The aim of the current study was to evaluate the relation between physical activity and breast carcinoma risk with specific emphasis on interaction with other aspects of energy balance.
The Netherlands Cohort Study on diet and cancer was conducted among 62,537 women ages 55-69 years at baseline. Information regarding baseline recreational physical activity, history of sports participation, and occupational physical activity was collected with a questionnaire in 1986. After 7.3 years of follow-up, 1208 incident breast carcinoma cases were available for case-cohort analyses.
A summed total of baseline recreational physical activity (including walking, cycling, gardening) showed an inverse association with breast carcinoma 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% CI, 0.94-1.37) compared with women who never participated in sports. The relation between sports participation and breast carcinoma risk did not appear to be dependent on the time window of participation (before/after menarche, before/after birth of the first child, before/after age 20 years). No interaction was found between baseline recreational physical activity, body mass index (BMI) (kg/m(2)), energy intake, and weight gain/loss during adult life in relation to breast carcinoma, although in the subgroup of women 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 carcinoma risk.
The current study findings support the hypothesis that recreational physical activity is associated inversely with breast carcinoma risk.