Abstract
Alzheimer’s disease (AD) patients exhibit olfactory dysfunction. However, the olfactory declineti precise nature is not fully understood. One hundred patients (60 AD, 28 amnestic mild cognitive impairment (aMCI), 12 Normal) were enrolled. All participants underwent olfactory function testing using an odour stick identification test for Japanese (OSIT-J). OSIT-J scores were significantly correlated with recall. We classified OSIT-J odorants into three groups: Category I, odorants that were difficult for normal aged subjects to identify; Category II, odorants that became harder to accurately identify with cognitive decline; and Category III, odorants that even AD patients could identify. We defined a “cognitive subset” consisting of six Category II OSIT-J odorants (perfume, rose, Japanese cypress, curry, India ink and gas leak odour). The ability to identify “cognitive subset” odours was significantly better indicator of cognitive status than the ability to identify “non-cognitive subset”, which consisted of the six remaining items. The ability to identify the gas leak odorant was decreased early in the aMCI stage, suggesting a need to reconsider the odours used to signal gas leaks. The “cognitive subset” would provide a more convenient and effective biomarker for diagnosing dementia in clinical settings.
Highlights
Alzheimer’s disease (AD) has long been reported to be associated with olfactory dysfunction[1,2,3,4]
ANOVA comparisons of the Normal, amnestic mild cognitive impairment (aMCI) and AD groups found no significant differences in age, Barthel Index, instrumental activities of daily life (IADL) or 15-item Geriatric Depression Scale scores (GDS15). χ square analysis revealed no
Catetory I – odorants that were difficult for normal aged subjects to identify, including menthol, condensed milk, Japanese orange and wood;
Summary
Alzheimer’s disease (AD) has long been reported to be associated with olfactory dysfunction[1,2,3,4]. The relationship between olfaction and specific neural substrates of cognitive function has not been well explored This relationship may be attributable to the neurofibrillary tangle in the entorhinal cortex and hippocampus[9] and cholinergic system dysfunction[10]. We strongly believe that olfactory testing is a clinically useful non-invasive tool for evaluating disease state in elderly people. It provides much information about dementia and can predict progression from amnestic mild cognitive impairment (aMCI) to AD11, but little is known about the precise nature of AD-associated olfactory decline. To investigate the heterogeneity of AD-associated olfactory decline with these objectives, we performed olfactory tests and cognitive examinations with AD patients
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