If you’re the kind of person who sleeps nine or more hours a night or takes long afternoon naps, you may want to worry about your stroke risk, a new Chinese study suggests.

According to the research, people who sleep and nap too long may increase their risk for stroke by 85%. Regular 90-minute midday naps can raise the risk 25%, compared with not napping or napping for only 30 minutes.

Only an association

“People, especially middle-aged and older adults, should pay more attention to their time spent in bed attempting to sleep and midday napping, and sleep quality, because appropriate duration of sleep and nap, and maintaining good sleep quality may complement other behavioural interventions for preventing stroke,” said researcher Dr Xiaomin Zhang. He is a professor in the Department of Occupational and Environmental Health at Huazhong University of Science and Technology in Wuhan, China.

Zhang cautioned that these findings don’t prove long napping and sleeping cause stroke, only that there is an association.

It’s not clear how sleep and the risk for stroke are connected. Other studies, however, have found that excess sleep and poor sleep quality are linked to high cholesterol and obesity, both of which are risk factors for heart disease and stroke. Zhang said.

For the study, Zhang’s team collected data on nearly 32 000 people in China whose average age was 62. During an average of six years of follow-up, more than 1 500 participants suffered a stroke.

The researchers took into account factors that can increase the risk for stroke, such as high blood pressure, diabetes and smoking.

Increased risk for stroke

Even so, they found that those who slept nine or more hours per night were 23% more likely to have a stroke, compared with people who slept seven hours or less per night.

People who slept long hours at night and took long naps during the day were most at risk for stroke, the researchers found.

Disturbed sleep was also tied to a 29% increase in the risk for stroke, compared with people whose sleep quality was good.

The study had a couple of limitations. First, the findings were based on self-reported sleep habits, and second, these findings may only apply to older people.

Neurologist Dr Salman Azhar, director of stroke at Lenox Hill Hospital in New York City, thinks that improving the quality of your sleep is more important than sleeping more.

“Number one, addressing sleep apnoea, which is underdiagnosed and undertreated,” he said. “This study confirms what other studies have shown – that insomnia and sleep apnoea are bad for you and increase your risk of stroke.”

Limited activity

Secondly, there’ s clearly some relationship between extended sleep hours or extended midday naps and increasing stroke risk, Azhar said.

“If you sleep so much, you’re actually decreasing your activity and a reduction in activity leads to a number of things that increase your risk of obesity, poor sugar control and blood pressure being out of whack,” he said.

The bottom line, Azhar believes, is that too much sleep or poor sleep limits your activity, which in turn increases your risk for stroke.

The report was published online in the journal Neurology.

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