The Relationship Between C-Reactive Protein and Atherosclerosis Differs on the Basis of Body Mass Index: The Dallas Heart Study
Is the relationship between C-reactive protein (CRP) and atherosclerosis modified by body mass index (BMI)?
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 30-65 years from the Dallas Heart Study, were measured. The associations of CRP with measures of atherosclerosis were compared across categories of BMI (normal, 18.5 to <25 kg/m2; overweight, 25 to <30 kg/m2; obese, ≥30 kg/m2) in sex-stratified analyses.
Obesity was present in 38% of men and 53% of women. Increasing CRP levels (<1 mg/L, 1-3 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. 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 three atherosclerosis measures were greater for normal-weight than obese individuals.
The authors concluded that the association between CRP and multiple measures of atherosclerosis is diminished in obese individuals.
CRP is a nonspecific marker that is elevated in a variety of inflammatory states. When inflammatory states other than atherosclerosis are present, they obscure the association between atherosclerosis and CRP. Since obesity is an inflammatory condition, it is not surprising that CRP may be less useful in the setting of obesity, even though CRP may partially reflect the vascular risk associated with obesity. More specific markers, or a panel of biomarkers, may be better suited to monitor atherosclerotic burden. Studies with actual cardiovascular events are also needed to assess usefulness of these markers in predicting vascular risk.
Keywords: C-Reactive Protein, Atherosclerosis, Body Mass Index, Biological Markers, Overweight
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