Sleep more than 9 hours and take naps? You could be increasing your risk of stroke

A new large-scale Chinese study has found that people who sleep for more than nine hours each night, or who take long naps during the day, may have an increased risk of stroke.

Carried out by researchers at Huazhong University of Science and Technology in Wuhan, the study looked at 31,750 Chinese adults with an average age of 62 and no history of stroke or other major health conditions.

The researchers asked them about their sleep and nap habits, with 80 per cent of the participants reporting that they took naps lasting more than 90 minutes, and 24 per cent saying that they slept nine or more hours per night, before following the subjects for an average of six years.

The findings, published online in Neurology, showed that after taking into account factors that could affect the risk of stroke, such as high blood pressure, diabetes and smoking, those who took a regular midday nap lasting more than 90 minutes were 25 per cent more likely to have a stroke than those who took a shorter nap lasting from one to 30 minutes.

However, people who didn't nap, or who took naps lasting from 31 minutes to one hour, were no more likely to have a stroke than people who took shorter naps lasting from one to 30 minutes.

When looking at the subjects' sleep habits, the team found that participants who slept for nine or more hours per night were 23 per cent more likely to have a stroke than those who slept for seven to less than eight hours per night, although those who slept less than seven hours per night, or between eight and less than nine hours, did not have a higher risk of stroke than those who slept from seven to less than eight hours per night.

People who were both long nappers and long sleepers were 85 per cent more likely to go on to have a stroke than moderate sleepers and nappers.

Those who said they slept poorly were also 29 per cent more likely to have a stroke than people who said their sleep quality was good.

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"More research is needed to understand how taking long naps and sleeping longer hours at night may be tied to an increased risk of stroke, but previous studies have shown that long nappers and sleepers have unfavorable changes in their cholesterol levels and increased waist circumferences, both of which are risk factors for stroke," said study author Xiaomin Zhang, MD, Ph.D., "In addition, long napping and sleeping may suggest an overall inactive lifestyle, which is also related to increased risk of stroke."

"These results highlight the importance of moderate napping and sleeping duration and maintaining good sleep quality, especially in middle-age and older adults," Zhang said.