Baseline recreational physical activity, history of sports participation, and postmenopausal breast carcinoma risk in the Netherlands Cohort Study

BACKGROUND. The aim of the current study was to evaluate the relation betwe en physical activity and breast carcinoma risk with specific emphasis on in teraction with other aspects of energy balance. METHODS. The Netherlands Cohort Study on diet and cancer was conducted amon g 62,537 women ages 55-69 years at baseline. Information regarding baseline recreational physical activity, history of sports participation, and occup ational physical activity was collected with a questionnaire in 1986. After 7.3 years of follow-up, 1208 incident breast carcinoma cases were availabl e for case-cohort analyses. RESULTS. A summed total of baseline recreational physical activity (includi ng walking, cycling, gardening) showed an inverse association with breast c arcinoma risk. Women who were active in the above-mentioned activities for > 90 minutes a day had a rate ratio (RR) of 0.76 (95% confidence interval [ 95% CI], 0.58-0.99) compared with women who were active < 30 minutes a day. Women who ever participated into sports before baseline had a RR of 1.13 ( 95% Cl, 0.94-1.37) compared with women who never participated in sports. Th e relation between sports participation and breast carcinoma risk did not a ppear to be dependent on the time window of participation (before/after men arche, before/after birth of the first child, before/after age 20 years). N o interaction was found between baseline recreational physical activity, bo dy mass index (BMI) (kg/m(2)), energy intake, and weight gain/loss during a dult life in relation to breast carcinoma, although in the subgroup of wome n with a high BMI we found a stronger inverse relation between recreational physical activity and breast carcinoma risk independent of energy intake. Occupational physical activity was not found to be related to breast carcin oma risk. CONCLUSIONS. The current study findings support the hypothesis that recreat ional physical activity is associated inversely with breast carcinoma risk. (C) 2001 American Cancer Society.