Sleep apnea increases the risk of stroke four fold

Canadians and U.S. researchers say that people who suffer from sleep apnea are at a higher risk of having a stroke than those without the condition.

Senior investigator Dr. T. Douglas Bradley of Toronto General Hospital says there is evidence dating back to the early 1970s which suggests that sleep apnea, strokes and heart attacks often happen together, but that does not mean that there is a cause/effect relationship.

In order to determine whether sleep apnea, brief episodes when breathing stops during sleep, increased the risk of stroke, Bradley and his colleagues carried out a study of 1,475 subjects.

They discovered that of the 22 people in the group who had a stroke, 5 also had severe sleep apnea.

Bradley says that association 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 smoking.

The team conducted a study of 1,189 subjects who were followed for 4 to 12 years to find out which came first, the stroke or the sleep apnea.

Their aim was to examine cases of new strokes in patients who already had sleep apnea.

In this study, the researchers were able to confirm the previous results, that for people who had sleep apnea, the chances of having a new stroke were 3.5 to 4 times greater than for those who did not have the condition.

Bradley says that in every case sleep apnea came first which is strong evidence for a cause/effect relationship.

Bradley says that these and other findings should make physicians more aware that people with sleep apnea may be at increased risk of strokes and other cardiovascular diseases, and that therefore ought to be treated.

The study is reported in the American Journal of Respiratory Critical Care Medicine, December 1, 2005.