Reduced atrial fibrillation risk via decreased expression of HCN3 and SCN3A (via HCN channel blockers and sodium channel blockers, respectively) were associated with reduced T2D risk in the MR analysis; however, only sodium channel blockers were observed to reduce T2D risk (T2D OR = 0.25, 95% CI = 0.17, 0.39, p = 4.7 x 10−11 [IVW MR association]). This evidence concerns the gene SCN3A and atrial fibrillation.