Olfactory dysfunction as a marker of neurodegenerative disease in older adults

BACKGROUND: Early identification of neurodegenerative disorders in older adults remains a major challenge in geriatric clinical practice. Olfactory dysfunction is a common feature of several neurodegenerative disorders, particularly synucleinopathies, where it often precedes motor and cognitive symptoms, whereas in primary tauopathies olfactory function is usually preserved or only mildly impaired. AIMS: This study aimed to evaluate the diagnostic utility of the 12-item Sniffin' Sticks Test (SST-12) for identifying neurodegenerative disease in older adults. METHODS: A total of 120 individuals were included: 72 with synucleinopathies, 23 with tauopathies, and 25 healthy controls. Olfactory function was assessed using the SST-12. Group differences were analyzed using ANOVA, Fisher's exact test, and post hoc procedures. Diagnostic accuracy was evaluated by ROC analysis. RESULTS: Anosmia occurred in 58.3% of synucleinopathy patients and 65.2% of tauopathy patients but was absent in controls (p < 0.0001). Women performed better on several items, while an age effect was observed only for odor T5 (banana) (p = 0.011). Subjective olfactory complaints had limited diagnostic value. The full SST-12 showed good accuracy in distinguishing patients from controls (AUC = 0.818; 95% CI 0.744-0.891). A shortened nine-odor version achieved slightly higher accuracy (AUC = 0.844; 95% CI 0.777-0.912). No significant difference was observed between synucleinopathies and tauopathies, including after adjustment for age and sex. DISCUSSION: These findings support the clinical usefulness of brief olfactory testing in older adults and highlight the potential of selected odor subsets to improve screening efficiency. CONCLUSION: The SST-12 is a sensitive and practical tool for detecting olfactory dysfunction in neurodegenerative disorders. Brief olfactory screening may represent a useful addition to routine geriatric assessment.