There's a good way to prevent cardiac arrest during vigorous exercise, a new study finds: Get plenty of vigorous exercise.
The 12-year study of thousands of male physicians showed that men who exercised at least five times a week had a much lower risk of sudden death about sevenfold less than those who only exercised once a week, said Dr. Christine Albert, a cardiologist and a researcher at Brigham and Women's Hospital.
Cardiologist Dr. Daniel Shindler called the finding by researchers at three Boston hospitals and the Harvard and University of Miami public health schools important.
"If you're constantly exercising not one of those weekend warriors (the study shows) you have a much better outcome," said Shindler, an associate professor at Robert Wood Johnson Medical School in New Brunswick, N.J.
Sudden cardiac arrest, generally caused by heart attacks or rhythm disturbances, kills an estimated 225,000 Americans each year.
Most, but not all, past studies have found that exercise reduces risk of sudden cardiac death. In the new study, habitual exercise did not cut the doctors' overall risk of sudden cardiac death, just the risk during exertion.
Doctors said any activities that work up a sweat, like brisk walks or gardening, can count as exercise. Besides protecting the heart, regular, vigorous exercise strengthens bones and muscles, increases flexibility, and reduces blood pressure, cholesterol, body fat, stress and risk of stroke.
The doctors warned that strenuous exercise can still pose short-term danger, at least for sedentary people, and there have been well-publicized deaths of athletes while playing and out-of-shape seniors while shoveling snow. But the risk of fatal cardiac arrest during or right after exertion is still extremely low, they said.
The study appears in today's edition of the New England Journal of Medicine.