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Association noted between sleep apnea and cardiovascular disease
By Mayo Clinic,
Nov 10, 2005 - 5:42:38 PM
In the current issue of the New England Journal of Medicine, two studies draw attention to the newly recognized association between sleep disorders and heart trouble. The relevance of these studies to patients with sleep apnea is discussed in an accompanying editorial by Virend Somers, M.D., Ph.D., a Mayo Clinic cardiologist.
The first study, on the use of continuous positive airway pressure (CPAP) for patients with central sleep apnea and heart failure, was led by T. Douglas Bradley, M.D., of Toronto General Hospital. The other study on obstructive sleep apnea as a risk factor for stroke and death was led by H. Klar Yaggi, M.D., of Yale Center for Sleep Medicine.
In his editorial, Dr. Somers notes that central sleep apnea is characterized by intermittent loss of respiratory drive, while obstructive sleep apnea results in a narrowing or collapse of the airway. While they differ, both sleep apneas are "linked to the modern-day epidemics of obesity, cardiovascular disease, and heart failure," he says.
The results of the first study -- also referred to as the Canadian Positive Airway Pressure trial -- were disappointing because, even though the treatment was carefully applied, it was not sufficiently effective, Dr. Somers says. Patients with both heart failure and central sleep apnea received either CPAP -- a mask worn during sleep that delivers air through the airway -- or no treatment to see if CPAP improved survival.
In the end, mortality was similar in both groups. "Unfortunately, the study doesn't tell us for certain whether or not we should treat central sleep apnea in our heart failure patients," Dr. Somers says.
Because of limited effectiveness of the treatment, the study points to a need to "rethink what we are treating and how we are treating it," he says, adding that the CPAP device was intended to treat obstructive sleep apnea, not central sleep apnea. "This suggests we need to find better treatments and devices for central sleep apnea."
The second study provides strong support that obstructive sleep apnea is likely involved in causing strokes, transient ischemic attack or sudden death, he says.
The troubling part of this study is that most people in it were already receiving treatment for obstructive sleep apnea, Dr. Somers says. "So is the stroke risk even higher for people not being treated, and how much do patients benefit from treatment?" he asks.
The goal for treating sleep apnea -- central and obstructive -- is to enable patients to be less sleepy, feel better and live longer, he says. He believes treatment is important because he has seen many patients, especially those with heart disease, do well with effective treatment, which can reduce sleepiness and lower blood pressure. However, Dr. Somers cautions that it remains to be proven that treating sleep apnea prevents deaths from heart disease.
These studies remind us to consider how and why we are treating sleep apnea in our heart disease patients, he says.
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