Does one size fit all? The role of body mass index and waist circumference in systemic inflammation in midlife by race and gender

Objective: This study investigates the associations of body mass index (BMI) and waist circumference (WC) with markers of systemic inflammation in midlife by race and gender. Design: Data were obtained from the Survey of Midlife in the United States, a cross-sectional, observational study of Americans 35 years old or older (White men: N = 410; White women: N = 490; Black men: N = 58; Black women: N = 117). Inflammation was measured by concentrations of fibrinogen and C-reactive protein (CRP) in fasting plasma and concentrations of E-selectin and interleukin-6 (IL-6) in fasting serum. Anthropometric data were used to obtain BMI and WC. Socio-demographic and health-related factors were assessed with a survey. Multivariate models by race and gender were estimated to test the roles of BMI and WC for each inflammation marker. Results: Compared to White men, Black women have higher BMI and higher levels of all four inflammation markers; White women have lower BMI, lower WC, and lower E-selectin and fibrinogen but higher CRP; and Black men have higher fibrinogen. After adjusting for socio-demographic and health-related covariates as well as perceived discrimination, WC is associated with all four markers of inflammation among White men and women; with three markers (fibrinogen, CRP, and IL-6) of inflammation among Black women; and with CRP (and marginally with fibrinogen and E-selectin) among Black men. BMI is associated with higher CRP and fibrinogen among Black men (marginally so for White men) but not for women of either race. Conclusions: WC shows more consistent associations with inflammation markers than BMI, although the relationships vary by inflammation marker and population group. Our findings suggest that WC is a risk factor for systemic inflammation among White and Black men and women, and BMI is an additional risk factor for Black men.