Association of impaired olfactory identification with prevalent mild cognitive impairment and regional brain atrophy: the Hisayama Study

Toshifumi Minohara; Tomoyuki Ohara; Taro Nakazawa; Naoki Hirabayashi; Yoshihiko Furuta; Mao Shibata; Jun Hata; Takanari Kitazono; Tomohiro Nakao; Toshiharu Ninomiya

doi:10.1111/pcn.13813

Association of impaired olfactory identification with prevalent mild cognitive impairment and regional brain atrophy: the Hisayama Study

Psychiatry Clin Neurosci. 2025 Jul;79(7):370-377. doi: 10.1111/pcn.13813. Epub 2025 Mar 27.

Authors

Toshifumi Minohara^{1

2}, Tomoyuki Ohara^{1

2}, Taro Nakazawa^{1

2}, Naoki Hirabayashi^{2

3}, Yoshihiko Furuta^{2

4}, Mao Shibata^{2

3

5}, Jun Hata^{5

6}, Takanari Kitazono^{4

5}, Tomohiro Nakao¹, Toshiharu Ninomiya^{2

5}

Affiliations

¹ Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
² Department of Epidemiology and Public Health, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
³ Department of Psychosomatic Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
⁴ Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
⁵ Center for Cohort Studies, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
⁶ Department of Health Care Administration and Management, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.

Abstract

Aim: To investigate the association of olfactory identification ability with both the prevalence of mild cognitive impairment (MCI) and regional brain atrophy in a community-dwelling older population.

Methods: A total of 1293 participants without dementia aged 65 years or older underwent a Japanese version of the 4-Item Pocket Smell Test, an assessment of cognitive function, and brain magnetic resonance imaging scanning in 2017-2018. Regional gray matter volumes (GMVs) and white matter lesions volume (WMLV) were estimated using FreeSurfer software. The association of impaired olfactory identification with the presence of MCI and regional GMVs or WMLV was estimated by logistic regression analysis and ANCOVA, respectively. We also assessed the association between impaired olfactory identification and GMVs without regions of interest, using a voxel-based morphometry (VBM) analysis.

Results: Participants with impaired olfactory identification had a significantly higher likelihood of MCI than those without (odds ratio, 1.99 [95% confidence interval, 1.36-2.91]). In the FreeSurfer analysis, participants with impaired olfactory identification had significantly lower GMVs in the entorhinal cortex, inferior temporal gyrus, amygdala, thalamus, hippocampus, and cingulate gyrus, and higher WMLV than those without. The VBM analysis also showed that impaired olfactory identification was significantly associated with lower volume of the left entorhinal cortex, left amygdala, left hippocampus, bilateral thalami, and bilateral subcallosal areas.

Conclusion: Our findings suggest that cognitive function and brain changes may need to be evaluated in older individuals with impaired olfactory identification, which may reflect the extent of neurodegeneration, WMLV, and subsequent cognitive impairment.

Keywords: atrophy; brain; cognitive dysfunction; cross‐sectional studies; olfaction disorders.

MeSH terms

Aged
Aged, 80 and over
Atrophy / pathology
Brain* / diagnostic imaging
Brain* / pathology
Cognitive Dysfunction* / diagnostic imaging
Cognitive Dysfunction* / epidemiology
Cognitive Dysfunction* / pathology
Cognitive Dysfunction* / physiopathology
Female
Gray Matter* / diagnostic imaging
Gray Matter* / pathology
Humans
Japan / epidemiology
Magnetic Resonance Imaging
Male
Olfaction Disorders* / epidemiology
Olfaction Disorders* / pathology
Prevalence
White Matter* / diagnostic imaging
White Matter* / pathology

Abstract

MeSH terms

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