Background: Racial differences exist in overall (BMI) and central adiposity (abdominal visceral fat (VAT)) measures. Recently, it has been shown that white men have higher volumes of cardiovascular fat (CF) that were found to be greater per increment increase in BMI when compared to black men. It is unknown whether similar racial differences exist in women. We assessed whether CF volumes vary by race and tested the effect modification of race on the associations between adiposity measures and CF among women at midlife, a time period marked with increased cardiovascular risk.
Methods: Volumes of CF depots (epicardial fat (EAT), paracardial fat (PAT), total heart fat (TAT), and aortic perivascular fat (PVAT)), BMI, and VAT were examined among participants from the Study of Women’s Health Across the Nation (SWAN) Cardiovascular Fat Ancillary study. Linear regression was used for statistical analyses. All adiposity measures were log-transformed to achieve normality.
Results: A total of 543 women (mean age: 50.9 ± 2.9 years; 34% postmenopausal) were included. Women were either white (62%) or black (38%). Significant racial differences existed in volumes of all CF depots with white women having higher volumes compared to black women, after adjusting for age, menopausal status, hypertension, diabetes, and alcohol consumption (all P-values <0.05). These racial differences remained significant after further adjustment for BMI or VAT, with one exception of PAT after adjusting for VAT. Race significantly modified the associations between VAT and EAT (Interaction P-value=0.03) and between BMI and PAT (Interaction P-value=0.01), such that black women had more EAT than white women for every one-increment increase in VAT, while with every one-increment increase in BMI, white women had more PAT than black women. Race-stratified analyses confirmed the effect modification of race on the associations between VAT and EAT (effect size per 1 unit increase in VAT was higher in blacks (β (SE) = 0.62 (0.05) than in whites (β (SE) 0.51 (0.04)) and between BMI and PAT (effect size per 1 unit increase in BMI was higher in whites (β (SE) = 2.56 (0.18) than in blacks (β (SE) 1.92 (0.23)).
Conclusions: Racial differences existed in CF volumes in midlife women similar to midlife men. Black women with greater central adiposity had higher EAT volumes than white women, while white women with greater overall adiposity had higher PAT volumes than black women. Future research should evaluate the impacts of these significant racial differences in explaining CVD risk disparity.