An exercise paradox: Risk leads to health

The deaths of two runners during last week’s Los Angeles Marathon are a sobering reminder that doing something good for yourself can sometimes have a bad outcome.

In people with heart disease -- those who know it and those who don’t -- recent studies have confirmed that exercise can indeed trigger a heart attack or sudden cardiac death. A piece of plaque can break off from an artery and stop blood flow. An irregular heartbeat can develop, slowing blood flow to the brain. Or blood pressure can increase to the point of placing a dangerous strain on the heart.

It’s scary enough to make a fitness buff store those sneakers in the closet for good.

But it would be a mistake for people to equate exercise with danger, health experts say. Although working out can precipitate a heart attack or sudden death during the exertion and for about one hour afterward, regular exercise is important in preventing those events.

“The paradox is when people exercise regularly, they are protected against sudden death. But there is this real risk of sudden cardiac death during exercise,” says Dr. Christine Albert, a cardiologist at Brigham and Women’s Hospital in Boston and the author of a new study on exercise and sudden death.

In a study published last week in the Journal of the American Medical Assn., Albert and her colleagues found a slightly increased risk of sudden cardiac death in women during exercise as opposed to during other activities. But the risk of sudden death during exercise was still very low, only 1 death per 36.5 million hours of exertion. The data were collected from the Nurses’ Health Study, a long-term study of more than 121,000 women.

A similar study of men, published by Albert in 2000 in the New England Journal of Medicine, found 1 death per 1.51 million hours of exertion.

But exercisers overall are better off than their sedentary counterparts when it comes to exertion -- and everyone must sometimes engage in strenuous or moderately strenuous activity. Among typically inactive people, the risk of dying during exertion was 20.9 times higher than when doing nothing, according to a 2005 study, also drawn from the Nurses’ Health Study. The average woman was six times more likely to die during moderate-to-vigorous exercise than when sedentary. Overall, the study found that the more women exercised, the more they lowered their risk of sudden cardiac death.

“If you look at groups that exercise regularly, their risk of sudden cardiac death is much less than the sedentary population,” says Dr. William O. Roberts, an associate professor and sports medicine expert at the University of Minnesota.

Each heavy snowfall in Roberts’ part of the country provides such proof, he says. Previously couch-bound people go outside to shovel snow, and some collapse and die from the exertion.

To most people, however, those deaths aren’t as surprising as that of an apparently fit-looking individual who dies during a marathon. Doctors admit they aren’t very good at identifying who those people might be. The risk of sudden death or heart attack is higher among people with heart disease, Albert says. But 55% of people who are victims of sudden cardiac death have no history or obvious symptoms of heart disease. A heart attack, in which a blockage occurs in a major coronary artery, is different from sudden cardiac death, in which a malfunction of the heart’s electrical system causes an irregular heartbeat that causes the heart to stop beating.

“Unfortunately we can’t predict who it will happen to; that is the problem,” Albert says. “Often it happens in people who appear very healthy.”

People who are middle-aged or older and exercise or plan to start exercising can lower the odds that exertion will be deadly. The key is to identify the risk of having heart disease.

Those who have a family history of heart disease (especially heart disease that occurs at a younger age), or have any of the risk factors for heart disease, should discuss the exercise regimen with a doctor, Roberts says. Risk factors for heart disease include smoking, Type-2 diabetes, high blood pressure, high cholesterol and obesity.

“If you’re 40 and older and have been sedentary for a long time, you should get checked before you start exercising or at least talk to your doctor,” Roberts says. Depending on a particular health profile and risk factors, a doctor may recommend treatments or tests to further investigate cardiac health.

It’s important to have cardiovascular disease risk factors treated -- taking medication for high cholesterol, for example. Some people at high risk for heart disease may also benefit from having a stress test, a test in which an individual’s heart is monitored while under exertion, such as jogging on a treadmill.

Stress tests are helpful in some people to clarify risk, but they’re not perfect. Roberts says he knows of one man whose stress test cleared him of any problems but who died while jogging three weeks later.

“If you have bad coronary arteries, it’s going to show up on a stress test,” he says. “If you have a small, unstable plaque that is ready to rupture, it won’t show up on a stress test.”

Health insurance companies will pay for stress tests and other cardiac tests if deemed medically necessary, such as in someone with heart disease or who appears to have heart disease. If a person has no evidence of heart disease but is still worried, paying out of pocket for a heart scan is another option. Such scans measure the amount of calcium in the arteries to give an indication of the amount of blockage.

Of course people with known heart disease should consult a doctor about exercise, says Dr. James C. Puffer, a sports medicine expert and president of the American Board of Family Medicine.

“Exercise is a benefit for people who want to prevent heart disease and for those who have it,” he says. “But the type of exercise that is most appropriate for people with heart disease is moderate [in intensity] and perhaps should even be monitored.”

But he notes, “Even after having a thorough medical evaluation and carefully developing an exercise program, while you can make it much safer, you can never take all of the risk out of it.”

That’s a good reason to pay attention to your body during exercise. Many studies suggest that people who die or have heart attacks during exercise had some warning signs of the impending event. These can include palpitations; chest pain, pressure or discomfort; dizziness or lightheadedness; blacking out; shortness of breath and nausea -- all symptoms that make you feel bad. Feeling sick or in pain shouldn’t occur during normal, healthy exertion, experts say.

Changes in exercise capacity can be a sign that the heart isn’t functioning as well, such as feeling more winded or more fatigued than you usually do for your level of activity

“The key,” says Roberts, “is listening to your body.”