American Journal of Epidemiology Original Contribution Case-control Study of Body Size and Breast Cancer Risk in Nigerian Women

Previous studies have shown that weight is inversely associated with premenopausal breast cancer and positively associated with postmenopausal disease. Height has been shown to be positively correlated with breast cancer risk, but the association was not conclusive for premenopausal women. These previous studies were conducted primarily in Western countries, where height is not limited by nutritional status during childhood. The authors assessed the association between breast cancer and anthropometric measures in the Nigerian Breast Cancer Study (Ibadan, Nigeria). Between 1998 and 2009, 1,233 invasive breast cancer cases and 1,101 controls were recruited. The multivariate-adjusted odds ratio for the highest quartile group of height relative to the lowest was 2.03 (95% confidence interval for each 5-cm increase, with no difference by menopausal status. Comparing women with a body mass index in the lowest quartile group, the adjusted odds ratio for women in the highest quartile category was 0.72 (95% CI: 0.54, 0.94; P-trend ¼ 0.009) for premenopausal and post-menopausal women. Influence of height on breast cancer risk was quite strong in this cohort of indigenous Africans, which suggests that energy intake during childhood may be important in breast cancer development. Breast cancer ranks second in global cancer incidence and is the most common cancer diagnosis among Nigerian women (1–4). While breast cancer incidence has been shown to have stabilized or to be decreasing in some Western countries, the breast cancer burden has steadily increased in many developing countries with traditionally low incidence rates (5, 6). Among factors proposed to contribute to the rising incidence in these societies are secular changes in lifestyle and reproductive factors. The influence of anthropometric measures on breast cancer risk has been the subject of many studies (7–13). The relation between body weight and breast cancer risk is modified by menopausal status, with higher weight or body mass index (BMI) associated with increased risk for post-menopausal women and reduced risk for premenopausal women. Height is linked to increased breast cancer risk for postmenopausal women, and the association is less clear for premenopausal women. However, these findings were derived from studies conducted mainly in Western countries, where the prevalence of obesity is relatively high and attained height is not limited by nutritional status in childhood. Therefore, the influence of body size on breast cancer risk in developing countries remains unclear. Nigerian women have a low prevalence of obesity (14), and childhood growth in developing countries can be limited …