Elevated white blood cell count and carotid plaque thickness - The Northern Manhattan Stroke Study

Background and Purpose-Elevated leukocyte count has been associated with ca rdiovascular and cerebrovascular disease in several epidemiological studies . We sought to determine whether white blood cell count (WBC) is associated with carotid plaque thickness in a stroke-free, multiethnic cohort. Methods-For this cross-sectional analysis,WBC was measured in stroke-free c ommunity subjects undergoing carotid duplex Doppler ultrasound. Maximal int ernal carotid plaque thickness (MICPT) was measured for each subject. Demog raphic and potential medical confounding factors were analyzed with linear and logistic regression to calculate the effect of quartile of WBC on MICPT . Odds ratios (ORs) and 95% confidence intervals (CIs) for the effect of qu artile of WBC on MICPT greater than or equal to 75th percentile were calcul ated. All analyses were stratified by race-ethnicity. Results-The mean age of the 1422 subjects was 68.6 +/- 10.2 years; 40.0% we re men; 24.4% were white, 46.9% Hispanic, and 26.7% black. Among Hispanics, compared with the lowest quartile of WBC, those in the highest quartile ha d significantly increased MICPT (mean difference = 0.30 mm, P=0.0086) after adjustment for age, sex, and other atherosclerotic risk factors. There was no significant increase for blacks or whites. The OR for MICPT greater tha n or equal to 75th percentile (1.9 mm) was significantly increased for Hisp anics (OR, 2.8; 95% CI, 1.4 to 5.6), marginally elevated for black non-Hisp anics (OR, 1.6; 95% CI, 0.8 to 3.2), and not increased for white non-Hispan ics (OR, 0.5; 95% CI, 0.2 to 1.1). Conclusions-Relative elevation in WBC is associated with carotid atheroscle rosis, but this relationship differs by race-ethnicity. The association is strongest in Hispanics, intermediate in black non-Hispanics, and not presen t in white non-Hispanics in this population. Chronic subclinical infection or inflammation may account for this association.