The emergence of genome-wide association studies (GWAS) has provided an opportunity to employ an unbiased approach to identify additional genes related to AD. Prior GWAS have focused on the detection of susceptibility genes to AD (Bierut et al., 2010; Edenberg et al., 2010; Gelernter et al., 2014; Treutlein et al., 2009) and related traits (Baik et al., 2011; Heath et al., 2011; Kapoor et al., 2013; Kendler et al., 2011; Schumann et al., 2011; Wang et al., 2013; Wetherill et al., 2014) but none have investigated genes influencing age at onset. In this study we took advantage of a family-based study design in a well-characterized European American (EA) cohort and performed genome-wide Cox proportional hazards analysis to identify genes associated with age at onset of AD. The extended AD families might be enriched for common factors increasing risk for AD, hence providing additional power to identify the genes associated with age at onset of AD. The analysis demonstrated genome-wide evidence of association of age at onset of AD with several novel loci.
