Among them, the apolipoprotein E (APOE), in particular the ε4 allele, PICALM, CLU, ABCA7, and CR1 are the most important genes being associated with AD risk factor or the progression from MCI to AD [20, 21, 22, 23, 24, 25, 26, 27]. This evidence concerns the gene APOE and Alzheimer disease.