Saliva-based Genotyping Protocol

Saliva samples were collected from all enrolled subjects using the Oragene DNA collection kit, and DNA extraction was performed (DNA Genotek, Ontario, Canada). Genotyping was carried out using the Omni Express 700k Illumina Chip, including only samples and sites with call rate ≥0.99 (43,655 variants excluded), Hardy-Weinberg Equilibrium p-value ≥1*10^–6 (3,153 variants excluded), and minor allele frequency (MAF) ≥ 0.01 (18 variants excluded). Imputation was performed using MINIMAC v4 (Howie et al., 2012 (link)) to Haplotype Reference Consortium imputation panel version r1.1 (McCarthy et al., 2016 (link)). All data were aligned to the human reference genome build 37 (GRCh37). After imputation, SNPs with Info Score <0.4 (13626943 variants excluded) and MAF <0.01 (40,203 variants excluded) were discarded from statistical analyses. A total of 7783479 SNPs were analysed.