The snoring and breathing disturbances of sleep apnoea 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 apnoea and coronary heart disease in women, or in men older than 70.
"The key here is that there is a lot of undiagnosed sleep apnoea, and that, at least in men, it is associated with the development of coronary heart disease and heart failure. Only about 10% of sleep apnoea 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 apnoea because the participants were drawn from a broad community-based population.
According to background information in the study, sleep apnoea 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 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 apnoea as calibrated on the Apnoea-Hypopnea Index.
About half had no symptoms of sleep apnoea, 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 apnoea were 68% more likely to develop heart disease, and 58% more likely to develop heart failure, than those without the condition. Increasing severity of sleep apnoea was also associated with obesity, high blood pressure, hypertension and diabetes, all of which are known contributors to heart disease.
According to the US National Institutes of Health, approximately 14 million Americans suffer from coronary heart disease, the most common cause of death in the United States.
Greater awareness needed
Dr Jordan S. Josephson, a sinus, snoring and sleep apnoea 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 apnoea." He believes that sleep apnoea, 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% of men and 9% 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 apnoea 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 apnoea is "unfortunate."
"The study suggests that sleep apnoea, 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.
Do not ignore apnoea
Treatment for the condition sometimes involves a simple surgical procedure, but many people with sleep apnoea 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 apnoea do not receive any treatment, Quan said, because it is often not recognised 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 apnoea.
"The take-home message is that if you know you snore or have sleep apnoea, 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. - (HealthDay News, July 2010)