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Letters
January 22/29, 2003

Exercise Intensity and Risk of Coronary Heart Disease

Author Affiliations
 

Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.

JAMA. 2003;289(4):419-420. doi:10.1001/jama.289.4.419-a

In Reply: In response to Dr Burack, we performed our analysis again, controlling for aspirin use. The results were virtually unchanged; the multivariate relative risks (95% confidence intervals) for CHD across quintiles of total physical activity additionally controlled for aspirin were 1.00, 0.91 (0.79-1.05), 0.87 (0.75-1.00), 0.84 (0.72-0.98), and 0.71 (0.61-0.84).

Dr Brody points out that some forms of exercise were not significantly related to heart disease risk. The main findings of our study were that total volume of activity and the intensity of activity were significant predictors of CHD. We had less statistical power to look at each individual activity, especially those not commonly performed. This was reflected in the wide confidence intervals for these analyses. We also noted that some participants may have spent less than reported time in actual play (eg, for racquet sports) or performed at lower than standard intensity (eg, 7 metabolic equivalents for swimming or biking). Such random misclassification of exposure tends to bias results toward the null.

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