Odor Identification Across Time in Mutation Carriers and Non-Carriers in Autosomal-Dominant Alzheimer's Disease.
Level 4 - case-series / case-control
Cross-sectional comparative study (case-control style) of mutation carriers versus non-carriers.
PubMed 38160354 · doi:10.3233/JAD-230618
What was done
Researchers evaluated odor identification performance in 20 mutation carriers (MC) and 20 non-carrier controls (NC) from six families harboring autosomal-dominant Alzheimer's disease (adAD) mutations (APP Swedish, APP Arctic, and PSEN1). Groups were matched on age, sex, education, APOE ε4 status, and estimated years to clinical symptom onset (YECO), though MC had lower Mini-Mental State Examination scores. MC spanned approximately 40 years across the disease spectrum (asymptomatic to dementia), whereas NC were all asymptomatic. Olfactory function was measured using free and cued identification of common odors to derive a total identification score, and results were examined against YECO, episodic memory, and executive function.
What was found
MC showed significantly poorer free and total odor identification performance compared to NC. Four MC were anosmic compared to zero NC. Free and total identification scores were inversely correlated with time to estimated clinical onset (YECO) in both groups. In MC, decline in free odor identification began approximately 10 years prior to estimated clinical disease onset. Odor identification performance was positively associated with both episodic memory and executive function across participants. Specific numerical test scores and statistical values were not reported in the abstract.
Why it matters
The findings indicate that olfactory identification deficits mirror those seen in sporadic Alzheimer's disease and emerge a decade before clinical onset in autosomal-dominant forms, supporting odor identification as a potential non-invasive early biomarker for disease progression.
Limits
The sample size is small (20 carriers and 20 non-carriers) and drawn from only six families across three specific mutations. The disease timeline is based on estimated years to onset rather than longitudinal follow-up within individual patients, and exact test metrics and effect sizes were omitted from the abstract.
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