High-Sensitivity C-Reactive Protein and Interleukin-6–Dominant Inflammation and Ischemic Stroke Risk

Background and Purpose— Interleukin-6 (IL-6) is a proinflammatory cytokine with known autoregulatory feedback mechanisms. We hypothesized that elevated high-sensitivity C-reactive protein (hsCRP) relative to IL-6 confers an increased risk of ischemic stroke (IS), and low hsCRP relative to IL-6 a decreased risk, for individuals in the prospective, multiethnic, population-based Northern Manhattan Study (NOMAS). Methods— Serum hsCRP and IL-6 were measured in NOMAS participants at baseline. We created a trichotomized predictor based on the dominant biomarker in terms of quartiles: hsCRP-dominant, IL-6–dominant, and codominant groups. Cox proportional hazards models were used to calculate hazard ratios and 95% confidence intervals for the association between inflammatory biomarker group status and risk of incident IS. Results— Of 3298 participants, both hsCRP and IL-6 were available in 1656 participants (mean follow-up, 7.8 years; 113 incident IS). The hsCRP-dominant group had increased risk of IS (adjusted hazard ratio, 2.62; 95% confidence interval, 1.56–4.41) and the IL-6–dominant group had decreased risk (adjusted hazard ratio, 0.38; 95% confidence interval, 0.18–0.82) when compared with the referent group, after adjusting for potential confounders. Model fit was improved using the inflammation-dominant construct, over either biomarker alone. Conclusions— In this multiethnic cohort, when hsCRP-quartile was higher than IL-6 quartile, IS risk was increased, and conversely when IL-6 quartiles were elevated relative to hsCRP, IS risk was decreased. Construct validity requires confirmation in other cohorts.