Background: Interleukin (IL)-18 promotes atherosclerotic plaque growth and vulnerability. It is unknown, however, whether elevations of circulating IL-18 precede the onset of coronary events in apparently healthy individuals.
Methods and results: We evaluated the relationship between baseline plasma levels of IL-18 and the subsequent incidence of coronary events over a 5-year follow-up in the Prospective Epidemiological Study of Myocardial Infarction (PRIME),which included 10 600 healthy European men aged 50 to 59 years at baseline. Analysis was performed in a nested case-control manner comparing 335 cases with a coronary event to 670 age-matched controls. Baseline levels of IL-18 were significantly higher in men who developed a coronary event than in controls (225.1 versus 203.9 pg/mL, P=0.005). After adjustment for most potential confounders, including C-reactive protein, IL-6, and fibrinogen, the relative risk of future coronary events associated with increasing tertiles of IL-18 was 1.65 (95% CI 1.14 to 2.40, P=0.008) in Northern Ireland, 1.29 (95% CI 0.96 to 1.73, P=0.09) in France, and 1.42 (95% CI 1.13 to 1.79, P=0.003) in both populations combined (P=0.31 for the test of homogeneity between populations). In all models, IL-18 made an independent contribution to the prediction of risk over lipids or other inflammatory markers such as C-reactive protein, IL-6, or fibrinogen.
Conclusions: Plasma IL-18 level was identified as an independent predictor of coronary events in healthy, middle-aged European men. Determination of circulating IL-18 might improve the prediction of coronary events.