Abstract
BackgroundPatients with Alzheimer’s disease dementia (ADD) are thought to exhibit taste disorders; however, this has not been extensively studied. We investigated gustatory functions and factors affecting taste in patients with ADD or mild cognitive impairment (MCI) and in non-demented controls (NDCs) and evaluated associations between cognitive impairment and gustatory functions.MethodsWe recruited 29 patients with ADD, 43 with MCI, and 14 with NDCs. We obtained medical and medication history, measured salivary secretion volumes, and performed cognitive function tests, blood tests, whole-mouth gustatory tests, and dietary and gustatory questionnaires.ResultsPatients with ADD showed significantly higher recognition threshold values than NDCs (p < 0.05). Many individuals did not recognize umami at the maximum concentration, and this happened more frequently in patients with ADD or MCI than in NDCs. Evaluation items other than cognitive function tests did not show significant differences among the groups, but many individuals had decreased salivation, low serum zinc levels, and were on multiple medications. We found a significant correlation between recognition threshold and age (r = 0.229, p < 0.05) and cognitive function test score (r = 0.268, p < 0.05).ConclusionsPatients with ADD showed impairment of gustatory function. Gustatory impairment in patients with MCI could not be confirmed. However, many individuals with MCI did not recognize umami, either. Our results suggest that taste disorders in elderly people with cognitive decline occur independently of factors affecting taste such as salivation, zinc levels, or prescription drugs.Trial registrationThe study was registered in the UMIN Clinical Trials Registry on February 10, 2017, with reference number UMIN000026087.
Highlights
Patients with Alzheimer’s disease dementia (ADD) are thought to exhibit taste disorders; this has not been extensively studied
The type Dementia Assessment Scale (TDAS) scores were significantly higher in patients with ADD than in those with mild cognitive impairment (MCI) or non-demented controls (NDCs)
At the detection threshold of sweet, we found a significant increase in the ADD and MCI groups compared with the NDC group
Summary
Patients with Alzheimer’s disease dementia (ADD) are thought to exhibit taste disorders; this has not been extensively studied. Gustatory tests include the filter-paper disc method [12], the taste-strip test [13, 14], electrogustometry [12, 15], and the whole-mouth gustatory test [16, 17]. A study based on the filter-paper disc method and electrogustometry has suggested that patients with ADD may exhibit taste disorder concomitantly with brain atrophy and neurodegeneration [8]. Another study using taste strips reported reduced taste function in patients with mild cognitive impairment (MCI), which is a pre-dementia state [9]. Other reports using filter-paper discs have found no deterioration of the taste function in patients with ADD [18], and there was no detection threshold disorders for sweet and sour tastes in whole-mouth gustatory tests [19]. Few studies have examined taste in patients with MCI, and, it is unclear whether taste function is impaired in these patients
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