Clinical and experimental data support a critical role for inflammation in cardiovascular disease. The purpose of the current study was to examine the relation between an inflammatory marker, neutrophil-to-lymphocyte ratio (NLR), and incident atrial fibrillation (AF) in asymptomatic adults. We investigated 21,118 self-referred men and women who were annually screened in a tertiary medical center. All subjects were free of AF at baseline and had their serum NLR calculated at the first annual visit. Subjects were divided into 2 groups based on their baseline NLR: Low (