Occupational physical activity and the risk of breast cancer

The association between occupational and the risk of breast cancer was analyzed using data from a case-control study of 257 women with breast cancer and 565 control women. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for occupations having light and medium activity compared with sedentary ones. After adjusted for potential confounders, women in sedentary occupations had a 29% higher risk, compared to those with the physically medium demanding jobs. For women at age > or =55 years higher occupational physical levels were associated with 53-60% reduction in the risk. There was a significant decreasing trend in the ORs from sedentary to medium work (P=0.001); while no association emerged in younger women. These findings demonstrate that the protective effect of higher levels activity in occupations on breast cancer appears to be confined to older women.