Sleep Duration May Influence Stroke Risk Based on Race, Gender

The influence of sleep duration on stroke risk seems to differ with regard to race and sex, new data from the national, longitudinal Reasons for Geographic and Racial Differences in Stroke (REGARDS) study suggest.

Long sleep duration (≥9 hours) among white men was associated with an increased risk for stroke, whereas short sleep duration (<6 hours) was associated with reduced risk for incident stroke among black adults of middle age or older, particularly black men.

The finding that short sleep duration may reduce stroke risk in black men is "perplexing and conflicts with other studies," the researchers acknowledge.

"The short answer to why short and long sleep duration may have differing health consequences by race and/or sex is, we do not know yet. The pathways between sleep duration and future stroke, depending on what human-defined demographic category you belong to, have not been revealed through science yet," first author Megan Petrov, PhD, Arizona State University, Phoenix, told Medscape Medical News.

"For persons with long sleep patterns, especially white men, physicians should work with their patients to pay more attention to monitoring and management of stroke risk factors," added coauthor Virginia Howard, PhD, of the University of Alabama at Birmingham.

The study was published online October 3 in Neurology.

Racial, Sex Differences

The analysis included 16,733 black and white adults aged 45 years and older (mean age, 64 years; 37% black) who did not have a history of stroke or sleep-disordered breathing.

As determined on the basis of self-reported habitual sleep duration, 10.4% of the cohort were short sleepers (<6 hours a night), and 6.8% were long sleepers (≥9 hours of sleep a night). Black adults represented 60% of short sleepers and 29.7% of long sleepers.

Over an average of 6.1 years of follow-up, 460 strokes occurred among 172 blacks and 288 whites.

In analyses adjusted for stroke risk factors, short sleep duration was significantly associated with decreased risk for stroke among blacks (hazard ratio [HR], 0.49; 95% confidence interval [CI], 0.28 - 0.85). This was most pronounced among black men (HR, 0.21; 95% CI, 0.07 - 0.69).

In contrast, long sleep duration was significantly associated with increased stroke risk among white men (HR, 1.71; 95% CI, 1.06 - 2.76) but not black men (HR. 0.55; 95% CI, 0.13 - 2.32).

There was no interaction between sleep duration and age or sex alone with regard to stroke risk.

The current results underscore the need for mechanistic, longitudinal research of sleep-stroke associations by demographic subgroups, the researchers conclude.

Petrov said it's possible that extremes in sleep duration may differentially affect cardiometabolic health risks by race and/or sex directly, because, physiologically and genetically, different racial groups, as well as men and women, may have different sleep needs that confer different levels of risk.

"However, the scientific literature does not suggest that men and women, blacks and whites have substantially different sleep needs. Instead, they have differences in actual sleep, obtained due to a variety of psychological, behavioral, sociocultural, and environmental factors.

"These sleep duration inequities combined with physiological differences between the sexes and races may confer greater susceptibility for poor health in the future for one demographic group over another," said Petrov.

Different races and the two sexes may differ with respect to how they perceive or estimate their habitual sleep duration. This in turn could have consequences for health, said Petrov.

In addition, said Petrov, "we cannot rule out that sleep duration may be a marker for another non-sleep-related variable that is actually explaining the relationship and that extremes in sleep duration just happen to be associated with that variable. One example is short sleep duration is most prevalent in those who are full-time employed, which may confer a more regular sleep and activity pattern that is health protective."

Interpret With Caution

Azizi Seixas, PhD, of the Department of Psychiatry and Population Health, New York University School of Medicine, New York City, who studies sleep and cardiovascular disease but who was not involved in the study, urged caution in interpreting the findings.

"One should not conclude," he told Medscape Medical News, "that short sleep may protect black men from stroke. That should not be the take-home message.

"The association between short sleep and stroke is very well evidenced," said Seixas. "Mechanistically, we've been able to show how chronic and habitual short sleep duration increases an individual's risk for stroke. So the finding that short sleep may be protective flies in the face of established evidence."

The finding in this study that long sleep duration may increase stroke risk is not surprising and adds to the literature, he said.

The study was funded by the National Institute of Neurological Disorders and Stroke. Dr Petrov, Dr Howard, and Dr Seixas have disclosed no relevant financial relationships.

Neurology. Published online October 3, 2018. Abstract

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