Logistically, one important challenge in executing our study was coordinating analysis strategies and phenotype modeling across 15 different cohorts, each with specific genotyping, phenotyping, trait modeling and analytical strategies. Given this challenge, we decided to start by carrying out a meta-analysis of results from study-specific analyses, relying only on knowledge of the BMI-increasing allele and P value for each study, before completing a uniform analysis across all studies. Notably, we found very similar results between the study-specific analysis, in which different adjustments for covariates and analytical procedures were performed in different studies, and the uniform analysis, in which these procedures were harmonized across all studies (Supplementary Fig. 2). Thus, at least for this phenotype, the association analysis is robust enough to differences in phenotypic modeling so that differences in study design or analytic strategies do not preclude discovery of new loci using meta-analysis.
