Twelve independent genome-wide significant loci were identified by LD clumping and merging loci within 400 kb (Supplementary Information). In two of these loci a second index variant persisted after LD clumping. The two putative secondary signals were evaluated by considering analysis conditional on the lead index variant in each locus. In each cohort, logistic regression was performed with the imputed genotype dosage for the lead index variant included as a covariate. All covariates from the primary GWAS (e.g. principal components) were also included. The conditional association results were then combined in an inverse-variance weighted meta-analysis.
