HDAC4 and Cognitive impairment: In the anosmic group, the expression of Procollagen, type I, α1 (COL1A1 up-regulated in cognitive impairment), Aquaporin-4 (AQP4 plays a role in the proinflammatory features of astrocytes), Fibrinogen gamma chain (FGG regulate nervous system functions), ADP-Ribosyl Cyclase 1(CD38 cognition and spatial memory related), and Histone deacetylase 4 (HDAC4 cognition and spatial memory related) was significantly increased (P < 0.0001; P = 0.001; P = 0.0005; P = 0.0003; P = 0.0038).