Moderate to severe obstructive sleep apnea (OSA) is an independent risk factor for all-cause mortality, according to a study in the August 1 issue of the journal Sleep.
Fourteen years after initial data were collected, about 33 percent of participants with moderate to severe sleep apnea had died (six of 18 individuals), compared with 6.5 percent of people with mild OSA (five of 77) and 7.7 percent of people with no OSA (22 of 285). The association between moderate to severe OSA and mortality remained significant after statistical adjustment for other risk factors, producing a fully adjusted hazard ratio of 6.24 for all-cause mortality; mild OSA was not a risk factor for mortality.
"This is the first study to demonstrate an independent association between all-cause mortality and sleep apnea in a community-based study," said lead author Nathaniel Marshall, PhD, a postdoctoral fellow at the Woolcock Institute of Medical Research in Sydney, Australia. "The size of the increased mortality risk was surprisingly large. In our particular study a six-fold increase means that having significant sleep apnea at age 40 gives you about the same mortality risk as somebody aged 57 who doesn't have sleep apnea."
According to Marshall, previous studies that have linked OSA to mortality as an independent risk factor have involved patients referred to sleep clinics rather than community-based samples; the association between OSA and mortality in the community was unknown.
The study involved 380 men and women between the ages of 40 and 65 who were already involved in the Busselton Health Study, an ongoing survey of residents in the rural town of Busselton in the state of Western Australia. From November to December 1990, each participant used a portable home-monitoring device for one night to assess his or her level of sleep-disordered breathing.