Limitations of the study include (1) some patients with AD and MCI, may also suffer from other health conditions (e.g., CVD and/or EMD); (2) phenotypic heterogeneity with high variation could result in the inconclusive accentuation of biomarkers (ApoE ε4 allele, ACE1, and APO proteins). The gene discussed is AOPEP; the disease is Alzheimer disease.