SNP heritability studies of AD have demonstrated its highly polygenic nature. Risk profile scoring analyses support the polygenicity of AD by demonstrating that scores generated using nominally significant SNPs from GWAS significantly predict risk in independent samples. Thus far, SNP heritability studies have estimated the heritability from common SNPs to be up to 23%, which with better-powered samples could increase. Thus, SNP heritability accounts for roughly half of the heritability of AD estimated in family studies, which is in line with estimates for phenotypes such as height, where the SNP heritability was estimated at 45%, about half of the overall heritability estimated in twin studies of 80% (Yang et al., 2010). To date, all such studies of AD have used comparatively small samples. Studies in larger samples, potentially available through collaborations such as the PGC Addictions group and GSCAN, should provide more accurate estimates of the SNP heritability.
