The APOE ε4 allele (comprising the T allele of rs429358 and the C allele of rs7412 in cis) serves to reduce the age of onset of Alzheimer disease from 78.4 years in patients lacking the allele, to 75.3 in heterozygous carriers to 72.9 in carriers of two APOE ε4 alleles (Sando et al. 2008). This evidence concerns the gene APOE and Alzheimer disease.