Relative elevation in baseline leukocyte count predicts first cerebral infarction

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Abstract
Background: Atherosclerosis is an inflammatory disease, and leukocyte levels are associated with future risk of ischemic cardiac disease. Objective: To investigate the hypothesis that relative elevations in leukocyte count in a stroke-free population predict future ischemic stroke (IS). Methods: A population-based prospective cohort study was performed in a multiethnic urban population. Stroke-free community participants were identified by random-digit dialing. Leukocyte levels were measured at enrollment, and participants were followed annually for IS, myocardial infarction (MI), and cause-specific mortality. Cox proportional hazards regression models were used to calculate hazard ratios (HRs) and 95% CIs for IS, MI, and vascular death after adjustment for medical, behavioral, and socioeconomic factors. Results: Among 3,103 stroke-free community participants (mean age 69.2 ± 10.3 years) with baseline leukocyte levels measured, median follow-up was 5.2 years. After adjusting for stroke risk factors, each SD in leukocyte count (1.8 × 109 cells/L) was associated with an increased risk of IS (HR 1.22, 95% CI 1.05 to 1.42), and IS, MI, or vascular death (HR 1.13, 95% CI 1.02 to 1.26). Compared with those in the lowest quartile of leukocyte count, those in the highest had an increased risk of IS (adjusted HR 1.75, 95% CI 1.08 to 2.82). The effect on atherosclerotic and cardioembolic stroke was greater than in other stroke subtypes. Conclusion: Relative elevations in leukocyte count are independently associated with an increased risk of future ischemic stroke and other cardiovascular events.