APOE and Cognitive impairment: Among them, the gene encoding apolipoprotein E (ApoE) is located on chromosome 19 and has three isoforms, ApoE2, ApoE3 and ApoE4, which are expressed by alleles ɛ2, ɛ3 and ɛ4, respectively, ApoE may affect the metabolic deposition of amyloid β (Aβ) peptides, lipid metabolism, inflammatory response, and other mechanisms that cause cognitive impairment in the body through increased toxicity and/or loss of neuroprotective effects [9].