Sleep Apnea Tied to Higher Risk of Stroke

NEW YORK (Reuters Health) - People with sleep apnea are at a higher risk of having a stroke than those without the condition, Canadian and US researchers report.

Senior investigator Dr. T. Douglas Bradley of Toronto General Hospital, told Reuters Health that "evidence going back to the early 1970s suggests that sleep apnea, strokes and heart attacks often happen together, but that doesn't mean that there is a cause/effect relationship."

To determine whether sleep apnea -- brief episodes when breathing stops during sleep -- increases the risk of stroke, Bradley and his colleagues conducted a study of 1,475 subjects. The researchers found that of the 22 people who had a stroke, 5 also had severe sleep apnea.

"The association," said Bradley, "was four times greater than in patients who did not have sleep apnea, even after controlling for risk factors such as diabetes, high-blood pressure (and) cigarette smoking."

To find out which came first, the stroke or the sleep apnea, the team conducted a study of 1,189 subjects who were followed for 4 to 12 years. The aim was to examine cases of new strokes in patients who already had sleep apnea.

In this study, reported in the American Journal of Respiratory and Critical Care Medicine, the researchers confirmed the previous results. For people who had sleep apnea, the chances of having a new stroke were 3.5 to 4 times greater than for those who didn't have sleep apnea.

"In every case," Bradley said, "sleep apnea came first. That's a strong evidence for a cause/effect relationship."

These and other findings, he concluded, "should make physicians more aware that people with sleep apnea may be at increased risk of strokes and other cardiovascular diseases, and that therefore, they ought to be treated."

SOURCE: American Journal of Respiratory Critical Care Medicine, December 1, 2005.