June 20, 2006
Personal Health

By JANE E. BRODY

A previously healthy man in his late 40's died of a heart attack during the Turkey Trot on Long Island last year. Then on Memorial Day, another seemingly healthy man in his 50's went out for a run in Brooklyn and died.
When you hear about someone who has suffered a heart attack or sudden cardiac death while jogging, the immediate assumption is likely to be that jogging is dangerous to the heart. But is it?

The answer is somewhat paradoxical. While jogging, a person — especially someone with underlying heart disease — is more likely to die than if that person were walking or resting at that same moment. During vigorous exercise, the heart can develop an irregular beat, blood pressure can rise to a dangerous level or plaque from a partly clogged artery can break off and stop blood flow.

But — and this is a big but — over all, people who jog, including those with major cardiac risk factors, are less likely to have a heart attack in the long run than if they had not been joggers.

Reducing the Risk
Centuries ago it was commonly thought that the heart was limited to a certain number of beats and that those who used them up too fast would die young. We now know a lot better.

The heart is a muscle, and like any other muscle in the body, exercising it makes it stronger. It does not have to work as hard to get the job done. This is what is meant by "conditioning" the heart through moderately vigorous physical activity.

Conditioning occurs by exercising at a level that gets your heart rate within a target zone determined by your age (subtract your age from 220, then take 50 percent and 75 percent of that number to determine your zone).

A well-conditioned heart can pump in 50 beats the same amount of blood that the heart of a sedentary person would pump in 75 beats. In addition, during rest, a well-conditioned heartbeat is slower.

Among the major factors that increase a person's chance of developing coronary artery disease, the underlying cause of most heart attacks, are an elevated blood cholesterol level, high blood pressure, obesity, diabetes and undue stress.

The beauty of regular physical exercise is that it counters every one of these risk factors. Exercise also raises blood levels of HDL cholesterol, which helps to cleanse the arteries of deposits. The main risk factors exercise cannot change are family history and age. These two factors can serve as a warning.
If you have a family history of premature heart disease (heart attacks in first-degree relatives that occurred before 65), or if you are middle-aged or older and have been fairly sedentary for years, you would be wise to undergo a thorough physical exam before taking up jogging.

My father did not know this in 1967 when he tried jogging for the first time. His father and his father's brother had had heart attacks in their mid-50's. And although my father had always been physically active (brisk walking and swimming were his midlife activities), he had a heart attack about an hour after his first run.

Someone who should have known better, however, was James F. Fixx, who died of a heart attack while jogging on July 20, 1984. As the author of "The Complete Book of Running," Mr. Fixx was an international symbol of the jogging revolution. He also had a family history of heart disease; his father died of a heart attack at 43. And he himself had experienced cardiac symptoms in the weeks before his death, symptoms of one or more smaller heart attacks that he ignored.

The autopsy revealed that despite being physically active, Mr. Fixx had advanced coronary artery disease: one artery 99 percent clogged, a second 80 percent clogged and the third 70 percent clogged — in sum, a heart attack waiting to happen.
In the course of nearly every marathon, one or more runners keel over with a heart attack, and some die. Heat and dehydration are often contributing factors. In a 1987 study of heart attacks and sudden deaths in marathon runners, 81 percent of the victims had ignored warning symptoms.

The lesson here is to take reasonable precautions against sudden death:

• Make sure all cardiac risk factors — especially smoking — are absent or under control.
• If you have been sedentary for years or have any doubts about your cardiac well-being, get checked out beforehand. But keep in mind that passing an exercise stress test is not a guarantee of cardiac health.
• Establish a sensible training program, especially long before an event. All your muscles, not just your heart, need to be up to the stress.
• Run or walk at your own pace (the marathon is a race for only a few young, elite athletes).
• Stay well-hydrated with water at first, then with a sport drink if you sweat heavily or exercise for two or more hours.
• Pay attention to warning signs. If you experience upper body discomfort or pain that could be a symptom of coronary insufficiency during the activity, stop immediately and seek medical attention.

Symptoms that should not be ignored include palpitations; pain, pressure or discomfort in the chest; dizziness or lightheadedness; shortness of breath; and nausea.

In addition, if you find during your normal workout that you are getting more winded or fatigued for no apparent reason, that is a signal to get yourself examined.

Runners Do Live Longer
People with advanced heart disease are at risk of dying suddenly whether they exercise or not. But while vigorous exercise can precipitate a heart attack during a workout and for about an hour afterward, regular physical activity is an important preventive of sudden cardiac death.

For example, a study in Seattle of all people who died suddenly in one year showed that those with undetected heart disease were more likely to die during exercise, but they lowered their overall risk of sudden death if they exercised regularly. In other words, if those with heart disease avoided all exercise, their overall risk of sudden death would increase, not decrease.
And from a study of 7,620 joggers in Rhode Island, it was calculated that a middle-aged jogger with no known heart disease who ran for one more year was considerably less likely to die suddenly than was a middle-aged nonrunner who drove during that year.

In the long run, various studies have found, jogging adds years to life. Over all, each hour spent exercising (up to 30 hours a week) adds about two hours to a person's life expectancy, according to the Harvard Alumni Study, which has tracked deaths among 17,000 men for more than two decades.
Even those who did not start exercising until midlife had a 23 percent lower risk of death over the next 20-odd years. Endurance activities like running, cycling, lap swimming, brisk walking and cross-country skiing conferred the greatest benefit, adding six years of life expectancy over that of a couch potato.