Statistical analysis

The conventional inverse variance weighted method [14] was used to estimate the associations of genetically predicted 1 s.d. increase in each adiposity measure with odds ratio of gout and serum urate concentrations (in mg/dl). The weighted median and Mendelian randomization Egger (MR-Egger) regression methods were used as sensitivity analyses [14]. The weighted median method provides consistent estimates if at least 50% of the weight comes from valid instrumental variables [14]. The MR-Egger method can be used to identify and adjust for directional pleiotropy [14, 15]. Bias caused by pleiotropy is analogous to small study bias in a meta-analysis, where small studies with less precise estimates tend to report larger estimates than larger studies with more precise estimates. Heterogeneity between SNPs was tested by using the I² statistic and Cochran’s Q test [16]. A threshold of statistical significance of P < 0.0125 (P = 0.05/4) was used to reflect testing of two adiposity measures (BMI and WHR adjusted for BMI) and two outcomes (gout and serum urate concentrations). Stata (version 14.1; StataCorp, College Station, TX, USA) was used for all analyses.