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Physical Activity and Weight Affect Coronary Heart Disease Risk

Researchers have long known that both physical activity and excess weight affect the risk of coronary heart disease. However, it's been hard to tease apart how much each contributes. A new study found that being physically active can considerably, but not completely, lower the risk of cardiovascular disease associated with being overweight or obese.

The research stems from the Women's Health Study, begun in 1992 by NIH's National Cancer Institute (NCI) and National Heart, Lung and Blood Institute (NHLBI). Its original goals were to evaluate the effects of vitamin E and low-dose aspirin on cardiovascular disease and cancer in healthy women. Recognizing the value of the data they were collecting, the researchers extended the study to do more follow-up and evaluate other cardiovascular risk factors.

Dr. Amy Weinstein at the Beth Israel Deaconess Medical Center in Boston and colleagues at Brigham and Women's Hospital analyzed data collected in the Women's Health Study on almost 39,000 women who were 45 and older. They compared the participants' body mass index (BMI—a ratio of weight to height) and physical activity levels at the start of the study with cardiovascular outcomes (such as heart attacks) over an average of 11 years of follow-up.

In the April 28, 2008, issue of Archives of Internal Medicine, the researchers reported that the group had 948 cases of coronary heart disease during the follow-up period. The risk of coronary heart disease, they found, increased as BMI increased. Obese women were over twice as likely to have a coronary event as women in the normal weight category.

Overall, the women who were physically active were 31% less likely to have coronary heart disease than those who weren't active. After the researchers adjusted the data to account for other known influences—such as alcohol use, smoking and diet—the physically active women still had an 18% lower risk of coronary heart disease. In particular, the researchers found that physical activity significantly reduced the risk of coronary heart disease in the overweight and obese women.

The researchers also looked at the time the women spent walking and found that the more the women walked, the lower their risk for coronary heart disease. The greatest drop, for each weight category, was between those who didn't walk for exercise or recreation and those who walked 1-1.5 hours per week.

This study adds to a growing body of evidence showing that physical activity can help you live longer, regardless of whether you have excess weight. A half hour of moderate physical activity every day significantly reduces your risk of chronic disease, and more than 30 minutes further reduces the risk

Although walking and physical activity significantly reduced the risk of coronary heart disease among the overweight and obese women in this study, their risk didn't drop as low as normal-weight women. Both weight control and physical activity are important for preventing coronary heart disease.

—by Harrison Wein, Ph.D