Body fat distribution and obesity in pre- and postmenopausal breast cancer

Background Excessive body weight is known to increase the risk of postmenop ausal, but not premenopausal breast cancer. Some studies have suggested tha t being overweight is protective against premenopausal breast cancer, but t he evidence is not compelling. Much less is known about the role of body fa t distribution in either pre- or postmenopausal breast cancer. Methods Breast cancer risk was examined in relation to body weight, height, Quetelet index (kg/m(2)), and waist/hip ratio (WHR) in the New York Univer sity Women's Health Study, a prospective cohort study. Cases were 109 preme nopausal and 150 postmenopausal women diagnosed with breast cancer between 1985 and 1994. Non-cases were 8157 cohort members free of breast cancer. Results Among premenopausal women, there was an increasing risk of breast c ancer with increasing WHR. The relative risk (RR) of breast cancer increase d to 1.72 (95% confidence interval [CI]:1.0-3.1) in the upper quartile of W HR. The association was limited to subjects who had elevated Quetelet index , but not among those with lower weight. Overall, Quetelet index itself was not related to breast cancer risk in the premenopausal group, but there wa s a protective association among those ranking below the median WHR. Ln pos tmenopausal women, the RR for breast cancer increased to 2.36 (95% CI : 1.4 -3.9) in the upper quartile of Quetelet index, but there was no association with WHR. Height was not associated with breast cancer in this study. Conclusions The study confirms that excessive body weight increases breast cancer risk in postmenopausal women. On the contrary, in premenopausal wome n, excessive body weight may be protective among women who have a lower-bod y type of fat accumulation (low WHR). An upper-body fat accumulation (high WHR) is a predictor of breast cancer risk in premenopausal women, and this effect is especially pronounced among subjects who are overweight.