Sleep Apnea Can Cause Strokes
Disorder More Than Doubles Risks, Yale Researchers Say; Tape-Recording Your Sleep
By ROBERT TOMSHO
Searching for the causes of deadly strokes, medical researchers say they have identified a culprit in the bedroom: sleep apnea.
The disorder, often undiagnosed for years, causes sleeping people to temporarily stop breathing. A number of studies have found links between sleep apnea and serious cardiovascular disease. But it wasn't clear whether sleep apnea actually led to strokes.
Now a Yale University study published in this week's New England Journal of Medicine singles out the condition as a cause of strokes. The study, which involved 1,022 patients over the age of 50, found that the most common form -- so-called obstructive sleep apnea -- more than doubles the chances of a stroke or death. The Yale study also found that severe cases of obstructive sleep apnea can more than triple the risk of stroke or death.
H. Klar Yaggi, the study's principal investigator and a sleep-medicine specialist at the Yale University School of Medicine, says the higher incidence of stroke and death remained even after researchers adjusted for other traditional stroke-risk factors such as diabetes, hypertension and obesity.
The results bolster other recent findings, including a study by University of Toronto researchers earlier this year indicating that patients with severe sleep apnea were as many as four times as likely to suffer strokes. Strokes are the third leading cause of death in the U.S. after heart disease and cancer, striking 700,000 people a year and killing 163,000 of them.
An estimated one in five American adults suffers from at least mild forms of sleep apnea, although physicians generally say treatment isn't necessary unless it involves five or more pauses in breathing per hour of sleep, along with other symptoms such as daytime drowsiness. Roughly 4% of adult American men and 2% of women suffer from the disorder to that degree, according to a study at the University of Wisconsin. But some researchers estimate that more than half of these cases go undiagnosed.
With obstructive sleep apnea, the lungs continue to work but the muscles in the throat become so relaxed that the airway becomes all or partially closed. With central sleep apnea, a far rarer form, the body temporarily stops making any effort to breathe.
Common symptoms include loud snoring, choking or gasping during sleep and daytime drowsiness, although the apnea episodes often fail to actually wake the sufferers. The disease often strikes those who have hypertension or are overweight. A 2003 study of 300 National Football League players found that 14% of them had sleep apnea, and the disease is believed to have played a role in the sudden death in 2004 of former Green Bay Packer great Reggie White.
Sleep apnea is also associated with diabetes, hypertension and driving accidents, according to the National Institutes of Health. Treatments include a mask-like device that is worn over the nose and mouth during sleep. The device is attached to a pump that pushes air through the mask to keep the upper air passage open.
One big question raised by the Yale study, however, is whether treating sleep apnea will reduce the incidence of strokes.
All 1,022 patients involved in the study had been referred to the Yale Center for Sleep Medicine for various sleep problems. Of them, 697 were diagnosed with obstructive sleep apnea and 325 had other disorders. Researchers followed up on patient outcomes for an average of about three years after the initial diagnosis.
Of the 88 incidences of strokes or death subsequently recorded, 72 occurred among the sleep-apnea patients. Many of these patients were undergoing various forms of treatment, including the pump-and-mask apparatus known as continuous positive airway pressure, or CPAP. But even with treatment, the group still had an elevated risk of stroke and death, according to the study, which was paid for by grants from the NIH, the Department of Veterans Affairs and Yale.
To some in the sleep-medicine field, that points the way to the next generation of related research. "Now what we need to know is that treating that sleep apnea decreases the stroke risk substantially," says Virend Somers, a cardiologist at the Mayo Clinic in Rochester, Minn., who wasn't involved with the Yale study. "We don't have an absolute cast-iron, randomized study to show that."
A separate study in the New England Journal of Medicine, by researchers at the University of Toronto, found that CPAP therapy didn't improve the survival rates of patients suffering from both central sleep apnea and heart failure.
Some patients do report finding relief from treatment. John Thompson, a 52-year-old former chef from New Haven, Conn., said his heavy snoring woke his wife up for years. He didn't know he had obstructive sleep apnea until a little over a year ago, when the cardiologist who was treating him for chest pains sent him to the Yale Center for Sleep Medicine for an assessment. There, doctors monitored his sleeping with cameras and electronic sensors attached to various parts of his body.
These days, Mr. Thompson, who wasn't part of the Yale study, sleeps wearing a CPAP device and says he is better-rested and has more energy. "Now I can walk further," he says. "At one point, I couldn't walk two feet."
Some researchers advise people to seek a doctor's help if their sleep partners notice that they stop breathing repeatedly during the night. For those who live alone, symptoms to watch for include difficulty concentrating, mood swings and falling asleep at inappropriate times during the day. Another strategy: Turn on a tape recorder at night and listen to how you breathe while sleeping.
"The public-health message here is that we need to continue to work on timely diagnosis and timely initiation of treatment of people with symptomatic sleep apnea," says Carl Hunt, director of the National Center on Sleep Disorders Research, part of the NIH that helped pay for the Yale study.
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