NEW YORK (Reuters Health) – Obstructive sleep apnea is a risk factor for early death in patients who have had a stroke, according to findings published in the February 11th issue of the Archives of Internal Medicine.

"Sleep apnea occurs frequently among patients with stroke, but it is still unknown whether a diagnosis of sleep apnea is an independent risk factor for mortality," Dr. Karl A. Franklin, of Umea University Hospital, Sweden, and colleagues write.

To better understand this relationship, the researchers examined whether obstructive or central sleep apnea reduced long-term survival among 132 stroke patients admitted for in-hospital stroke rehabilitation between April 1, 1995, and May 1, 1997.

All of the subjects underwent overnight sleep apnea recordings at a mean of 23 days after the stroke onset and were followed for a mean of 10 years. The primary outcome was death; no patients were lost to follow-up.

The team defined obstructive sleep apnea as an obstructive apnea-hypopnea index of 15 or greater; central sleep apnea was defined as a central apnea-hypopnea index of 15 or greater. Patients with obstructive or central apnea-hypopnea with indexes of less than 15 served as controls.

The authors report that 23 patients (17.4%) had obstructive sleep apnea and 28 patients (21.2%) had central sleep apnea during Cheyne-Stokes respiration. Two patients who had both obstructive and central sleep apnea were excluded. A total of 79 patients served as controls.

Of the 132 patients, 116 (87.9%) had died at follow-up, which included all of the patients with obstructive sleep apnea, 96.4% of those with central sleep apnea, and 81.0% of controls.

The mortality rates of patients with obstructive sleep apnea were significantly greater than that of the controls (adjusted hazard ratio, 1.76; p = 0.03), independent of age, sex, body mass index, smoking, hypertension, diabetes, atrial fibrillation, and other variables. Central sleep apnea was not associated with increased mortality (adjusted hazard ratio, p = 0.80).

"Possible mechanisms causing increased mortality among patients who experience stroke and who have sleep apnea include nocturnal hypoxemia and an increase in the risk of sudden cardiovascular death during sleep," Dr. Franklin’s team suggests.

Arch Intern Med 2008:168:297-301.

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