The risk of fatal or non-fatal cardiovascular events, such as heart attacks, is increased in men with severe obstructive sleep apnea, a condition in which airways become blocked during sleep and breathing stops for brief periods, a Spanish team of researchers reports.

However, treatment with continuous positive airway pressure (CPAP), a device that delivers continuous pressurized air while the patient sleeps, seems to cut this risk.

Although research has suggested a link between severe obstructive sleep apnea and cardiovascular disease, the studies have suffered from various methodologic issues, the researchers explain in this week’s issue of The Lancet.

To clarify the association between cardiac events and obstructive sleep apnea, Dr. Jose M. Marin, from Universitario Miguel Servet in Zaragoza, and colleagues conducted a study involving healthy men and men with severe obstructive sleep apnea or related conditions.

The final analysis included 264 healthy men, 377 simple snorers, 403 with untreated mild-to-moderate severe obstructive sleep apnea, 235 with severe obstructive sleep apnea, and 372 with CPAP-treated severe obstructive sleep apnea. The subjects were followed for an average of 10 years.

Patients with severe obstructive sleep apnea had significantly higher rates of fatal or non-fatal cardiovascular events than the men in the other groups. The number of fatal events was 3.5-times higher in severe obstructive sleep apnea patients than healthy subjects. The number of non-fatal events was 4.7-times higher in the severe obstructive sleep apnea group than in the healthy group.

However, patients treated with CPAP had fatal and non-fatal cardiovascular event rates that were closer to those seen in the healthy subjects.

After adjusting the data for other potential risk factors, untreated severe obstructive sleep apnea raised the risk of fatal and non-fatal cardiovascular events by 2.87- and 3.17-fold, respectively, compared with the healthy subjects.

The findings from this large, long-term study “suggest that in untreated men with severe obstructive sleep apnea, the risk of fatal and non-fatal cardiovascular events increased,” the authors state.

While there is a relation between cardiac risk and the severity of this disease, effective CPAP therapy can significantly reduce cardiovascular events, the researchers add.

SOURCE: The Lancet, March 17, 2005.