Unfamiliar Odor Recognition Ability in Subjective Cognitive Decline.

Area of Science:

• Neuroscience
• Gerontology
• Cognitive Psychology

Background:

• Early detection of dementia of Alzheimer's type (DAT) is crucial for timely intervention.
• Olfactory memory deficits are observed in neurodegenerative diseases, but their utility in early DAT detection requires further investigation.
• Existing olfactory tests may be confounded by prior experiences and verbal memory, necessitating the use of unfamiliar stimuli.

Purpose of the Study:

• To explore the relationship between olfactory memory function and early DAT detection using unfamiliar stimuli.
• To develop and evaluate the Olfactory Recognition Test with Unfamiliar Stimuli (ORT-US) for its discriminative power in identifying DAT.
• To minimize confounding factors like previous experiences and verbal memory in assessing olfactory function.

Main Methods:

• A cross-sectional study involving participants classified into healthy control (HC), subjective cognitive decline (SCD), mild cognitive impairment (MCI), and very mild DAT groups.
• The Olfactory Recognition Test with Unfamiliar Stimuli (ORT-US) was administered to assess olfactory memory.
• Analysis of variance (ANOVA) and receiver operator characteristic (ROC) analysis were used to compare ORT-US scores and evaluate discriminative power.

Main Results:

• Significant differences in ORT-US scores were observed only between healthy controls and very mild DAT groups.
• False-alarm scores (misidentifying odors) were significantly different, while hit scores (correctly identifying odors) were not.
• The area under the curve from ROC analysis was unsatisfactory, indicating limited efficacy of odor recognition with unfamiliar stimuli for DAT detection.

Conclusions:

• Olfactory memory function is related to early DAT detection, but odor recognition using unfamiliar stimuli has limited clinical utility.
• The ORT-US demonstrated insufficient discriminative power for effectively identifying individuals with DAT.
• Further research is warranted to explore alternative olfactory-based markers and refine testing methodologies for early DAT detection.