Thousands of genetic loci associated with hundreds of complex traits have been identified through GWAS and as sample sizes continue to increase, more loci will be discovered. Although the cost of GWAS has dropped, lack of financial resources is still the limiting factor for generating new data. Most GWAS have been conducted in case-control studies, and this has led to the creation of disease-specific consortia in which power can be maximized. However, there is usually only one disease phenotype available from these cases, and little capacity to follow cases or controls to collect information on additional phenotypes that develop over time. Cohort studies are designed to collect multiple endpoints on individuals, but often suffer from limited power for a specific disease. To maximize the utility of existing cohort data resources, it is important to explore associations with additional traits and outcomes that have been collected for individuals in multiple cohorts. In particular, the accumulation of GWAS data within large cohorts with rich environmental and outcome data creates new opportunities to assess novel hypotheses. In addition, cohort studies provide unique opportunities
