How many hours people sleep at night may affect their risk of stroke differently based on race, according to a study published in the October 3, 2018, online issue of Neurology, the medical journal of the American Academy of Neurology.
The study found that black men who slept less than 6 hours per night were less likely to later have a stroke when compared to black men who were average sleepers. White men who slept 9 or more hours a night were at an increased risk of stroke when compared to white men who were average sleepers. There were no differences in stroke risk by sleep duration for black or white women.
“These results suggest that short and long sleep duration may have different consequences for people depending on race and sex,” says study author Virginia J. Howard, PhD, of the University of Alabama at Birmingham and a member of the American Academy of Neurology, in a release. “More research is needed to determine the mechanisms behind these relationships. In the meantime, this emphasizes how important it is to better monitor and control cardiovascular risk factors in middle-aged to older people who have long sleep periods.”
The study involved 16,733 black and white people with an average age of 64 who had no history of stroke or problems with their breathing during sleep. A total of 37% of the participants were black. The participants were asked how many hours of sleep they usually got on work days and non-work days. Then the participants were followed for an average of 6 years to see who had a stroke.
Of the participants, 10% were short sleepers, which was defined as getting less than 6 hours of sleep, and 60% of those were black. A total of 7% of participants were long sleepers, which was defined as getting 9 or more hours of sleep, and 30% of those were black. A total of 460 strokes occurred during the study, with 172 in black people and 288 in white people.
Black men who were short sleepers were about 80% less likely to have a stroke than black men who were average sleepers. This protection for short sleepers was not present for black women, white men or white women.
In contrast, white men who were long sleepers were at 70% higher risk of stroke than white men who were average sleepers, without a significant increased risk for white women, or blacks regardless of sex.
In their analysis, researchers adjusted for other factors that could affect stroke risk, such as smoking status, diabetes, and heart disease.
The researchers found no interaction between sleep duration and age or sex alone.
Limitations of the study were that sleep hours were self-reported and people may not have remembered correctly and that the questions about sleep were asked only once and people’s sleep habits may have changed over time.