Relative elevation in baseline leukocyte count predicts first cerebral infarction.

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 x 10(9) 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.