Patterns: Sleeping Through the Danger

By ERIC NAGOURNEY

Published: March 29, 2005

For most people, the hours just after rising, from 6 a.m. to noon, are the most likely times for heart attacks, while the sleeping hours are the safest.

But for the millions of people who have obstructive sleep apnea, a breathing disorder, heart attacks are much more likely in the sleeping hours, a new study finds.

Researchers from the Mayo Clinic say that for reasons that are unclear, people with the disorder are much more likely to have heart attacks from 10 p.m. to 6 a.m.

The study, which appeared last week in The New England Journal of Medicine, was led by Dr. Apoor S. Gami.

For people who have sleep apnea, the likelihood of heart attacks' occurring in the sleeping hours makes sense, given the tremendous stresses the disorder places on the body, said Dr. Virend K. Somers, a co-author of the study.

People with sleep apnea may be wrenched awake hundreds of times a night - often without their knowledge - when their airways collapse and they stop breathing.

Although the disorder has not been proved to increase the risk of heart attacks, it is suspected of doing so, and it has been linked to high blood pressure.

Dr. Somers said he believed that effective treatment for sleep apnea would reduce that patient's risk for a heart attack.

The problem, he said, is that so many people do not realize they have the disorder. (Snoring is often a symptom.)

"The vast majority of sleep apnics are still not diagnosed or treated," he said.