2048 DNA samples from healthy, unpaid volunteers donating blood at the Irish Blood Transfusion Service and obtained from the Trinity Biobank at Trinity College Dublin were used as controls. Biobank controls were eligible if they denied any problems with alcohol or history of mental illness and if all four grandparents had been born in Ireland, Northern Ireland, Scotland, Wales, or England. Because of the sample source, controls were not formally screened for AD, but the lack of screening was addressed analytically (see GWAS Statistical Analyses). Information about age and sex was available for these subjects.
