As shown in Supplementary Table 1, for all but 2 meta-analyses the respective individual studies included in the meta-analysis had performed imputation of non-genotyped SNPs. The imputation method used different types of hidden Markov models depending on the specific imputation software. Additionally, in all meta-analyses the respective studies used HapMap data (33-35) to impute missing genotypes, except for 2 meta-analyses (1 %), which used exclusively data from the 1000 Genome Project (1), and another one that used data from both HapMap and the 1000 Genome Project. Commercial Affymetrix and Illumina platforms were the most common genotyping platforms used, with Perlegen platforms being used in 23 meta-analyses. The median number of datasets combined through meta-analysis was 9 (IQR, 5-15; range, 2-46). Fixed-effects model had been used in all 139 meta-analyses as the primary method of data synthesis across the different datasets, while additional models had been used in a total of 16 meta-analyses pertaining to random-effects (n=13), Bayesian approaches (n=1), both random-effects and Bayesian approaches (n=1), and P-value based methods (n=1). Fixed-effects models assume that there is a common true genetic
