Background: Olfactory 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.
Methods: In 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.
Results: Total 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).
Conclusions: Total 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.
Keywords: Amygdala; Entorhinal cortex; Hippocampus; Olfactory dysfunction; Orange.
© 2021. The Author(s).