The Relationship Between C-Reactive Protein and Atherosclerosis Differs on the Basis of Body Mass Index: The Dallas Heart Study

Abstract

This study sought to evaluate whether the relationship between C-reactive protein (CRP) and atherosclerosis is modified by body mass index (BMI). CRP levels are affected by obesity, and it is unknown whether the associations between CRP and cardiovascular (CV) disease differ between obese and nonobese individuals. We measured CRP and multiple atherosclerosis phenotypes, including coronary artery calcification (CAC) (n = 2,685), aortic wall thickness (AWT) (n = 2,238), and aortic plaque burden (APB) (n = 2,224), in subjects ages 30 to 65 years from the Dallas Heart Study. The associations of CRP with CAC, AWT, and APB were compared across categories of BMI (normal, 18.5 to <25 kg/m(2); overweight, 25 to <30 kg/m(2); obese, ≥30 kg/m(2)) in sex-stratified analyses. The overall prevalence of obesity was 38% in men and 53% in women. Increasing CRP levels (<1 mg/l, 1 to 3 mg/l, >3 mg/l) were associated with increased CAC prevalence in normal and overweight men and in normal weight women (p < 0.01), but not in obese subjects of either sex. Likewise, the correlations between CRP and AWT and APB diminished with increasing BMI and were nonsignificant in obese individuals (p < 0.05 in nonobese, p > 0.1 in obese). Interaction tests between CRP and obesity were significant for all atherosclerosis measures in men and for AWT and ABP in women (p interaction <0.05 each). In both sexes, the c-statistics of CRP for all 3 atherosclerosis measures were greater for normal weight than obese individuals. In a large, population-based study, the association between CRP and multiple measures of atherosclerosis is diminished in obese individuals. The role of CRP for predicting CV outcomes in obese subjects requires further evaluation.