Objective: Using a larger sample size compared to our previous study, we evaluated the relationship between olfactory dysfunction based on the University of Pennsylvania Smell Identification Test (UPSIT) to the clinicopathological findings in PD (n=41), incidental Lewy Body Disease (n=47), and controls with no neurodegenerative disease (n=137).

Background: Measuring olfactory dysfunction shows promise as one of a number of non-motor biomarkers that can be used to detect prodromal Parkinson’s disease (PD).

Method: This study was conducted through the Arizona Studying of Aging and Neurodegenerative Disease (AZSAND). We selected individuals who had an UPSIT score completed antemortem and were clinicopathologically diagnosed with PD, ILBD, or control. Various measures included density of Lewy type synucleinopathy (aSyn) in the olfactory bulb tract, and other nuclei involved with olfaction. Cases and controls were analyzed using one-way analysis of variance with pairwise contrasts.

Results: Compared to controls (mean 27.8, SD 6.0), the mean UPSIT scores were lower for PD (15.8, SD 6.0, p<.001) and ILBD (24.1, SD 8.6, p<.001). The sensitivity for detecting ILBD based on a cutoff score of <23 (23/47) was 48.9%. The specificity for detecting a control was 79.6% with a cutoff >23 (109/137).

Conclusion: These findings, which included a larger sample size from our previously published studies, confirmed that individuals with autopsy confirmed PD and ILBD have lower UPSIT scores compared to controls. These data add to the growing body of evidence supporting early olfactory dysfunction as a prodromal biomarker for the risk of developing Parkinson’s disease.

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