All stage 1 study effect estimates were corrected using genomic control40 and were oriented to the forward strand of the NCBI build 36 reference sequence of the human genome, consistently using the alphabetically higher allele as the coded allele. Study-specific lambda estimates are shown in Supplementary Table 1. The pooled effect-size estimate and s.e.m. were computed using inverse variance weighting, and genomic control was applied to the pooled effect-size estimates. To describe the effect of imperfect imputation on power, we report ‘N effective’, the sum of the study-specific products of the sample size and the imputation quality metric. Meta-analysis statistics and figures were produced using R version 2.7.0.
