Body size and breast cancer risk assessed in women participating in the Breast Cancer Detection Demonstration Project.

In a case-control study that included 2,560 breast cancer cases and 2,679 controls, the authors examined the association between body size and breast cancer with the use of measured height and weight of white US women. The subjects were women aged 26-93 years recruited between 1973 and 1975 for participation in the Breast Cancer Detection Demonstration Project, a nationwide breast cancer screening program. After controlling for the effect of potential confounders, the relative risks of breast cancer across increasing quartiles of height were 1.00, 1.07, 1.15, and 1.27 (p = 0.001, test for trend). The effect of weight independent of height was evaluated using indices of relative weight (e.g., weight/height1.5, weight/height2), and the authors identified excess weight as a risk factor for breast cancer among women who had experienced natural menopause and among women aged 50 years or older at diagnosis. Among women aged 50 years or older, for example, the relative risks of breast cancer for increasing quartiles of weight/height1.5 were 1.00, 1.04, 1.40, and 1.29 (p = 0.0006, test for trend). An inverse association between relative weight and breast cancer risk was suggested for women younger than age 50 years at diagnosis. However, the apparent protective effect of high relative weight was restricted to women with small tumors, suggesting a detection bias.