A Yale University study of 1,022 patients over the age of 50 published in this week’s New England Journal of Medicine concludes that obstructive sleep apnea more than doubles the risk of a stroke or death and that severe cases of sleep apnea more than triple the risk, even after even adjustment for other stroke-risk factors such as diabetes, hypertension and obesity. A number of previous studies have found links between sleep apnea and serious cardiovascular disease, but a link between sleep apnea and strokes had not yet been established. Strokes are the third leading cause of death in the U.S. after heart disease and cancer.

About 20% of American adults suffer from at least some form of sleep apnea, although physicians generally do not recommend treatment unless the condition involves five or more pauses in breathing per hour of sleep along with other symptoms, such as daytime drowsiness. Although only about a fifth of sleep apnea cases are considered severe, researchers and physicians estimate that more than half of the severest cases in the United States still go undiagnosed. Obstructive sleep apnea involves the muscles in the throat becoming so relaxed that the airway becomes all or partially closed, and with regard to the rarer central sleep apnea, the body temporarily stops making any effort to breathe. Common symptoms include daytime drowsiness and loud snoring, choking or gasping during sleep, although the episodes often fail to wake the person suffering from the condition.
Interestingly, one question that the Yale study does not answer is whether treating sleep apnea will reduce the incidence of strokes. In the Yale study, of the 72 sleep apnea patients who died of strokes, many of these patients were undergoing various forms of treatment for the condition. However, even with treatment, the group still had an elevated risk of stroke and death, which raises the question of whether treating sleep apnea will actually decrease the stroke risk measurably.