Noticeably, the leftmost cluster (i.e., cluster number 1) was the cluster with the maximum percentage of AD (84% AD, 16% MCI, 0% CN), the lowest MMSE score (21.2 ± 4.0), the highest prevalence of APOE4 carriers (71%), and the highest level of abnormal AB1-42, T-TAU, and P-TAU proteins in the CSF, while the rightmost cluster (i.e., cluster number 3) contained primarily CN (5% AD, 26% MCI, 69% CN) and had the highest MMSE score (27.5 ± 2.4), the lowest prevalence of APOE4 carriers (24%), and the lowest level of abnormal AB1-42, T-TAU, and P-TAU proteins in the CSF. This evidence concerns the gene APOE and Alzheimer disease.