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By Joyce Frieden
BETHESDA, Md., Mar 28 (Reuters Health) - When it comes to finding the underlying cause of heart disease, high blood pressure or other heart problems, doctors may want to consider the possibility of sleep apnea, a Minnesota doctor said on Wednesday at a conference on mind-body medicine held at the National Institutes of Health.
People with sleep apnea often snore loudly and have many episodes each night in which they stop breathing and then snort and gasp for breath--often without waking completely. These episodes strain the cardiovascular system and can cause an increase in blood pressure.
"Physicians should look for sleep disorders in patients with congestive heart failure or hypertension, especially if they are not responding to standard therapy," Dr. Virend Somers told Reuters Health. "Unfortunately, doctors who are trying to understand and treat disease are focused mainly on wakefulness."
Compared to people without sleep apnea, studies have shown that "patients who have sleep apnea and normal blood pressure are more likely to develop hypertension within 4 years," said Somers, who is professor of hypertension and cardiology at the Mayo Clinic in Rochester, Minnesota. The findings suggest that sleep apnea may cause chronic high blood pressure, also known as hypertension.
In studies performed on patients with sleep apnea and no other illnesses, Somers and colleagues found that the sleep apnea patients had higher sympathetic nervous system activity during both sleep and waking periods, compared with another group of individuals who were matched for age, gender and body mass index. The sympathetic nervous system controls involuntary functions such as heart rate and blood vessel constriction.
In people without sleep apnea, sympathetic nervous activity tends to decrease during sleep and blood pressure falls, Somers said.
"But with apnea, patients stop breathing, their oxygen levels go down and their carbon dioxide levels go up, resulting in activation of the sympathetic nervous system. (Then) when apnea subjects breathe in, their cardiac output increases and their blood pressure skyrockets, disrupting the normal regulation of the sympathetic activity and blood pressure that we would expect through the night."
Apnea patients also have less variation in heart rate along with their greater variability in blood pressure, Somers noted.
"Both of these things are bad and can predict cardiovascular disease down the road." he said.
These patients also have higher levels of endothelin, a potent blood vessel-constricting compound produced by the body.
Many of the sleep apnea patients' problems can be helped with the use of a continuous positive airway pressure device, which delivers a stream of air into the nasal passages via a mask. This standard treatment for the sleep disorder can help keep the airway clear during sleep, and reduce episodes of apnea.
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