Sleep apnea, brief disruptions of breathing during the night that affect as many as 12 million Americans, increases the risk of death four- to sixfold, according to two new studies released today.
Results from the studies "remove any reasonable doubt that sleep apnea is a fatal disease," said epidemiologist Nathaniel S. Marshall of the Woolcock Institute of Medical Research in Australia, lead author of one of the two papers published in the journal Sleep.
The findings "hint" that treatment of the condition can lower the risk of death, but "studies are still needed to test that question," said Michael J. Twery, director of the National Institutes of Health's National Center on Sleep Disorders Research, which sponsored one of the studies.
Researchers had previously demonstrated an increased risk of death associated with sleep apnea in people suffering from other health problems, but this is the first time a similar risk has been demonstrated in apparently healthy people, Twery added.
Sleep apnea results when soft tissue in the back of the airway collapses and blocks it, causing an interruption in breathing that lasts 10 seconds or more. Victims of moderate to severe forms can suffer 20 to 30 such episodes per hour all night without realizing they are being disturbed.
Symptoms include daytime sleepiness, excessive snoring and morning headaches. The primary treatment is a technique called continuous positive airway pressure, or CPAP, in which pressurized air is administered through a mask. Surgery and oral appliances to prevent blockage may also be used in some cases.
In one study, conducted by epidemiologist Terry Young and her colleagues at the University of Wisconsin-Madison, 1,522 randomly selected state employees between the ages of 30 and 60 spent a night in a sleep laboratory. The researchers found that 63 of them, or 4%, had moderate to severe apnea, 20% had mild apnea, and the rest had none.
The team checked death records about 18 years after the initial tests.
They found that 12 of the subjects with moderate to severe sleep apnea (19%) had died, compared with 46 (4%) of those with no sleep apnea. Those with mild or moderate apnea had a risk 50% greater than those without apnea, but the results were not statistically significant.
The Australian study was similar, involving 380 residents of the community of Busselton between the ages of 40 and 65. Researchers found that those with moderate to severe sleep apnea were more than six times as likely to die over the 14 years of the study.
"I think many people who wrote off their snoring or apnea as a minor problem will be stunned by these findings," said Dr. Ruth Benca, medical director of the Wisconsin Sleep program, who was not involved in the research.