SNP imputation
In each GWAS data point, imputation analysis was performed using the IMPUTE reference HapMap Asian (Japanese [JPT]/Han Chinese [CHB]) population panel, based on NCBI build 36 and dbSNP build 129. Of these, in each cohort, we dropped SNPs with a posterior probability score < 0.90, high genotype information content (info < 0.5), Hardy-Weinberg equilibrium (HWE) (p < 1 × 10-7), SNP missing rate > 0.1, and minor allele frequency (MAF) < 0.01. In the former analysis, only imputed SNPs that satisfied the genomewide SNP quality control criteria were considered.