Sleep apnea kills at night, study says

Patients with sleep apnea are more likely to die from heart attacks at night, while sleeping, than in the day, which is the time when everyone else is most vulnerable, US researchers reported yesterday.

Most heart attacks take place between dawn and noon in the United States but sleep apnea -- marked by a tendency to snore, stop breathing and then startle awake -- changes this pattern, the researchers found.

What is still not clear is how much sleep apnea raises the risk of premature death overall, the researchers wrote in this week's issue of the New England Journal of Medicine.

''Our study cannot address the question of whether obstructive sleep apnea increases the overall risk of sudden death from cardiac causes," Dr. Virend Somers of the Mayo Clinic College of Medicine in Rochester, Minn., and colleagues wrote.

As many as one in four Americans suffers from some degree of apnea, where the throat repeatedly closes during sleep, causing breathing to stop for 10 to 30 seconds and oxygen levels to fall dramatically.

The condition, more common in men and the obese, causes stress on the heart and makes people tired during the day.

The study of 112 Minnesota residents with sleep apnea who died suddenly from cardiac causes found they were far more likely to die between midnight and 6 a.m.