Changes in Taste Perception in Patients with Minor and Major Cognitive Impairment Linked to Alzheimer’s Disease Recorded by Gustatory Evoked Potentials

Background: The need for early diagnosis biomarkers in Alzheimer’s disease (AD) is growing. Only few studies have reported gustatory dysfunctions in AD using subjective taste tests. Objective: The main purpose of the study was to explore gustatory functions using subjective taste tests and recordings of gustatory evoked potentials (GEPs) for sucrose solution in patients with minor or major cognitive impairment (CI) linked to AD, and to compare them with healthy controls. The secondary objective was to evaluate the relationships between GEPs and the results of cognitive assessments and fasting blood samples. Methods: A total of 45 subjects (15 healthy subjects, 15 minor CI patients, 15 major CI patients) were included to compare their gustatory functions and brain activity by recording GEPs in response to a sucrose stimulation. CI groups were combined in second analyses in order to keep a high power in the study. Correlations were made with cognitive scores and hormone levels (ghrelin, leptin, insulin, serotonin). Results: Increased P1 latencies and reduced N1 amplitudes were observed in minor or major patients compared to controls. GEPs were undetectable in 6 major and 4 minor CI patients. Thresholds for sucrose detection were significantly higher in the major CI group than in controls or the minor CI group. No correlation was found with hormone levels. Conclusions: The cortical processing of sensory taste information seems to be altered in patients with minor or major CI linked to AD. This disturbance was identifiable with subjective taste tests only later, at the major CI stage.