Two of the magnesium-associated SNPs were significantly associated with atrial fibrillation, including the SNPs in the MUC1 (p = 0.02) and SHROOM3 (p = 2.4 × 10−4) genes, with the allele associated with higher serum magnesium concentrations being associated with lower risk of atrial fibrillation.32 The association between genetically predicted serum magnesium concentrations and cardioembolic stroke was attenuated after exclusion of those 2 SNPs, suggesting that the association may partly be mediated by atrial fibrillation. This evidence concerns the gene MUC1 and atrial fibrillation.