The relationship between C-reactive protein and atherosclerosis differs on the basis of body mass index: the Dallas Heart Study.

OBJECTIVES: This study sought to evaluate whether the relationship between C-reactive protein (CRP) and atherosclerosis is modified by body mass index (BMI).
BACKGROUND: 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.
METHODS: 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.
RESULTS: 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.
CONCLUSIONS: 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.