Genotype imputation
All missing genotypes were imputed in order to examine any potential effect of the unmeasured variants. We used 1,000 Genomes ASN Phase I integrated variant set release (v3) in National Center for Biotechnology Information (NCBI) build 37 (hg19) as a reference panel, along with PLINK software (version 1.07) [20] for strand alignment, SHAPEIT2 [21] for phasing, and IMPUTE2 [22] for the imputation procedure. Only variants with Info Score ≥0.9 were included in the final count, resulting in a total of 4,414,664 SNPs, which were either genotyped or imputed with high confidence.