In the present study, we demonstrated that elevated plasma levels of Th17- related cytokines, including IL-17A, IL-17F, IL-21, IL-22 and IL-6, along with IFN-γ, IL-10 and IL-9, were independently associated with increased risk of AF, suggesting that Th17 cells may be involved in the pathogenesis of AF. This evidence concerns the gene IL9 and atrial fibrillation.