Obstructive Sleep Apnea Severity Linked With Death Risk

The risk of death goes up with the severity of a person's obstructive sleep apnea, according to a new study in Koreans.

The Journal of Clinical Sleep Medicine study is the first to find that sleep apnea severity is linked with death risk in an Asian population, said researchers from Chosun University Hospital, Seoul National University College of Medicine and the Seoul National University Bundang Hospital. Previous studies had only looked at Western populations.

Researchers analyzed data from 2,240 people ages 40 and older with sleep apnea or snoring who visited the Sleep Center of Seoul National University Bundang Hospital at some point between 2003 and 2009. All the study participants underwent a full-night polysomnography testing, through which researchers were able to deduce the number of times they stopped breathing throughout the night due to their sleep apnea. They were then grouped into categories based on sleep apnea severity (no sleep apnea, mild sleep apnea, moderate sleep apnea and severe sleep apnea).

All the participants who had at least mild sleep apnea (about 1,800 of the participants) were assigned to undergo surgery, CPAP, a mandibular advancement device, or a combination of the three.

The participants were followed up with until Dec. 31, 2011; the average participant was observed for 61.4 months, or a little more than five years. Of those with at least mild sleep apnea, 735 received treatment for the condition; the other 1,065 were not treated either because they refused treatment, they became lost during the follow-up period, they wanted to try losing weight, or they wanted to try sleeping in a different position.

Over the study period, 69 people (3.08 percent of the study group) died. Researchers found that the death rate was higher in the groups of people with more severe sleep apnea, compared with less severe or no sleep apnea. Specifically, 1.81 percent of people with no sleep apnea died over the study period, 2.18 percent of people with mild sleep apnea died, 3.54 percent of people with moderate sleep apnea died and 4.2 percent of people with severe sleep apnea died. Heart disease and strokes were the cause of about a third of the deaths.

Overall, the risk of dying was 2.47 times higher among people with severe sleep apnea compared with people without sleep apnea.

"The present study has a clinical implication that increased mortality, shown in studies in Western countries, is also associated with increased severity of OSA in Asians," the researchers wrote.