Assessing the causal associations of atrial fibrillation with serum uric acid level and gout: insights from a bidirectional mendelian randomization study

Numerous observational studies consistently highlight a strong association between serum uric acid (sUA) levels and atrial fibrillation (AF). However, the causal relationship and the direction of this association remain elusive, despite extensive research efforts. This study aimed to investigate the bidirectional causal relationships between sUA, gout, and the risk of AF using the two-sample Mendelian randomization (MR) approach. We conducted a comprehensive analysis utilizing publicly available genome-wide association studies (GWAS) summary statistics, employing stringent criteria to meticulously select genetic variants associated with sUA, gout, and AF. Our primary analytical approach was the inverse-variance weighted (IVW) method, complemented by some sensitivity analyses, including MR-Egger, weighted median, simple mode, and weighted mode, to estimate the causal effects. To identify potential violations, we conducted Egger regression and leave-one-SNP-out analyses. We assessed the strength of instrumental variables using F values to evaluate weak instruments. Additionally, we referenced the Phenoscanner database to exclude single nucleotide polymorphisms (SNPs) associated with confounding factors or outcomes. Our forward Mendelian randomization analysis suggests that there is no causal relationship between UA levels/gout from different populations and the risk of AF [IVW OR 1.03, 95% CI: 0.97-1.08; p = 0.335; IVW OR 0.99, 95% CI: 0.97-1.02; p = 0.583; and IVW OR 1.07, 95% CI: 0.84-1.37; p = 0.575], respectively. We did not detect significant heterogeneity or potential pleiotropy, and we also excluded the possibility of weak instrumental variables. Furthermore, we did not find any reverse causal effects of AF on sUA levels and gout risk. Our findings challenge the widely held belief that lowering urate levels is uniformly effective in reducing the risk of atrial fibrillation (AF). Our study fails to substantiate the existence of a causal link between uric acid (UA) levels or gout and the development of AF, regardless of direction.