AQP4 and Cognitive impairment: When the patients were categorised into three groups—with a diagnosis of neurodegenerative disease, with cognitive deficits but without a diagnosis of neurodegenerative disease, and controls—the AQP4 levels were significantly higher in the neurodegenerative group with respect to controls (Kruskal–Wallis test: p = 0.019) and the same result was obtained when only two groups were considered, i.e., the neurodegenerative (mean = 337.9 ± 24.9 pg/ml) versus not neurodegenerative subjects (mean = 243.1 ± 15.3 pg/ml).