Alcohol intake and risk of systemic lupus erythematosus: a Mendelian randomization study

Objectives This study aimed to examine whether alcohol intake is causally associated with systemic lupus erythematosus (SLE). Methods We performed a two-sample Mendelian randomization (MR) analysis using the inverse-variance weighted (IVW), weighted median, and MR-Egger regression methods. We used the publicly available summary statistics of alcohol intake frequency from the UK Biobank genome-wide association studies (GWASs; n = 336,965) as the exposure and an SLE GWAS consisting of 1311 SLE and 1783 control subjects of European descent as the outcome. Results We selected 20 single nucleotide polymorphisms (SNPs) associated with alcohol intake frequency at genome-wide significance as instrumental variables to improve inference. The IVW method found no evidence to support a causal association between alcohol intake and SLE (beta = -0.413, SE = 0.513, p = 0.421). The MR-Egger regression revealed that directional pleiotropy was unlikely to bias the result (intercept = 0.031, p = 0.582). The MR-Egger analysis found no causal association between alcohol intake and SLE (beta = -1.494, SE = 1.996, p = 0.464). Likewise, the weighted median approach also did not provide evidence of a causal association between alcohol intake and SLE (beta = -0.538, SE = 0.574, p = 0.349). The MR estimates determined using the IVW, weighted median, and MR-Egger regression methods were consistent and results from a "leave-one-out" analysis demonstrated that no single SNP was driving the IVW point estimate. Conclusions The results of MR analysis do not support a causal inverse association between alcohol intake and SLE occurrence.