In one of the largest AD GWAS to date, Heath et al. (2011) included 8,754 European ancestry family members (2,062 AD cases) and 3,393 Australian population-based controls to test the association of 300,000 SNPs with three phenotypes: AD case-control status, a quantitative AD factor score, and a quantitative “heaviness of drinking” factor score. No GWS loci were identified for any of the phenotypes, and the authors were unable to replicate any of the SNPs identified in previous GWAS (Treutlein et al., 2009; Bierut et al., 2010; Edenberg et al., 2010). This study showed that effects, as expected, are very small (0.15–0.25% of the variance in AD risk), and that larger samples are needed to detect them.
