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, U.S. researchers reported on Wednesday.
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 suffer from some degree of apnea, where the throat repeatedly closes during sleep, causing breathing to stop for 10 to 30 seconds during sleep 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.
Vulnerable at night
The study of 112 Minnesota residents with diagnosed sleep apnea who died suddenly from cardiac causes found they were far more likely to die between midnight and 6 a.m..
More than half died between 10 p.m. and 6 a.m. -- usually the time when people are the least likely to die of heart problems.
However, apnea sufferers were only half as likely to suffer a fatal heart attack between 6 a.m. and noon, the time when everyone else is most vulnerable.
And from noon to 6 p.m., the risk of sudden death from heart attack was only 30 percent of what it was for people without apnea.
“We didn’t show that sleep apnea increases the risk of sudden death at all. It changes the time,” Somers, a cardiologist, said in a telephone interview.
A much larger study of about 12,000 people now underway may reveal if death is more common among apnea sufferers. “In 18 months or so we should have an answer,” he said.
The new study raises several questions.
Many of the people with apnea had been given machines that use air forced through a face mask to keep the throat open. Although the death rate was higher during sleep, that does not mean the machines were not effective, Somers said.
The researchers had no way of knowing how many patients were actually using the devices, especially on the morning they died.
Generally, two in five patients don’t use their machines regularly, he said.
People may say they want to die in their sleep, Somers said, “but sleep is such a relatively passive state. If you go through all the stresses of daytime and you don’t die, why should you die at all during sleep?”
