After studying the sleep characteristics of nearly 11,000 adults in an overnight sleep laboratory, Mayo Clinic researchers suggest that obstructive sleep apnea (OSA) - and, in particular, the low nighttime oxygen saturation of the blood it causes - may be a risk factor for sudden cardiac death (SCD).
OSA is a condition that disrupts breathing during sleep and is associated with obesity.
The study identified OSA as one of two traits that contribute to the highest risk of SCD. The other is age - patients who are 60 years old or older.
SCD can happen when the heart's electrical system malfunctions; if treatment - cardiopulmonary resuscitation and defibrillation - is not administered quickly, a person dies.
If further studies validate these findings, OSA would join established risk factors such as smoking, obesity, high cholesterol and high blood pressure. Mayo Clinic cardiologist Apoor Gami, M.D., the lead researcher on the study, presents the findings today at the American Heart Association's Scientific Sessions 2008 in New Orleans.
Significance
Physicians have suspected for years that OSA might be implicated in SCD because of evidence that low oxygen alters the blood vessels in a way that promotes heart disease. This is the first large study to rigorously test the hypothesis, Dr. Gami says.
"Nighttime low oxygen saturation in the blood is an important complication of obstructive sleep apnea," says Virend Somers, M.D., Ph.D., the study's principal investigator. "Our data showed that an average nighttime oxygen saturation of the blood of 93 percent and lowest nighttime saturation of 78 percent strongly predicted SCD, independent of other well-established risk factors, such as high cholesterol. These findings implicate OSA, a relatively common condition, as a novel risk factor for SCD."
Dr. Somers says these early results are relevant to clinical care. He urges physicians to watch for OSA in their heart patients and consider treating severe cases. "It is possible that diagnosing and treating sleep apnea may prove to be an important opportunity to advance our efforts at preventing and treating heart disease," he says.
Obstructive sleep apnea and public health