Meta-analysis was performed with the software META [44]. The fixed effects model, using the inverse variance method, was chosen as all cohorts had the same phenotype and measurement scale. Briefly, the cohort-specific beta estimates were summed together by weighting the cohort-specific beta estimates by the inverse of their variance in order to take into account the contribution of each cohort. In addition, the variances of the cohort-specific beta estimates were first multiplied by the cohort-specific genomic control λ estimates. A total of 8970401 SNPs were included in the meta-analysis (the number of SNPs in the cohort-specific GWAS analyses was 9087865 in FinnTwin, 8829569 in YFS, and 9050503 in FINRISK2007). The genomic control inflation factor (λ) in the meta-analysis was 1.027, while in cohort-specific GWAS they were 1.038 in FinnTwin, 1.016 in YFS, and 1.000 in FINRISK2007.
