The body mass index-mortality relationship in white and African American women

Objective: To examine the association of body mass index to all-cause and cardiovascular disease (CVD) mortality in white and African American women. Research methods and procedures: Women who were members of the American Cancer Society Prevention Study I were examined in 1959 to 1960 and then followed 12 years for vital status. Data for this analysis were from 8,142 black and 100,000 white women. Body mass index (BMI) was calculated from reported height and weight. Associations were examined using Cox proportional hazards modeling with some analyses stratified by smoking (current or never) and educational status (less than complete high school or high school graduate). Results: There was a significant interaction between ethnicity and BMI for both all-cause (p<0.05) and CVD mortality (p<0.001). BMI (as a continuous variable) was associated with all-cause mortality in white women in all four groups defined by smoking and education. In black women with less than a high school education, there were no significant associations between BMI mortality. For high school-educated black women, there was a significant association between BMI and all-cause mortality. Among never smoking women with at least a high school education, models using the lowest BMI as the reference indicated a 40% higher risk of all-cause mortality at a BMI of 35.9 in black women vs. 27.3 in white women. Discussion: The impact of BMI on mortality was modified by educational level in black women; however, BMI was a less potent risk factor in black women than in white women in the same category of educational status.