Sleep Apnea Recognised as Independent Risk Factor for Mortality

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Title: Sleep Apnea Recognised as Independent Risk Factor for Mortality
URL: http://www.pslgroup.com/dg/226C9A.htm
Doctor's Guide
August 1, 2008

WESTCHESTER, Ill -- August 1, 2008 -- 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 Sleep.

Fourteen years after initial data were collected, about 33% of participants with moderate to severe sleep apnea had died (6/18), compared with 6.5% of people with mild OSA (5/77) and 7.7% of people with no OSA (22/285).

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, Woolcock Institute of Medical Research, Sydney, Australia.

"The size of the increased mortality risk was surprisingly large. In our particular study, a 6-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 Dr. 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, leaving the association between OSA and mortality in the community unknown.

The study involved 380 men and women aged 40 to 65 years 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 1 night to assess his or her level of sleep-disordered breathing. Individuals were categorised according to the frequency of recorded respiratory disturbance.

Only 3 participants had severe OSA with an average of 30 or more respiratory disturbances per estimated hour of sleep, while 18 individuals (about 4.7%) had moderate to severe OSA with 15 or more respiratory disturbances per hour.

About 20.3% (77) of participants had mild OSA with 5 to 14 respiratory disturbances per hour, and 75% (285) had no OSA.

State and national death records were reviewed through 2004 to identify participants who had died and to note the cause of death listed on the death certificates. From the records of the 33 study participants who died, no predominant cause of death could be linked to OSA.

Initial results were adjusted for other mortality risk factors such as age, sex, body mass index, smoking status, blood pressure, cholesterol, and diabetes. All statistical models produced a significant relationship between sleep apnea and mortality. No information was gathered about participants' use of any sleep apnea treatment.

According to Dr. Marshall, the results of this study indicate that OSA is a potentially life-threatening condition that demands increased medical attention.

"Our findings, along with those from the Wisconsin Cohort, remove any reasonable doubt that sleep apnea is a fatal disease," said Dr. Marshall. "People who have, or suspect that they have, sleep apnea should consult their physicians about diagnosis and treatment options."

The Wisconsin Cohort study also linked OSA to mortality risk and appears in the August 1 issue Sleep.

SOURCE: American Academy of Sleep Medicine

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