Is body mass index (BMI) related to breast cancer risk?
More recent studies have focused on BMI as it is considered a better measure of obesity than body weight. The relationship between BMI and breast cancer risk is similar to that seen for body weight. In the same combined analysis of seven cohort studies described above, postmenopausal women with a BMI greater than 33 had an weak increase in the risk of breast cancer (relative risk =1.27) compared to women with a BMI less than 21. A BMI greater than 33 was associated with a moderate decrease in breast cancer risk (relative risk = 0.58) among premenopausal women with a BMI greater than 33 compared to lighter women. Some epidemiologic studies have failed to find a relationship between BMI and breast cancer risk among postmenopausal women who used hormone therapy. This effect is due to a masking of the effect of obesity by hormone therapy which also increases breast cancer risk. (see Are there factors that may modify the relationship between obesity and breast cancer risk? below). These stu
