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To evaluate whether recreational physical activity is associated with breast cancer among young women, the authors analyzed data from a population-based case-control study. Cases (n = 1,668) were women under age 45 years who had been newly diagnosed with breast cancer between 1990 and 1992 in Atlanta, Georgia, central New Jersey, or Seattle, Washington. Controls (n = 1,505) were frequency-matched to cases by 5-year age group and geographic area of residence. Breast cancer was not associated with recreational activity in any of the three time periods assessed (highest quartile of activity vs. lowest: age- and center-adjusted odds ratio (OR) = 0.94 (95% confidence interval (CI) 0.77-1.15) at ages 12-13 years, OR = 1.08 (95% CI 0.88-1.32) at age 20 years, and OR = 1.18 (95% CI 0.97-1.44) during the past year), with the average of the three time periods (OR = 1.02, 95% CI 0.84-1.25), or with daily climbing of at least two flights of stairs (without stopping) during the past year (daily climbing vs. never climbing: OR = 1.03, 95% CI 0.86-1.23). Estimates were not modified or confounded by body mass index, menopausal status, or caloric intake during the past year. These results do not support a protective role for physical activity in the risk of breast cancer among young women.
Gammon et al. (Sun,) studied this question.