around the same time each found only one or two of the loci, with little overlap across these smaller studies, consistent with each having modest power for the larger set of loci. Further, recent meta-analyses of 4,539 cases for type 2 diabetes and 3,230 for Crohn's disease have been needed to discover further loci with estimated effect sizes in the range 1.1–1.2. Even for a disease not previously studied by GWA, studies with fewer than 2000 cases and 2000 controls will have low power, except in special circumstances, for example if there are loci with larger effect sizes than has been typical across many other diseases.
