Age and duration of follow-up as modulators of the risk for ischemic heart disease associated with high plasma C-reactive protein levels in men

Background: Plasma C-reactive protein (CRP) levels recently have been identified as an emerging risk factor for ischemic heart disease (IHD). However, whether plasma CRP levels predict an increased risk for future IHD beyond traditional risk factors has yet to be evaluated in a large prospective, population-based study. Methods: The association between elevated plasma CRP levels and the risk for future IHD was investigated in the prospective, population-based cohort of 2037 IHD-free middle-aged men from the Quebec Cardiovascular Study. During a 5-year follow-up, 105 first IHD events were recorded. Baseline plasma CRP levels were measured using a highly sensitive assay. Results: High plasma CRP concentrations (equal to or above vs below the median level of 1.77 mg/L) were associated with a significant 1.8-fold increase in IHD risk (95% confidence interval [CI], 1.2-2.7). This association remained significant after adjustment for lipid risk factors but not when the simultaneous contribution of nonlipid traditional risk factors was taken into account. Multivariate analyses indicated that CRP level predicted short-term risk for IHD (events that occurred less than or equal to2 years after the baseline evaluation), but not long-term risk (>2 years). Moreover, high plasma CRP levels predicted an increased risk for IHD, independent of any other confounder, in younger (less than or equal to 55 years) but not in older (>55 years) individuals. Conclusion: Plasma CRP levels may provide independent information on IHD risk only in younger middle-aged men and in the case of IHD events that may occur relatively soon after the baseline evaluation.