Adult BMI change and risk of Breast Cancer: National Health and Nutrition Examination Survey (NHANES) 2005-2010

Objective Breast cancer is the second leading cause of cancer mortality among women in the developed world. This study assessed the association between occurrence of breast cancer and body mass index (BMI) change from age 25 to age closest to breast cancer diagnosis while exploring the modifying effects of demographic variables. Methods The National Health and Nutrition Examination Survey data were used. Women included were >= 50 years, not pregnant and without a diagnosis of any cancer but breast. The total sample included 2895 women (172 with breast cancer and 2723 controls with no breast cancer diagnosis). Multivariate logistic regression was used to estimate the OR and 95 % CIs and interaction evaluated by including an interaction term in the model. Results Women whose BMI increased from normal or overweight to obese compared to those who remained at a normal BMI were found to have a 2 times higher odds (OR = 2.1; 95 % CI 1.11-3.79) of developing breast cancer. No significant association was observed for women who increased to overweight. However, a more pronounced association was observed in non-Hispanic black women (OR = 6.6; 95 % CI 1.68-25.86) and a significant association observed when they increased from normal to overweight (OR = 4.2; 95 % CI 1.02-17.75). Conclusions Becoming obese after age 25 is associated with increased risk of breast cancer in women over 50 years old, with non-Hispanic black women being at greatest risk.