Two studies in the current issue of the New England Journal of Medicine 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 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, 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, according to Somers. 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.
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," stresses Somers, adding that the CPAP device was intended to treat obstructive sleep apnea, not 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.