by Charles Bankhead

Severe obstructive sleep apnea almost tripled stroke risk in men, data from a prospective cohort study showed.

Among men with mild or moderate apnea, each one-unit increase in the obstructive apnea hypopnea index (OAHI) raised stroke risk by 6%. Obstructive sleep apnea did not have a significant association with stroke risk in women, investigators reported online in the American Journal of Respiratory and Critical Care Medicine.

“This study provides compelling evidence based on eight years of prospective data from a large, geographically diverse community-based cohort of middle-age and older adults that modest to severe levels of sleep apnea increase risk of stroke in men, suggesting the need to evaluate the role of sleep apnea treatment in ameliorating stroke risk,” Susan Redline, MD, of Case Western Reserve University in Cleveland, and colleagues concluded.

The findings add to a growing volume of evidence implicating obstructive sleep apnea as a risk factor for stroke.

For example, a community-based study of older adults showed a 2.5-fold increased risk of stroke in people with severe apnea (Stroke 2006; 37: 2317-21). However, that analysis did not adjust for confounders other than age and sex, the authors noted.

Another cohort study showed a four-fold increased risk of stroke in association with severe apnea, but the small number of strokes that occurred during follow-up limited the study’s statistical power (Am J Respir Crit Care Med 2005; 172: 1447-51).

Two other studies showed a twofold increased risk of a composite cardiovascular endpoint that included stroke among patients referred for evaluation of sleep disorders (Lancet 2005; 365: 1046-53, N Engl J Med 2005; 353: 2034-41). However, use of a composite endpoint left the association between apnea and stroke unclear.

To address some of these limitations in previous studies, investigators analyzed data from the Sleep Heart Health Study, a multicenter prospective cohort study designed to evaluate the cardiovascular consequences of obstructive sleep apnea. The analysis included 5,422 participants with no history of stroke or treatment for sleep apnea at baseline.

The baseline assessment for each participant included questionnaires about sleep habits, general health, and medication use. Testing and measurements included anthropometry, blood pressure, and overnight unattended polysomnography.

At three- and five-year follow-up visits, polysomnography was repeated, and patients completed a survey about diagnosis and treatment of obstructive sleep apnea.

During a median follow-up of 8.7 years, 193 strokes occurred, resulting in an estimated incidence of 4.4 ischemic stroke per 1,000 person-years for men and 4.5 per 1,000 person-years in women. In both sexes, stroke was associated with older age, higher systolic blood pressure, use of antihypertensive medication, and atrial fibrillation.

Among men and women who had strokes, the rate of moderate or severe obstructive apnea at baseline (OAHI >15 events per hour) was about 30% greater than among participants who remained stroke free. In men and women, the incidence of stroke increased with OAHI, and a similar association was observed for desaturation index.

In covariate-adjusted proportional hazard models, ischemic stroke was significantly associated with OAHI in men (P=0.016). Men in the top quartile for OAHI (>19 events per hour) had a hazard ratio for stroke of 2.86 (95% CI 1.1 to 7.4) compared with men in the lowest OAHI quartile (<4.1 events per hour).

In women, stroke risk was not significantly associated with OAHI quartiles. Stroke risk in women increased only when OAHI events exceeded 25 per hour.

“These prospective data provide evidence that men with increasing OAHI levels experience an increase risk of stroke,” the authors wrote. “In this data set, the effect size for stroke for OAHI levels in the upper quartile was comparable to that for a 10-year increase in age or atrial fibrillation.”

Charles Bankhead is a MedPage Today staff writer.

Originally published in MedPage Today. Visit MedPageToday.com for more sleep disorder news.