Sleep apnea could signal greater danger.

The nighttime breathing disorder known as obstructive sleep apnea doubles a person's risk of stroke or death, a new study suggests.

In this form of apnea, a person's breathing halts for at least 10 seconds at a time during sleep, typically when relaxed muscle or fatty tissue in the throat covers the windpipe. The resulting interruptions in oxygen flow to the brain and heart cause the lungs to work harder, finally tripping a fight-or-flight reflex that arouses the sleeper just enough to catch his or her breath. The outcome disrupts sleep and can harm the heart.

H. Klar Yaggi, a pulmonary and critical-care physician at the Yale School of Medicine, and his colleagues studied 1,022 people over age 50 suspected of having sleep apnea. After observing these people during a full sleep cycle and monitoring their breathing, heart rate, and other vital signs, the researchers determined that roughly two-thirds had moderate-to-severe sleep apnea. The others were just heavy snorers or had unrelated sleeping problems.

Over the next 3 years, more than twice as many study participants diagnosed with sleep apnea had a stroke or died of that or another cause than did people without sleep apnea. The scienfists report the finding in the Nov. 10 New England Journal of Medicine. The heightened risk of stroke probably stems from "cyclical drops in oxygen levels and [consequent] surges in blood pressure and heart rate," Yaggi says. Devices that pump air into a small mask fitted over the nose during sleep can keep air flowing into the throat and prevent the air passage from collapsing, he says.