Snoring may warn of serious problem
If you snore, but have never mentioned the problem to a doctor, it’s time to wake up. You may suffer from sleep apnea, which mounting evidence suggests can have serious effects on health, especially the heart.
“Apnea” refers to any interruption of normal breathing. Overweight people often experience these brief interruptions while they sleep because flabby throat tissue narrows their airways, interfering with the flow of oxygen. But apnea can occur in trim people too. For unknown reasons, the tongue and throat muscles relax and sag during sleep, choking airflow and producing the familiar grating sound, which is caused by vibrating tissue in the airway.
Some people snore, but don’t experience apnea. However, if a frustrated bed partner has complained about the din you produce at night and you feel sleepy during the day, it could be that brief periods of oxygen starvation are robbing you of deep, restful slumber.
About 18 million Americans have sleep apnea, which is diagnosed in men twice as often as women, although experts suspect that most people never discuss the condition with a physician.
Sleep apnea was first identified in the 1960s, and scientists have since produced convincing evidence that the condition raises blood pressure. For example, a 2000 study in the New England Journal of Medicine found that patients with serious sleep apnea had nearly three times the risk for developing hypertension as did sound sleepers. Other studies have shown that when patients receive treatment to reduce or eliminate the breathing disruptions, their blood pressure drops.
Researchers are beginning to investigate how apnea does its damage. Peretz Lavie, a sleep-disorder expert at the Technion-Israel Institute of Technology in Haifa, has studied white blood cells from apnea patients, placing them in petri dishes with endothelial cells, which line arteries.
“The cells of the sleep-apnea patients attack the endothelial cells,” Lavie said, and this results in damage that could lead to clogged arteries. White blood cells from normal sleepers don’t behave in this destructive manner.
A study by researchers at the University of Wisconsin-Madison published this month in the American Journal of Respiratory and Critical Care Medicine also found evidence of damage to endothelial tissue in a group of more than 1,000 older apnea patients. Epidemiologist F. Javier Nieto, who led the study, hopes these findings will help convince skeptics who question whether apnea causes hypertension.
Doubters point out that apnea patients are often obese, which is itself associated with high blood pressure. “But you can turn that around and ask why obese people tend to have hypertension,” says Nieto. “Apnea may be one reason.”
However, heart disease isn’t the only health threat linked to sleep apnea. At least four studies have found unusually high rates of apnea among stroke victims. Another study, published last fall, showed that depression sufferers were five times more likely to have sleep apnea than those who weren’t depressed.
Doctors who treat sleep problems encourage apnea patients to shed pounds if they’re overweight, but most people with this breathing disorder require some form of treatment. Surgery, oral appliances and even electrical stimulation of the tongue have been used to relieve apnea, with varying degrees of success. But the gold standard of therapy remains continuous positive airway pressure, in which machines pump oxygen into the nose through a mask worn during sleep.
Researchers hope one day to produce a pill that can open blocked airways in apnea patients. One potential therapy would target the neurotransmitter serotonin, which is better known for its role in mood regulation.
Scientists know that nerves throughout the body have receptors that are stimulated by serotonin. David Carley, a sleep researcher for the University of Illinois at Chicago says one cause of sleep apnea may be that muscles in the airway close when they overreact to trivial occurrences, such as a trickle of saliva from the mouth, because their nerve receptors are overstimulated. “The culprit could be too much serotonin hanging around,” he says.
Last summer, Carley and a colleague presented a study at a sleep-medicine conference showing that apnea patients treated with an antidepressant called Remeron -- which blocks the action of serotonin -- slept more soundly and reduced their usual number of breathing interruptions by half. Carley cautions that more research is needed. But he’s optimistic a drug that can reduce breathing problems during sleep may be available within five years.
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Timothy Gower can be reached by e-mail at tgower@comcast.net. The Healthy Man runs the second Monday of the month.
