MONDAY, July 12 (HealthDay News) -- The snoring and breathing disturbances of sleep apnea may be more than just a nuisance, with a new study linking the condition to higher risks for heart failure and heart disease in middle-aged and older men.

However, the study found no correlation between sleep apnea and coronary heart disease in women, or in men older than 70.

"The key here is that there is a lot of undiagnosed sleep apnea, and that, at least in men, it is associated with the development of coronary heart disease and heart failure. Only about 10 percent of sleep apnea cases are diagnosed, " said Dr. Daniel Gottlieb, associate professor of medicine, Boston University School of Medicine.

Gottlieb noted that while the jump in heart risk was noteworthy, it was not as large as that seen in previous clinic-based studies of sleep apnea because the participants were drawn from a broad community-based population.

According to background information in the study, sleep apnea sufferers awaken suddenly during the night struggling to breathe, often experiencing a shot of blood pressure- raising adrenaline. Most often, they go right back to sleep, unaware of what happened. But the awakenings are repeated, sometimes up to 30 times an hour, depriving the sufferer of vital oxygen and sound sleep.

The research is published online July 12 in Circulation.

In the study, almost 2,000 men and about 2,500 women -- all free of heart problems at the beginning of the research -- were recorded as they slept using polysomnograms, which measured the presence and severity of sleep apnea as calibrated on the Apnea-Hypopnea Index.

About half had no symptoms of sleep apnea, the team found, while half had mild, moderate or severe symptoms.

Participants were then contacted at various times from 1998 to the final follow-up in April 2006. During that time, 473 cardiac events occurred, including 185 heart attacks, 212 heart bypass operations, and 76 deaths. There were also 308 cases of heart failure; of these 144 people also had a heart attack.

The study found that men between 40 and 70 years of age who had severe sleep apnea were 68 percent more likely to develop heart disease, and 58 percent more likely to develop heart failure, than those without the condition. Increasing severity of sleep apnea was also associated with obesity, high blood pressure, hypertension and diabetes, all of which are known contributors to heart disease.

According to the U.S. National Institutes of Health, approximately 14 million Americans suffer from coronary heart disease, the most common cause of death in the United States.

Dr. Jordan S. Josephson, a sinus, snoring and sleep apnea specialist at Lenox Hill Hospital in New York City, said the study is important because "it brings a greater awareness to the public about sleep apnea." He believes that sleep apnea, linked to heart disease through this and other studies, may be an indirect factor in many heart deaths.

Experts estimate that the condition affects 24 percent of men and 9 percent of women, but Josephson believes the numbers are actually higher because people don't know they have a problem unless a partner or spouse tells them they snore.

"Sleep apnea is [also] the number one medical cause for divorce and the ending of partnerships," added Josephson, because many couples end up sleeping apart, not sleeping well, and not functioning well during the day.

Dr. Stuart Fun Quan, another of the study's authors, agreed that the under-diagnosis of sleep apnea is "unfortunate."

"The study suggests that sleep apnea, at least in men, is a potentially remediable cause of coronary heart disease and heart failure," said Quan, a professor of medicine at Harvard Medical School, Boston.

Treatment for the condition sometimes involves a simple surgical procedure, but many people with sleep apnea opt for a mask at night connected to a Continuous Positive Air Pressure (CPAP) machine that pumps oxygen into the blood. But many with sleep apnea do not receive any treatment, Quan said, because it is often not recognized as a serious condition.

Josephson -- who believes that even plain old snoring constitutes an oxygen-depleting stress on the heart -- sounded the alarm for those who would ignore sleep apnea.

"The take-home message is that if you know you snore or have sleep apnea, or someone tells you (that) you snore, you have to go to a specialist to make the correct diagnosis," said Josephson, adding that it's vital to get treatment.

More information

Find out more about sleep apnea at the U.S. National Heart, Lung, and Blood Institute.