Background: Elevated serum C-reactive protein (CRP) is a predictor of coronary heart disease in population samples. We studied the contribution of the simultaneous presence (joint effects) of elevated CRP and the classic as well as some new risk factors on acute coronary events.
Methods: With a nested case-control design and logistic regression analyses, we measured baseline and pre-event CRP levels in patients who had myocardial infarction or coronary death (cases) during an 8.5-year follow-up in the Helsinki Heart Study, a coronary primary prevention trial in dyslipidemic middle-aged men. The control patients were participants remaining free of coronary events.
Results: Baseline and pre-event CRP levels were higher in cases than in control patients (4.4 vs 2.0 mg/L, P <.001 and 6.0 vs 3.6 mg/L, P <.001). The relative risk attributed to elevated CRP was 40% higher with chronic elevation (odds ratio [OR], 3.34) compared with high baseline (OR, 2.24) or pre-event (OR, 2.26) level only. Hypertension, low high-density lipoprotein cholesterol, and high leukocyte count increased the risk only marginally without simultaneous occurrence of high CRP, whereas the joint effects of CRP and these classic risk factors suggested additive effects on coronary risk. In contrast, high levels of immunoglobulin G-class antibodies to oxidized low-density lipoprotein and antiprothrombin antibodies as well as high total immunoglobulin G level increased the risk irrespective of CRP.
Conclusions: Elevated CRP enhances the risks attributed to classic coronary risk factors.