Objective: To determine the severity of various neuropsychiatric disturbances in drug-naïve Parkinson’s disease (PD) patients with (PD-OD) and without olfactory dysfunction (PD-NOD) compared to healthy controls (HC).

Background: Olfactory dysfunction is one of the earliest signs of synucleinopathy in Parkinson’s disease (PD). The association between olfactory dysfunction and neuropsychiatric manifestations in early-stage drug-naïve PD patients remains unclear.

Method: The study recruited 184 HC, 279 PD-OD, and 144 PD-NOD from the Parkinson’s Progression Markers Initiative database. Olfactory dysfunction was defined by the performance below the age- and gender-recommended cutoffs on the 40-item University of Pennsylvania Smell Identification Test (UPSIT). The Geriatric Depression Scale Score, the MDS-UPRDS Part I Apathy and Hallucination/Psychosis, the State and Trait Anxiety Score, and the Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease Score were used for evaluating various neuropsychiatric disturbances.

Results: The groups had no significant difference in education, duration, or severity of motor symptoms. After adjusting for age and gender, the PD-OD group had higher severity of hallucinations and psychosis than the PD-NOD and HC group; however, there was no difference between the PD-NOD and HC groups on the psychotic features. The severity of apathy, depression, and anxiety did not differ among the two PD groups, but both PD groups had a higher level of these symptoms than the HC group. No difference in impulse control disorder among the three groups.

Conclusion: Olfactory dysfunction is associated with the severity of hallucinations and psychotic symptoms. It may be a biomarker of higher cortical synucleinopathy resulting in the development of psychosis even in the early motor-manifest, drug-naïve PD patients.

References: Morley JF, Cohen A, Silveira-Moriyama L, Lees AJ, Williams DR, Katzenschlager R, Hawkes C, Shtraks JP, Weintraub D, Doty RL, Duda JE. Optimizing olfactory testing for the diagnosis of Parkinson’s disease: item analysis of the university of Pennsylvania smell identification test. NPJ Parkinsons Dis. 2018 Jan 15;4:2.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/olfactory-dysfunction-and-neuropsychiatric-manifestations-in-early-drug-naive-parkinsons-disease/