All participants provided informed consent. There were 1238 individuals meeting DSM-IV AD diagnosis from 591 families. Controls were recruited in the Northern Ireland from volunteers of blood donating (88.5%) and in Ireland from national police force and army reserve. Controls were screened and their samples excluded if they reported a history of heavy drinking or problematic alcohol use. In the present case-control study design, we included 530 controls and 575 independent AD cases from the IASPSAD families (for detailed case and control sample description see Kuo et al., 2008). Samples were selected based on high yield of high quality DNA for genotyping and only one case per family was included.
