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"The cardiac death peak for the general population comes just after waking, from six to noon, which for several reasons is the most vulnerable time for the heart and blood vessels."

says Virend Somers, M.D.,PhD., the Mayo Clinic cardiologist who directed the study. "Almost twice as many people die of cardiac causes then, as compared to the midnight to 6 a.m. period. But for patients with obstructive sleep apnea, the peaks were reversed; more than twice as many cardiac deaths came during the sleeping hours."

Apoor Gami, M.D., lead author of the study, examined the death certificates of 112 Minnesota residents who had sleep studies at the Mayo Clinic Sleep Disorder Center between 1987 and 2003 and who died suddenly of cardiac causes. More than half (54 percent) of the 78 OSA patients died between 10 p.m. and 6 a.m., while only 24 percent of the 34 cardiac deaths among non-OSA patients occurred during that period.

OSA is a collapse like a wet paper straw of the airway during sleep. It causes the person to stop breathing momentarily, as many as 60 times per hour. This significantly lowers oxygen levels in the bloodstream, elevates nighttime blood pressure and causes heart rhythm disturbances. Dr. Gami pointed out that about a fifth of North American adults have sleep apnea; most remain undiagnosed.

Snoring is often a symptom, as is inability to stay awake during the day. The standard treatment is continuous positive airway pressure (CPAP), a mask worn at night to keep the airway open.

Dr. Gami says the team's findings not only show that patients with OSA are at much higher risk of cardiac death during sleep; they also indicate that the 6 a.m.-noon peak of cardiac deaths in the general population is even higher for those who don't have sleep apnea. "Because so many pe
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Contact: Lee Aase
newsbureau@mayo.edu
507-284-5005
Mayo Clinic
23-Mar-2005