Objective: To examine whether individuals at increased risk of developing Parkinson’s disease (PD) show specific cognitive impairments suggestive of progression towards PD.

Background: Olfactory deficits (hyposmia) are one of the most common non-motor symptoms of Parkinson’s disease. Hyposmia often appears before PD has been clinically diagnosed and can be an early, pre-clinical marker of the disease. The presence of hyposmia also increases the probability of future PD in at-risk populations such as first-degree relatives of PD patients. However, as hyposmia is not specific to PD, additional markers are needed in order to identify PD in its early stages. Cognitive impairments in the domains of working memory, processing speed, and executive function have been shown to be present in PD patients. Yet, it is unclear whether these signs are present in individuals at risk of PD as well.

Method: Patients with early-stage PD (n = 26), age- and sex-matched healthy controls (n = 26), and an at-risk group (n = 30) including hyposmic first-degree relatives of PD patients and unrelated hyposmic individuals were included in this study. Hyposmia was determined with the University of Pennsylvania Smell Identification test (UPSIT). Participant groups were compared on a battery of neuropsychological tests, which included verbal and spatial working memory, processing speed, and executive function tasks.

Results: PD patients exhibited deficits in semantic fluency and processing speed compared to controls. Both PD patients and the at-risk group with hyposmia showed significant impairments in verbal working memory compared to controls (p < .05). There were no significant differences between hyposmic first-degree relatives and hyposmic non-relatives.

Conclusion: Early-stage PD patients show deficits in multiple cognitive domains. The combination of hyposmia and impaired verbal working memory could indicate the progression towards PD, and may have implications in clinical diagnostic procedures for persons considered at-risk of developing PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/comparisons-between-parkinsons-disease-patients-and-at-risk-individuals-can-olfactory-deficits-and-cognitive-measures-serve-as-preclinical-markers/