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Study Assesses Risks of Exercise-Related Sudden Death

Health: Scientists say men face significantly higher danger during or just after workouts--but not as great as the perils of failing to engage in regular physical activity.


The risk of dropping dead of a heart attack is significantly raised during a bout of vigorous exercise or shortly after it, according to one of the largest studies investigating such exercise-related sudden death.

But that's no excuse for being a couch potato. Experts stress that the risk, though heightened, is still tiny--and it is far outweighed by the benefits of regular exercise on overall health and longevity.

The study, published in today's New England Journal of Medicine, underscores the importance of exercising regularly instead of sitting on one's rump for days and weeks at a time, then charging onto the racquetball court.

For such "weekend warriors," the risk of exercise-related sudden death was considerably higher than it was for those who worked up a sweat several times a week, the study found.

Heart disease--often undiagnosed--is the primary cause of such sudden deaths in the middle-age population that was studied. Because of this, experts say, it is important to start slow and get checked out by a doctor if you're older than 40, have risk factors for heart disease and are sedentary but want to turn over a new leaf.

"The public should not be alarmed by this--it's just a warning to be careful," said Dr. Gerald Fletcher, a cardiologist at the Mayo Clinic in Jacksonville, Fla., and a spokesman for the American Heart Assn.

Prior studies and occasional high-profile deaths of young athletes, among others, have indicated that strenuous exercise carries some risk to the heart.

The present study involved more than 21,000 physicians ages 40 to 84, none of whom had any history of heart problems and who were tracked for many years.

At the study's start, the men completed a questionnaire describing how many times a week they exercised vigorously enough to work up a sweat. Twelve years later, records revealed that 122 of them had died suddenly from heart-related causes--23 of them while engaged in strenuous exercise or within half an hour after it.

That number--23--was greater than would be expected from random chance, the scientists reported. This suggests that strenuous exercise really does impart some immediate, measurable risk. In fact, the scientists estimate that the risk of sudden death during or right after vigorous exercise was nearly 17 times higher than it was for a comparable period of time spent at leisure.

It's still extremely small, though: just one extra death for every 1.51 million bouts of physical activity.

"To me, one chance in 1.5 million is very low risk--if you exercised every day for a million and a half days, that's still 4,110 years," said Dr. Allan Abbott, professor of family medicine at Keck School of Medicine at USC.

The level of risk depends on who you are: Men who had reported exercising regularly were less likely to die of sudden death during exercise than those who had reported exercising infrequently.

This makes sense, experts said. Exercise conditions the heart, reducing the strain imposed by exercise. For instance, among the Masai, an East African tribe that Abbott studies, people commonly walk 15 miles daily, and their hearts are bigger and stronger and have better blood-pumping capacity as a consequence.

And there is overwhelming evidence that regular exercise reduces blood pressure and favorably alters blood lipids, thus helping to ward off heart disease--a thickening of the walls of the blood vessels supplying the heart.

Such heart disease is the typical cause of exercise-related sudden death in middle-age men. (In young athletes, in contrast, an underlying congenital heart abnormality is usually the cause.) Sudden death can occur when a piece of thickened wall, known as plaque, tears during the extra exertion, blocking the coronary artery and cutting off blood to the heart, which then goes into spasm.

The study probably holds true for many American men, Fletcher said.

"These physicians were probably pretty typical professionals: working five to 5 1/2 days, no time during the week and then they get out on the weekend, go kayaking, deciding to run, do their weights--that's not healthy," he said. Neither, he added, is it healthy when normally sedentary men shovel snow from their driveways, an activity that is very hard on the heart.

The study was led by Dr. Christine Albert, a cardiologist at Massachusetts General Hospital and a researcher at Brigham and Women's Hospital in Boston.

Albert and her co-workers point out that the study, though large, has limitations. Since it was a study only of men, it is not known if the same findings would hold for women. Also, the measure of people's exercise levels was limited, since data were gathered by questionnaire and only at the start of the study.

The researchers also stress that the risk of exercise-related sudden death is much smaller than the risk of a sedentary lifestyle.

"Even though there's this small increase in risk, it shouldn't cause anyone not to want to participate in exercise--but it should point out that if you're going to begin an exercise program, start slowly," said Albert.

The American Heart Assn. recommends that people exercise for 30 to 60 minutes four to six days a week, Fletcher said. Though moderate exercise also is beneficial, ideally some of that exercise should be vigorous--walking a treadmill at 4 mph, for instance--if the exerciser is in good enough condition.

Experts also recommend that people who are in their 40s or older consult with their doctors before starting an exercise program, especially if they have any risk factors for heart disease. People with angina or high blood pressure or those who have had a heart attack should take special care.

About 500,000 people die of heart attacks every year in the U.S. Half of those die suddenly, without warning.

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