A common breathing disorder that disrupts sleep also, over time, increases the risk of death, a study in the August Sleep suggests. But people who use a nighttime breathing apparatus face less risk, the research shows.

Obstructive sleep apnea is a disorder marked by gaps in breathing during sleep that rob the blood of oxygen until a person gasps for air. People with apnea stop breathing many times in an hour, which can jar them out of restful sleep and wreak havoc with blood pressure, heart rate and internal stress responses.

In the United States, about one in six people may have sleep apnea, with one-fourth of those cases severe, Terry Young, an epidemiologist at the University of Wisconsin–Madison, estimates.

Sleep apnea has received widespread attention as a health problem in the past 15 years, but data generated by Young’s team suggest 85 percent of sleep apnea cases still go undetected.

While studies have suggested it carries risks, no study had, until now, tracked a population of healthy, middle-aged individuals for more than a decade to measure apnea’s effects.

The new findings come from a Wisconsin sleep project in which Young and her colleagues monitored the long-term health of 1,522 state employees, some starting in 1988. While some of the volunteers were overweight, all were otherwise healthy upon entry to the study. Their average age at that time was about 50.

At the outset, the scientists assessed each person’s sleep in a laboratory and found that, while most of the volunteers slept normally, 365 had sleep apnea. Of these, 63 people had severe apnea in which they experienced 30 or more breathing stoppages per hour.

Researchers have monitored the study participants for 14 years on average, tracking some for nearly 19 years. Death certificates over that time show that the people with severe sleep apnea were more likely to die than people without the condition, the researchers report.

“This study establishes clearly that sleep apnea is not benign,” Young says. People with milder apnea didn’t die in statistically greater numbers than those without the condition, but mild cases often progress to worse apnea, she says.

Upon entering the study, the people who didn’t have sleep apnea were borderline overweight on average, whereas those with severe sleep apnea had an average weight that is considered obese. Indeed, sleep apnea can result from obesity.

“Fat accumulation in the airway makes the airway walls thicker, softer and more likely to collapse,” says Michael Twery, director of the National Center on Sleep Disorders Research at the National Heart, Lung, and Blood Institute in Bethesda, Md.

But sleep apnea can also result from large tonsils, tightened throat muscles, a history of smoking or just a smaller-than-normal air passage. Even with adjustments for differences among the study participants in body weight, age and gender, those with severe apnea were still three times more likely to die, says Young.

The most common treatment for sleep apnea requires a person to wear a small mask during sleep. The device delivers gently forced air to the nose or mouth, keeping the airway open.

In this study, two-thirds of the people diagnosed at the outset with apnea chose not to use the devices during the time of the study. People with severe apnea who went untreated were four times as likely to die as those without the disorder, suggesting that using the masks increases survival, Young says.

Some people find the mask uncomfortable or the air-pumping machine too loud. Others pull their mask off unwittingly at night or complain of dried nasal passages.

“It’s encumbering and unnatural,” says Twery. “And it’s not attractive in bed.” But the machines work, he says.

Sleep apnea is rarely fatal on its own. In this study, deaths were mainly attributable to heart problems, stroke or cancer. When deprived of oxygen, the body responds as if confronted with an emergency, Twery says. This response pulls a person out of a deep, restful sleep to a point of semi-arousal — enough to start breathing again but not wake up. The process sabotages deep sleep. The release of stress hormones jumps and the continuing exposure to stress can have larger effects, such as chronic inflammation, he says.

“This may exacerbate existing problems indeed,” Young says.

Sleep apnea also increases daytime sleepiness and, although it didn’t show up in this mortality study, has been linked to accidents.

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