Study helps explain connection between sleep apnea, stroke...( BETHESDA Md. (Jan. 6 2009) − ...)

BETHESDA, Md. (Jan. 6, 2009) − Obstructive sleep apnea decreases blood flow to the brain, elevates blood pressure within the brain and eventually harms the brain's ability to modulate these changes and prevent damage to itself, according to a new study published by The American Physiological Society. The findings may help explain why people with sleep apnea are more likely to suffer strokes and to die in their sleep.

Sleep apnea is the most commonly diagnosed condition amongst sleep-related breathing disorders and can lead to debilitating and sometimes fatal consequences for the 18 million Americans who have been diagnosed with the disorder. This study identifies a mechanism behind stroke in these patients.

The study, "Impaired cerebral autoregulation in obstructive sleep apnea" was carried out by Fred Urbano, Francoise Roux, Joseph Schindler and Vahid Mohsenin, all of the Yale University School of Medicine in New Haven, Connecticut. It appears in the current issue of the Journal of Applied Physiology.

During sleep apnea episodes, the upper airway becomes blocked, hindering or stopping breathing and causing blood oxygen levels to drop and blood pressure to rise. The person eventually awakens and begins breathing, restoring normal blood oxygen and blood flow to the brain.

Ordinarily, the brain regulates its blood flow to meet its own metabolic needs, even in the face of changes in blood pressure -- a process known as cerebral autoregulation. This study found that the repeated surges and drops in blood pressure and blood flow during numerous apnea episodes each night reduces the brain's ability to regulate these functions.

Up to 4% of the population suffers from obstructive sleep apnea. In a previous study, Dr. Mohsenin and his colleagues showed that people with sleep apnea are three times more likely to suffer a stroke or die, compared to people in a similar st
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