In a study published in Neurology, people who took a regular midday nap that was more than 90 minutes were 25% more likely to have a stroke than those who took regular naps that were 60 minutes or less.
“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, PhD, of Huazhong University of Science and Technology in Wuhan, China. “In addition, long napping and sleeping may suggest an overall inactive lifestyle, which is also related to increased risk of stroke.”
In this study, sleeping more than 9 per night correlated with a 23% higher stroke risk compared with sleeping 7 to 9 hours per night. The results were all adjusted for other factors that could affect the risk of stroke, including high blood pressure, diabetes, and smoking. People who both took naps longer than 90 minutes and slept more than 9 hours per night had an 85% increase in stroke risk compared to those who took naps of 60 minutes or less and slept 7 to 9 hours per night.
Participants were also asked about sleep quality. People who said they slept poorly were 29% more likely to have a stroke than people who said their sleep quality was good.
Of the long nappers, 1% of cases per person-years had a stroke, compared to 0.7% of cases per person-years for moderate nappers. The numbers were the same for the long and moderate sleepers, with 1% of cases per person-years compared to 0.7% of cases per person-years having a stroke.
The study involved 31,750 people in China with an average age of 62 who had no history of stroke or other major health problems at the start of the study. They were followed for an average of 6 years. During that time, 1,557 had stroke. Participants were asked questions about their sleep and napping habits. “Midday napping is common in China,” Zhang said. “8% of the people took naps lasting more than 90 minutes, and 24% said they slept 9 or more hours per night.”
“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.
Zhang noted that the study does not prove long napping and sleeping causes stroke but only shows an association. Limitations of the study include that information on sleep and napping was taken from subjective questionnaires not objective measures and no information on sleep disorders (eg, snoring and sleep apnea) was collected. The study involved older, healthy Chinese adults, and results may not apply to other groups.