Exercise cuts risk of sudden cardiac death

Exercise improves your health, but can you kill yourself with too much snow shoveling, yard work, jogging, or playing tennis?

“Despite all of the known benefits of exercise, there are also well-documented associations between acute episodes of exertion and sudden cardiac death,” notes Christine Albert, an assistant professor of medicine at Harvard Medical School. “Although relatively rare, these deaths commonly occur in an unexpected fashion among those who appear quite healthy.”

In the largest study ever done to get a better handle on this question, Albert and her colleagues followed the exertions of almost 85,000 women for 24 years, while keeping track of their hearts. The women, selected from an ongoing study of registered nurses known as the Nurses Health Study, were between 34 and 59 years old in 1986. From then until 2004, the women filled out questionnaires about how much time they spent jogging, running, bicycling, swimming, playing tennis or squash, and undertaking other activities that require moderate to vigorous exertion.

“To our knowledge, this analysis is the first to assess both the transient and long-term risk of sudden cardiac death associated with physical activity among women,” says Albert, senior author of the study and also director of the Center for Arrhythmia Prevention at the Harvard-affiliated Brigham and Women’s Hospital in Boston. Results of the study appeared in the March 22/29, 2006 Journal of the American Medical Association’s theme issue on Women’s Health.

The findings are encouraging. Out of almost 85,000 women, only nine died while doing yard work, housework, swimming, or physical therapy. To put this in numbers, as scientists always like to do: Their investigation covered 1.93 million person years of exercise and recorded only one death for each 36.5 million hours of exertion. In other words: Sudden cardiac death during exertion is an extremely rare event in women.

And there’s still more good news. Regular exercise may significantly minimize this small risk, in both the short and long term.