Our new study added approximately 2,500 new controls from the British 1958 Birth Cohort to the 1,500 described above, and compared these with a new group of approximately 4,000 British cases from the JDRF/WT DIL collection. All cases and controls were resident in Great Britain. To minimize the effects of population structure, the case-control comparisons in the WTCCC and T1DGC studies have been stratified by the 12 regions of Great Britain5,7. Sample exclusions in the genome-wide studies are discussed in Supplementary Methods.
