Sleep Disorders Put Stroke, Blood Pressure Patients at Risk
MONDAY May 19, 2008 -- Two new studies give greater incentive for people with obstructive sleep apnea to seek treatment for this disorder.
In one study, Swedish researchers found that stroke victims with obstructive sleep apnea (OSA) die sooner than stroke victims who don't have the sleep disorder or another less common type of it.
The other study, done by Spanish researchers, reports that people with obstructive sleep apnea and hypertension may be able to lower their blood pressure if the breathing condition is treated with continuous positive airway pressure.
The studies were to be presented Monday at the American Thoracic Society's 2008 International Conference, in Toronto.
In obstructive sleep apnea, the brain signals throat muscles to relax to the point the airway becomes blocked. A less common form of the disorder is central sleep apnea, in which the brain fails to properly regulate the signals to the muscles that control breathing. In both cases, the person wakes in his or her effort to take in oxygen.
The Swedish study, following 132 stroke patients for a decade, found that those with an obstructive apnea-hypopnea index of 15 or greater were 76 percent more likely to die earlier than those with a less severe condition or none at all. Those with a lower apnea-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," lead researcher Dr. Karl Franklin, of the University Hospital in Umea, Sweden, said in a prepared statement.
He added that those with central sleep apnea also had an increased risk of earlier death, but unlike their counterparts with obstructive sleep apnea, that risk was not independent of variables such as age, gender, smoking, body mass index, hypertension, diabetes, atrial fibrillation, cognitive ability and how dependent patients were on help in their daily lives.
Based on these findings, Franklin said a clinical trial is needed to determine whether treating obstructive sleep apnea in stroke patients helps extend their lives.
In the Spanish study, which looked at 394 patients with high blood pressure and OSA mild enough that it did not affect their daytime alertness, those being treated with a continuous positive airway pressure (CPAP) machine over a one-year period experienced, on average, a 2mmHg drop in both systolic and diastolic blood pressure compared with those not using the machine. Use of the machine for five or more hours a night produced the greatest effect.
"This is the largest study trial in the field, and it shows that CPAP has an effect on cardiovascular outcomes regardless of symptoms," lead researcher Dr. Ferran E. Barbe said in a prepared statement. "This suggests that CPAP cannot only be used to treat the symptoms of sleep apnea (daytime sleepiness), but also to reduce cardiovascular risk in apneic patients."
However, the researchers stopped short of recommending use of the machine for all OSA patients with high blood pressure and no daytime drowsiness. Instead, they called for further study of the cardiovascular benefits.
"In the future, we would like to know the effects of CPAP treatment on other cardiovascular outcomes such as stroke, myocardial infarction or heart failure," Barbe said.
The National Institute of Neurological Disorders and Stroke has more about sleep apnea.
Posted: May 2008