Inflammatory markers and long-term risk of ischemic heart disease in men: A 13-year follow-up of the Quebec Cardiovascular Study

We tested the hypothesis that elevated plasma interleukin-6 (IL-6), C-reactive protein (CRP) and fibrinogen concentrations are independent risk factors and interact in increasing the long-term risk of ischemic heart disease (IHD) in men. A total of 1982 IHD-free men from the Quebec Cardiovascular Study were followed over a period of 13 years during which 210 first fatal IHD events and non-fatal myocardial infarctions were recorded. Increased CRP levels (4th versus 1st quartile) were not associated with an increased risk of IHD after adjustment for non-lipid risk factors (age, body mass index, systolic blood pressure, diabetes, smoking and medication use at baseline), lipid risk factors (LDL and HDL cholesterol and triglyceride levels) and for IL-6 and fibrinogen (RR = 0.70, 95% CI = 0.43–1.13). High plasma IL-6 levels (4th versus 1st quartile) were associated with a 70% greater risk of IHD independent of confounding risk factors and of the other 2 inflammatory markers (RR = 1.71, 95% CI = 1.07–2.75). The relationship between high fibrinogen levels (4th versus 1st quartile) and IHD risk was borderline significant in multivariate analyses (RR = 1.53, 95% CI = 0.97–2.43). An inflammation score based on plasma IL-6 and fibrinogen levels improved the IHD risk predictive value of a multivariate model of traditional risk factors (p = 0.03). Including plasma CRP levels into the inflammatory score provided no additional predictive value. In conclusion, elevated plasma IL-6 concentrations are more strongly related to IHD risk than CRP and fibrinogen. An inflammation score based on high plasma IL-6 and fibrinogen levels used in combination with traditional risk factors may improve our ability to adequately identify high risk individuals.