Nevertheless, the major driver of AD in the general population is the common apolipoprotein E ɛ4 variant (APOE ɛ4), which is associated with an elevated risk of developing dementia, i.e., 51–95% in APOE ɛ4/ɛ4 and 22–90% in APOE ɛ4/- [26, 27] and a mean age at dementia onset of 73–74 years in APOE ɛ4/ɛ4 and 75–82 in APOE ɛ4/- [28, 29]. This evidence concerns the gene APOE and Alzheimer disease.