Sleeping more than eight hours a day is associated with a higher risk for stroke, a new study has found. Researchers studied 9,692 people, ages 42 to 81, who had never had a stroke. The study tracked how many hours a night the people slept at the beginning of the study and how much nightly sleep they were getting four years later. Over the 10-year study, 346 of the study subjects suffered strokes. After controlling for more than a dozen other health and behavioral variables, the researchers found that people who slept more than eight hours a day were 46 percent more likely to have had a stroke than those who slept six to eight hours. The study, published online last week in Neurology, also found that the risk of stroke was higher among people who reported that their need for sleep had increased over the study period. The authors caution that the data on sleep duration depended on self-reports, which can be unreliable. In addition, the study identified an association between sleep and stroke risk, rather than cause and effect. Sleeping more may be an early symptom of disease that leads to stroke, rather than a cause. “It could be that there’s already something happening in the brain that precedes the stroke risk and of which excessive sleep is an early sign,” said the lead author, Yue Leng, a doctoral candidate at the University of Cambridge. In any case, she added, “we don’t have enough evidence to apply this in clinical settings. We don’t want people to think if they sleep longer it will necessarily lead to stroke.”
