Abstract 146: White Blood Cell Count and Risk of Stroke in Men and Women: the European Prospective Investigation into Cancer-Norfolk Prospective Population Study

Abstract

Background and Objectives: An elevated white blood cell (WBC) count has been reported to be associated with all-cause mortality and risk of cardiovascular diseases. While the relationship between leukocyte count and coronary heart disease has been well documented, evidence on the association with risk of stroke has been less consistent. The aim of this study was to investigate the relationship between WBC count and incidence of stroke in a large cohort of disease-free men and women, and to assess how far any associations might be explained by traditional risk factors for stroke. Methods: We examined the prospective association between full blood WBC count and incident stroke in 7,392 men and 9,049 women from the general population participating in the European Prospective Investigation into Cancer-Norfolk Study. Participants were aged 39-79 years, without known heart attack, stroke, and cancer at the baseline examination in 1993-1997 and were followed up for incident stroke till March 2008. Results: During the median follow-up of 12 years, 542 incident stroke cases were observed. The age- and sex- adjusted risk of incident stroke increased with the increase of WBC count. Compared to the lowest quartile of WBC count, the age- and sex- adjusted hazard ratios (HRs) and 95% CIs for stroke were 1.11 (0.86-1.45), 1.40 (1.10-1.79), and 1.65 (1.29-2.09) in the second, third, and fourth quartile, respectively. Adjusting for smoking attenuated the results, while further adjustment for socioeconomic and lifestyle risk factors changed the association very little. The association was further attenuated after adjustment for biological risk factors such as systolic blood pressure and a history of diabetes at baseline, but people with the highest quartile of WBC count still had a higher risk of stroke than those in the lowest quartile (HR 1.32, 95% CI 1.02-1.71). Every 2*10 9 /L increase in WBC count was associated with a hazard ratio of 1.14 (95% CI 1.02-1.26) for stroke in the fully-adjusted model which included age, sex, smoking status, BMI, social class, educational level, alcohol intake, physical activity, systolic blood pressure, a history of diabetes at baseline, and total serum cholesterol. Conclusions: A positive association between WBC count and stroke was observed in these middle-aged and older men and women. Adjustment for smoking attenuated the association while multivariate adjustment for other risk factors did not further change the results.