OSA doubles risk of stroke, study finds

Sunday, November 13, 2005

BOSTON - Obstructive sleep apnea can increase the risks for stroke and death, according to groundbreaking research. The study of nearly 700 people found a doubled risk of stroke in all those with sleep apnea, and a threefold increased risk in those with a severe case of the condition, according to the HealthDay Reporter.

"We followed people with sleep apnea forward in time to see who had strokes or died, and found this increased risk," said lead researcher Dr. H. Klar Yaggi, an assistant professor of medicine at the Yale University School of Medicine. "What our study found is a new risk factor for the development of stroke."

His team published its findings in the Nov. 10 issue of the New England Journal of Medicine.

Other studies looking at sleep apnea and stroke have been done, but they focused on the incidence of sleep apnea in people who had already suffered strokes, Yaggi explained.

Those studies found that "a high percentage of patients with stroke have sleep apnea," he said. But they didn't solve the chicken-or-egg question of whether sleep apnea helps trigger stroke, or whether stroke risk factors cause sleep apnea by affecting the brain's sleep center.

But in its three-year prospective study, Yaggi's team found that the presence of sleep apnea nearly doubled the risk of stroke or death, even after the researchers adjusted for other risk factors.

The finding closes a gap in knowledge about the relationship between sleep apnea and heart problems, said Dr. Virend K. Somers, a professor of medicine at the Mayo Clinic, who wrote an accompanying editorial.

"We know there is an association between obstructive sleep apnea and various kinds of heart disease -- hypertension, atrial fibrillation, stroke and heart failure," he said. "We've never been able to prove that sleep apnea causes these things, other than hypertension. The evidence has been mainly circumstantial, and that is especially true of people with stroke. This is probably the best data available now showing that if you have obstructive sleep apnea, you have an increased risk for stroke or death."

But there is still one more missing piece to the puzzle, Yaggi said.

"The next research has to be on the impact of treating sleep apnea," he said. "The question that this study raises is whether primary or secondary prevention would be helpful in reducing the risk."

No such trials are now underway, said Dr. Carl E. Hunt, director of the National Center on Sleep Disorders Research at the National Heart, Lung, and Blood Institute (NHLBI), which helped finance Yaggi's trial.