Flavour perception in Alzheimer's disease: A systematic review of olfactory and gustatory assessment methods

Disruptions in flavour perception, due to olfactory dysfunction and gustatory dysfunction, may serve as early indicators of Alzheimer's disease and contribute to reduced quality of life. Flavour perception is a multisensory process, yet no standardised tools currently exist to assess it comprehensively in Alzheimer's disease. This systematic review examined current olfactory and gustatory assessments used to evaluate flavour function in individuals with Alzheimer's. Six studies met the inclusion criteria, encompassing 471 participants, including 161 with Alzheimer's. Olfactory function was most often assessed with the Sniffin' Sticks test, while gustatory function was typically evaluated using Taste Strips. While olfactory dysfunction was consistently reported across studies, evidence for gustatory impairment was less uniform, reflecting methodological variability in taste assessment procedures. Only one study used a culturally adapted test, and none assessed umami. However, the small number of studies, heterogeneity in methodology, and limited cultural adaptation constrain the generalisability of these findings. These findings highlight the need for a culturally adaptable, combined flavour assessment tool that minimises cognitive and linguistic demands to support early detection and monitoring of Alzheimer's disease.