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Updated: May 16, 2025
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Simple and Computer-assisted Olfactory Testing for Mice
Published on: June 15, 2015
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Lower Odor Identification in Subjective Cognitive Decline: A Meta-analysis
Benoît Jobin1,2,3, Coline Zigrand4,5, Johannes Frasnelli2,6,5
1Department of Psychology, Université du Québec à Trois-Rivières, 3351 Boulevard des Forges, Trois-Rivières, QC G9A 5H7, Canada.
Summary
Odor identification is lower in individuals with subjective cognitive decline (SCD), suggesting olfactory deficits may precede cognitive impairment. This finding supports using odor identification tests for early Alzheimer's disease (AD) screening.
Area of Science:
- Neuroscience
- Gerontology
- Olfactory Research
Background:
- Odor identification decline is linked to Alzheimer's disease (AD) biomarkers.
- Olfactory deficits may precede measurable cognitive decline, appearing even in the subjective cognitive decline (SCD) stage.
Purpose of the Study:
- To compare odor identification abilities between individuals with SCD and cognitively normal (CN) individuals.
- To investigate if cognitive differences influence olfactory deficits in these groups.
Main Methods:
- A systematic literature search was conducted across four databases.
- A random-effects meta-analysis synthesized data from 11 studies involving 660 SCD and 574 CN participants aged 50+.
Main Results:
- Individuals with SCD demonstrated significantly lower odor identification scores compared to CN participants (SMD = -0.67, p = .04).
- Meta-regression indicated that olfactory deficits in SCD occurred independently of significant cognitive differences, with no consistent association between greater cognitive decline and greater olfactory impairment.
Conclusions:
- Reduced odor identification is observed in individuals with SCD, suggesting olfactory decline can emerge prior to overt cognitive impairment.
- Odor identification may serve as a valuable, non-invasive screening tool for early detection of Alzheimer's disease risk.
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