Worse Odor Identification is Associated with Poorer Cognitive Function in pre-MCI Individuals: A Meta-analysis
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Introduction
Odor identification correlates with Alzheimer’s disease (AD) biomarkers, and its decline may emerge before measurable cognitive deficits—as early as the subjective cognitive decline (SCD) stage. We aimed to compare odor identification between SCD and cognitively normal (CN) stages and investigate whether cognitive differences moderate olfactory deficits.
Methods
A systematic search of four databases identified studies assessing olfactory identification and cognitive screening in individuals aged 50 years or older. A random-effects meta-analysis was performed on 11 studies (660 SCD, 574 CN).
Results
Individuals with SCD exhibited lower olfactory identification scores compared to CN participants (SMD = −0.67, 95%CI [−1.31, −0.03], p = .04). Meta-regression analyses indicated that larger cognitive differences between groups were associated with more pronounced olfactory deficits ( β = −1.79, p = .02).
Discussion
Worse cognition in pre-MCI individuals is associated with impaired odor identification, supporting the potential role of odor identification as a screen for AD biomarkers and future cognitive decline.
