rate of stroke in a group of 11,801 people who were hospitalized 2 weeks before or 2 weeks after the clock change.
For the first 2 days after the DST switch, the overall rate of ischemic stroke was 8% higher. After 2 days, the levels were back to normal. Certain groups saw higher risks -- people with cancer were 25% more likely to have a stroke just after the transition than any other period. Also, individuals over the age of 65 were 20% more likely to have a stroke immediately after the shift.
Previous research has discovered some circadian influence on stroke levels. One study found that the chance of an ischemic stroke between midnight and 6 a.m. was 55% higher than at any other time of the day. It seems that timing is somehow important in how strokes occur, but this is the first time that daylight saving has been specifically investigated as a risk factor.
Stroke kills around 130,000 Americans every year (about 1 in 20 total deaths). The most common type of stroke is ischemic, accounting for 85% of all strokes.