Sleep Apnea Linked to Heart Failure in Men, But Not Women

July 14, 2010

July 14, 2010 (Boston, Massachusetts) — The first prospective study to examine whether obstructive sleep apnea is associated with heart failure has found that there is a link, particularly in men, with those affected the most severely having an almost 60% increased risk of developing HF [1]. A "modest" association between sleep apnea and incident coronary heart disease (CHD) was also seen in men, but was much weaker than that reported for previous studies, the researchers say.

The trial, known as the Sleep Heart Health Study, is the first large community-based attempt to examine the association of sleep apnea with either CHD or heart failure and followed patients who were free of these conditions at baseline, says lead author Dr Daniel Gottlieb (Boston University School of Medicine, Boston, MA), who reports the findings with his colleagues online July 12, 2010 in Circulation. Previous work has focused more narrowly on patients receiving care at sleep clinics and has included only low numbers of women, they say.

"We found that men with obstructive sleep apnea are more likely to develop heart failure and CHD than men without sleep apnea," Gottlieb told heartwire . "The take-away from our study is that obstructive sleep apnea is a serious condition that warrants medical treatment." But many patients don't mention symptoms of obstructive sleep apnea, such as daytime sleepiness, during routine medical exams, or they don't experience any symptoms, he says, adding: "It’s important for anyone who suspects they have obstructive sleep apnea to discuss it with their primary-care physician."  

Is It Time for a Trial CPAP for the Prevention of CHD?

Gottlieb and colleagues followed 1927 men and 2495 women aged 40 or older, free of any heart problems when the study began, for a median period of 8.7 years. In the study, 24% of the men and 11% of the women had at least moderately severe obstructive sleep apnea, defined as an hourly average of 30 or more breathing interruptions causing oxygen depletion and lasting at least 10 seconds.

After adjustment for multiple risk factors, obstructive sleep apnea was a significant predictor of incident CHD (MI, revascularization procedures, or CHD death) only in men under 70 years of age (adjusted hazard ratio 1.10 per 10-unit increase in apnea-hypopnea index [AHI]), but not in older men or in women of any age.

Among men 40 to 70, those with AHI of 30 or greater were 68% more likely to develop CHD than those with AHI <5.

"The association of obstructive sleep apnea with incident coronary heart disease in this study is much weaker than that reported from previous clinic-based studies, which possibly reflects the older age of this cohort," say Gottlieb and colleagues.

Previous research has suggested an increased risk of cardiovascular-related death from sleep apnea in individuals ages 30 to 50, so the risk might be greatest at a relatively young age, they suggest.

Other possible explanations for differences include the fact that prior studies have looked at combined coronary and cerebrovascular end points, and there is evidence that sleep apnea may increase the risk of stroke more than the risk of CHD, they note.

But given this new evidence that men 40 to 70 years old with obstructive sleep apnea face a higher risk of CHD, "it’s really time for us to perform clinical trials to assess whether CHD risk can be reduced in patients with severe sleep apnea by treating the apnea,” Gottlieb says. The most common treatment, called continuous positive airway pressure (CPAP), involves the use of a machine that forces air into the airways to prevent breathing interruptions.

Further Study Needed on Sleep Apnea/Heart Disease Link in Women

Obstructive sleep apnea also predicted incident HF in men but not in women (adjusted HR 1.13 per 10-unit increase in AHI). Men with AHI of 30 or greater were 58% more likely to develop HF than those with AHI <5.

The fact that this increased risk of HF and the weaker link with CHD was seen in men but not in women is a "striking feature" of this study, given that it is one of the first to include a lot of women, say the researchers.

The fact that women are only about half as likely as men to have sleep apnea might make it more difficult to detect any apnea-heart disease link, they note. Also, sleep apnea tends to manifest at older ages in women than in men, they add, and there could be physiologic differences between the sexes that explain the findings.

"It is unclear whether there is a true difference in the effect of obstructive sleep apnea on men vs women, or whether we simply did not have enough women in our study with severe sleep apnea--this is an area that will require further study," Gottlieb said.

Gottlieb does not report any conflicts of interest. Disclosures for the coauthors are listed in the paper.

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