Sleep apnea hikes risk of death, UW study finds
A new study conducted by a team of University of Wisconsin researchers shows that people suffering from severe sleep apnea have three times the risk of dying due to any cause compared to people without the disorder.
Sleep apnea is a condition with repeated episodes of breathing pauses during sleep despite an ongoing effort to breathe. Apnea often occurs when muscles in the back of throat relax, causing soft tissue to collapse and temporarily block the air passage.
The study, published in the Aug. 1 issue of Sleep, was led by Dr. Terry Young, professor of epidemiology at UW-Madison's School of Medicine and Public Health. The findings are the result of an 18-year follow-up of 1,522 participants in the Wisconsin Sleep Cohort Study, which was comprised of a random sample of men and women between the ages of 30 and 60.
The original participants, who were all state employees, spent one night at UW's General Clinical Research Center beginning in 1988 to determine whether they suffered from sleep apnea. Sixty-three of the participants, or roughly 4 percent, were found to suffer from severe sleep apnea, experiencing between 30 and 97 apneas per hour. About 76 percent of the subjects had no sleep apnea.
Young's recent findings involved reviewing death records of initial participants to determine if those suffering from sleep apnea had a higher mortality rate over the 18-year period. The doctor found that participants suffering from severe sleep apnea had died at a rate three times as that of those without the disorder. Eighty of the original 1,522 participants -- 5.3 percent -- had died as of March 1, 2008.
As part of the study, which was funded by the National Heart, Lung and Blood Institute, the participants return to UW every four years and stay overnight for re-evaluation. Young said about 90 percent of the original participants come back every four years, including many who have moved away from Wisconsin.
"They have been extraordinary," Young said of the participants.
Young said about 10 percent of adults suffer from at least moderate sleep apnea, which is characterized by 15 or more breathing pauses per hour. Someone with a severe form of the disorder experiences 30 or more breathing pauses per hour.
According to Young, being overweight is the primary risk factor for developing sleep apnea, and for those already suffering from the disorder, being overweight can make the condition worse.
People with sleep apnea will sometimes wake up gasping for air, perhaps feeling as if they are choking. But even those with severe cases of the disorder may not realize it.
"Most people will not notice their own sleep apnea," said Young.
For many years, the medical community did not consider the importance of sleep in health, said Young, and the most common symptoms of sleep apnea, loud snoring and feeling tired during the daytime, even after sufficient sleep, were too often trivialized by medical practitioners.
"The medical field was largely unaware of the disorder until recently," Young said. "As a result, not many people suffering from the disorder were actually diagnosed."
"We really feel that the Wisconsin Sleep Cohort participants helped discover something important," said Young. "They are pioneers who slept for science."
For more information on sleep apnea, go to www.sleepfoundation.org.
File photo
A UW-led study says people with sleep apnea have three times the risk of dying.
