RESEARCH ARTICLE Association of White Blood Cell Count and Differential with the Incidence of Atrial Fibrillation: The Atherosclerosis Risk in Communities (ARIC) Study

Background Although inflammation is involved in the development of atrial fibrillation (AF), the associa-tion of white blood cell (WBC) count and differential with AF has not been thoroughly exam-ined in large cohorts with extended follow-up. Methods We studied 14,500 men and women (25 % blacks, 55 % women, mean age 54) free of AF at baseline (1987–89) from the Atherosclerosis Risk in Communities (ARIC) study, a commu-nity-based cohort in the United States. Incident AF cases through 2010 were identified from study electrocardiograms, hospital discharge records and death certificates. Multivariable Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95 % con-fidence intervals (CI) for AF associated with WBC count and differential. Results Over a median follow-up time of 21.5 years for the entire cohort, 1928 participants had inci-dent AF. Higher total WBC count was associated with higher AF risk independent of AF ris