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By CHRISTOPHER VAUGHAN Your ability to push yourself hard when exercising is a better predictor of longevity than any other common measure, said researchers at Stanford University Medical Center and the Veterans Affairs Palo Alto Health Care System. Their study, published in the March 14 issue of The New England Journal of Medicine, measured peak exercise capacity of 6,200 men and compared that measure to the subjects' mortality over 10 years. Peak exercise capacity, a measure of how hard people can exercise before they can no longer continue, is considered a good indicator of cardiovascular fitness. Many studies have shown that improving fitness can lower your risk of cardiovascular disease, and still others have shown that if you have heart disease, exercise capacity is a good indicator of mortality. But this is the first study to corrolate exercise capacity and mortality in people who don't have cardiovascular disease as well as those who do. "What we found was that exercise capacity is similarly important in [both groups]," said Jonathan Myers, PhD, lead author.
In the study, the men were put on a treadmill that increased in speed and angle until they could no longer run or started to feel chest pains. Their maximum effort was measured in "metabolic equivalents" or MET. One MET is the amount of oxygen the average person uses while sitting down, while five MET is about what one consumes while walking at 4 mph, and 8 MET is what most people consume while jogging at 6 mph. John Atwood, MD, professor of medicine at the VA, and his colleagues found that for every MET increase in a man's exercise capacity, the risk of mortality dropped by 12 percent. Those with a maximum capacity of less than 5 MET had double the chance of dying (from any cause) of those with an exercise capacity of 8 MET or more. "Our results show that exercise capacity is a strong predictor of the risk of death," Myers said. Furthermore, exercise capacity was a better predictor of mortality risk than many other commonly used measurements, Myers and his colleagues said. How hard you can exercise is a better measure than how much you smoke, or whether you have hypertension or diabetes, for instance. Exercise capacity also did better predicting survival than other measurements, such as peak heart rate. The authors did point out qualifiers to their study. Because it included only men, they don't know if results apply equally to women. Furthermore, while they have shown a relationship between exercise capacity and mortality, they cannot reveal if the relationship is causal -- that is, whether improving exercise capacity directly decreases chances of dying. Still, the study's authors said, the evidence that we have is enough for physicians and patients to act upon. "In terms of reducing mortality from any cause, improving exercise tolerance warrants at least as much attention as the other major risk factors for patients who have cardiovascular disease or are at high risk for it," Myers said.
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Stanford Report, March 20, 2002
