Long-term Recreational Physical Activity and Breast Cancer in the National Health and Nutrition Examination Survey I Epidemiologic Follow-up Study

Abstract

Our purpose was to study the association between long-term recreational physical activity and breast cancer in the Epidemiological Follow-up Study (NHEFS) of the first National Health and Nutrition Examination Survey (NHANES I, 1971–1975). The analytic cohort included 6160 women who were free of breast cancer at the first NHEFS follow-up in 1982–1984 and had interview data on recreational physical activity (low, moderate, and high) in 1982–1984 and 10 years earlier, in 1971–1975. We created categories of long-term (1982–1984 + 1971–1975) recreational physical activity: (a) consistently low; (b) moderate/inconsistent; and (c) consistently high. Data were analyzed using Cox proportional hazard regression models. A total of 138 women developed breast cancer between 1982–1984 and 1992. In women ≥50 years of age in 1982–1984, consistently high (versus consistently low) recreational physical activity was associated with a 67% reduction in breast cancer risk (n = 96 cases; relative risk, 0.33; 95% confidence interval, 0.14–0.82; P for trend = 0.03); in women <50 years of age (n = 42 cases), there was no association. Associations were not modified by body mass index or by weight gain as an adult. High recreational physical activity over the long-term may reduce breast cancer risk in women ≥50 years of age; in this sample, it did so regardless of weight history.