Univariate analysis showed a negative correlation between AF and circulating irisin (r =0.227, P<0.001), BMI (r = –0.21, P=0.033), systolic blood pressure (SBP) (r = –0.19, P=0.047), TC (r =0.217, P<0.001), LDL-C (r =0.23, P=0.004), TG (r =0.123,P=0.023), CRP (r = –0.31, P<0.001), HbA1c (r =0.251, P<0.001), log-HOMA-IR (r =0.256, P=0.021) and log-Fins (r = –0.260, P<0.001). Here, FNDC5 is linked to atrial fibrillation.