Sleep apnea a risk for heart disease, stroke

NEW YORK (Reuters Health) - A growing number of studies suggest that the nighttime breathing disorder, sleep apnea, can contribute to a range of cardiovascular diseases, according to researchers from the Mayo Clinic in Rochester, Minnesota.

Writing in the journal Sleep, they detail the evidence linking sleep apnea to high blood pressure, coronary artery disease, stroke, heart failure and heart-rhythm disorders.

The connection between the sleep disorder and heart health is increasingly being recognized, the authors say -- both because of recent research, and possibly because sleep apnea is becoming more common.

People with sleep apnea have repeated stops and starts in their breathing as they sleep, sometimes hundreds of times per night. Of the two forms of sleep apnea, obstructive sleep apnea (OSA) is by far the more common; it occurs when the soft tissues at the back of the throat repeatedly collapse during sleep, temporarily cutting off breathing. When this happens, the brain briefly rouses the person from deep sleep to re-open the airways.

Sleep apnea sufferers often don't remember these awakenings, but some tell-tale signs of the disorder include chronic, loud snoring and daytime drowsiness.

Sleep apnea does more than interrupt a good night's rest, however. Growing evidence is implicating it as a risk factor for numerous cardiovascular problems, according to the authors of the new report, led by Dr. Sean M. Caples.

The short-term consequences of sleep apnea episodes include oxygen deprivation, nervous system activation and changes in pressure within the chest, according to the researchers.

Over time, they explain, these stressors can cause long-term dysfunction in the nervous and cardiovascular systems, ultimately contributing to high blood pressure, heart problems and stroke.

The strongest connection has been seen between OSA and high blood pressure. Repeated episodes of oxygen deprivation seem not only to trigger short-term spikes in blood pressure, the researchers note, but may also lead to chronic blood pressure elevations.

Recent studies have also strengthened the connection between OSA and coronary artery disease, heart attack and stroke, according to Caples and his colleagues. In addition, although the evidence is less clear, research is implicating OSA in heart rhythm disorders and heart failure.

"There are mounting data suggesting a potentially important causative role of OSA in cardiovascular disease, particularly systemic hypertension (high blood pressure)," the report's authors write.

More studies are needed to solidify the connections between sleep apnea and certain other forms of cardiovascular disease, they say. "Perhaps more importantly," they add, researchers need to find out whether treating sleep apnea lowers the odds of cardiovascular problems.

SOURCE: Sleep, March 1, 2007.