Stroke victims who have obstructive sleep apnea die sooner than stroke victims who do not have sleep apnea or who have central sleep apnea, according to Swedish researchers, who will present their findings at the American Thoracic Society's 2008 International Conference in Toronto on May 19.
The researchers followed 132 stroke patients over 10 years. Twenty-three of those patients had obstructive sleep apnea; 28 of those patients had central sleep apnea. Those with an obstructive apnea-hypopnea index of 15 or greater were 76 percent more likely to die earlier. Those with a lower apena-hypopnea index of 10 were also at greater risk of early death.
"The findings are particularly interesting because obstructive sleep apnea is a treatable condition," said Karl Franklin, M.D., who led the research team at University Hospital in Umea, Sweden.
The researchers' results were independent of age, gender, smoking, body-mass index, hypertension, diabetes, atrial fibrillation, cognitive ability and how dependent patients were on help in their daily lives.
According to Dr. Franklin, patients with central sleep apnea tended to have an increased risk of earlier death, but unlike those with obstructive sleep apnea, that risk was not independent of confounders.
Earlier research Dr. Franklin and his colleagues conducted using trans-cranial Doppler found that cerebral blood flow and arterial blood pressure increase during obstructive apneas and then rapidly decrease to low values when the apnea ends. This pattern, the researchers said, suggests cerebral ischemia occurs at the same time as oxygen saturation is low.
The findings of their latest study, Dr. Franklin noted, indicate the importance of a clinical trial for stroke patients with obstructive sleep apnea to see whether treating the sleep disorder will extend their lives.
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