Abstract
BackgroundOlfactory dysfunction is associated with severe brain atrophy and cognitive impairment in Parkinson’s disease. However, it remains unknown whether an inability to identify particular odors is associated with physical performance, cognitive function, and/or brain atrophy in community-dwelling older adults.MethodsIn this cross-sectional study, 44 community-dwelling older adults were included (14 males, 30 females; mean age: 72.4 ± 5.7 years, range: 63–85 years). The Odor Stick Identification Test for Japanese, consisting of 12 odors, was used to examine olfaction. Subjects also completed physical performance (lower limb function, balance, and gait speed) and cognitive function (global cognition, logical memory, and the Trail Making Tests). Additionally, magnetic resonance imaging was used to investigate brain atrophy in the bilateral medial temporal area (MTA) and whole gray matter using the voxel-based specific regional analysis system for Alzheimer’s disease.ResultsTotal olfaction was not significantly associated with physical performance, cognitive function, or brain atrophy. However, MTA atrophy was associated with an inability to identify Japanese orange (B: − 0.293; β: − 0.347; p < .05) after adjusting for age and sex (R2: 0.328; adjusted R2: 0.277). Subjects who were unable to identify Japanese orange (n = 30) had worse MTA atrophy than those who were able to identify Japanese orange (n = 14), even after adjusting for covariates (p < .05).ConclusionsTotal olfaction was not associated with physical performance, cognitive function, or brain atrophy. However, an inability to identify Japanese orange odor was independently associated with mild MTA atrophy among community-dwelling older adults.
Highlights
Parkinson’s disease (PD) and [1] Alzheimer’s disease (AD) are well known neurodegenerative diseases
We investigated the degree of brain atrophy using voxel-based specific region analysis for AD (VSRAD) Advance 2 software (Eisai, Tokyo, Japan)
analysis of covariance (ANCOVA) was used to examine the effects of independent covariates on atrophy of the medial temporal area among groups in adjusted models (model A: adjusted for age, sex, body mass index, Geriatric Depression Scale (GDS), diabetes mellitus, hyperlipemia, and hypertension; model B: adjusted for model A, global cognition, Wechsler Memory Scale-Revised (WMS-R) Logical Memory Immediate (LM-I), The Trail Making Test (TMT)-A, and TMT-B; model C: adjusted for model B, chair stand, one leg standing test, preferred gait speed, and maximal gait speed; model D: adjusted for model C and whole gray matter atrophy)
Summary
Study population The geographic area of this cross-sectional study was “Island City” (Higashi-ku, Fukuoka, Japan; known as the Fukuoka Island City Study) [12, 13]. ANCOVA was used to examine the effects of independent covariates on atrophy of the medial temporal area among groups in adjusted models (model A: adjusted for age, sex, body mass index, GDS, diabetes mellitus, hyperlipemia, and hypertension; model B: adjusted for model A, global cognition, WMS-R LM-I, TMT-A, and TMT-B; model C: adjusted for model B, chair stand, one leg standing (with open eyes) test, preferred gait speed, and maximal gait speed; model D: adjusted for model C and whole gray matter atrophy). Multiple regression (stepwise) analysis was performed to analyze whether physical performance, cognitive function, and brain atrophy were associated with the ability to identify particular odors, as independent covariates This analysis consisted of three steps: step A: forced entry of covariates (age and sex); step B: stepwise entry of covariates (height, weight, body mass index, GDS, diabetes mellitus, hyperlipemia, and hypertension); and step C: stepwise entry of predictor variables (Indian ink, wood, menthol, Japanese cypress, perfume, rose, Japanese orange, condensed milk, roasted garlic, curry, cooking gas, and fermented beans/sweaty socks). Analyses were performed using SPSS v26 for Windows (IBM Corp., Armonk, NY)
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