Over nine hours of night sleep, long noon naps raise stroke risk by 85 per cent: Study

Older people who sleep nine hours or more at night, and take long naps during the day are 85 per cent more likely to later have a stroke than people who are moderate sleepers and nappers, according to a study.

The researchers, including those from Huazhong University of Science and Technology in China, studied 31,750 people in China with an average age of 62, following them for a mean period of six years.

They said the people did not have any history of stroke or other major health problems at the start of the study but over the duration of the research, they noted 1,557 stroke cases.

The participants were asked questions about their sleep and napping habits, and the quality of rest they had.

The study, published in the journal Neurology, noted that eight per cent of the people took noon naps lasting more than 90 minutes, and 24 percent said they slept nine or more hours per night.

The results of the study revealed that people who sleep nine or more hours per night are 23 per cent more likely to later have a stroke, than people who sleep seven to less than eight hours per night.

According to the researchers, people who sleep less than seven hours per night, or between eight and less than nine hours per night, were no more likely to have a stroke than those who slept from seven to less than eight hours per night.

The study noted that the results were adjusted for other factors that could affect the risk of stroke such as high blood pressure, diabetes, and smoking.

It said people who were both long nappers, and long sleepers were 85 per cent more likely to later have a stroke than people who were moderate sleepers and nappers.

The research also revealed that people who had poor sleep quality were 29 per cent more likely to later have a stroke than people who said they had good sleep.

"These results highlight the importance of moderate napping and sleeping duration and maintaining good sleep quality, especially in middle-age and older adults," said study co-author Xiaomin Zhang from Huazhong University of Science and Technology.

Zhang emphasised that the study does not prove a causal relationship between long napping, sleeping, and stroke, but only shows an association.

The researchers said the study came with some limitations as well.

On of them was that the information on sleep and napping was taken from questionnaires, not from recording people's actual sleep.

The study also noted that data on sleep disorders such as snoring and sleep apnea were not collected.

The study involved older, healthy Chinese adults, so the results may not apply to other groups, the researchers said.