To improve the robustness of the proteomic results, intersections between bridge proteins in Cluster 4/Cluster 5 and DEPs between two groups of samples were defined as key proteins (Figure 8), including C7 (in Cluster 4, showing a consistent upward trend across the progressive steps of cognitive decline), FERMT3, CAP1, ENO1, and ZYX (in Cluster 5, showing a consistent downward trend across the progressive steps of cognitive decline). Here, ZYX is linked to Mental deterioration.