In 1993, Saunders et al. (Strittmatter et al., 1993) and Strittmatter et al. (Kim et al., 2003) published landmark papers linking the ApoE ε4 allele to the development of late-onset, sporadic AD.Depending on the gene dose of the e4 alleles, the presence of the e4 allele raises the risk of AD from 20% to 90% and lowers the age of onset from 84 to 68 years. Here, APOE is linked to Alzheimer disease.