Lifetime physical activity and breast cancer risk in the Shanghai Breast Cancer Study

Overall physical activity in adolescence and adulthood, and changes in acti vity over the lifespan were analysed by in-person interviews among 1459 wom en newly diagnosed with breast cancer and 1556 age-matched controls in urba n Shanghai. Physical activity from exercise and sports, household, and tran sportation (walking and cycling) was assessed in adolescence (13-19 y) and adulthood (last 10 y), as was lifetime occupational activity Logistic regre ssion was used to estimate odds ratios (OR) and 95% confidence limits (OR ( 95% CL)) while controlling for confounders. Risk was reduced for exercise o nly in adolescence (OR = 0.84 (0.70-1.00)); exercise only in adulthood (OR = 0.68 (0.53-0.88)), and was further reduced for exercise in bath adolescen ce and adulthood (OR - 0.47 (0.36-0.62)). Graded reductions in risk were no ted with increasing years of exercise participation (OR1-5 yrs = 0.81 (0.67 -0.94); OR5-10 yrs = 0.74 (0.59-0.93); OR11-15 yrs = 0.55 (0.38-0.79); OR16 + yrs = 0.40 (0.27-0.60); P-trend < 0.01). Lifetime occupational activity also was inversely related to risk (P-trend < 0.01). These findings demonst rate that consistently high activity levels throughout life reduce breast c ancer risk. Furthermore, they suggest that women may reduce their risk by i ncreasing their activity levels in adulthood. (C) 2001 Cancer Research Camp aign.