Cognitive and Motor Function in Long-Duration PARKIN-Associated Parkinson Disease

Importance Data on the long-term cognitive outcomes of patients with PARKIN -associated Parkinson disease (PD) are unknown but may be useful when counseling these patients. Objective Among patients with early-onset PD of long duration, we assessed cognitive and motor performances, comparing homozygotes and compound heterozygotes who carry 2 PARKIN mutations with noncarriers. Design, Setting, and Participants Cross-sectional study of 44 participants at 17 different movement disorder centers who were in the Consortium on Risk for Early-Onset PD study with a duration of PD greater than the median duration (>14 years): 4 homozygotes and 17 compound heterozygotes (hereafter referred to as carriers) and 23 noncarriers. Main Outcomes and Measures Unified Parkinson Disease Rating Scale Part III (UPDRS-III) and Clinical Dementia Rating scores and neuropsychological performance. Linear regression models were applied to assess the association between PARKIN mutation status and cognitive domain scores and UPDRS-III scores. Models were adjusted for age, education, disease duration, language, and levodopa equivalent daily dose. Results Carriers had an earlier age at onset of PD ( P P  = .004) at time of examination than noncarriers. They performed better than noncarriers on the Mini-Mental State Examination ( P  = .010) and were more likely to receive lower scores on the Clinical Dementia Rating ( P  = .003). In multivariate analyses, carriers performed better than noncarriers on the UPDRS-III ( P  = .02) and on tests of attention ( P  = .03), memory ( P  = .03), and visuospatial ( P  = .02) cognitive domains. Conclusions and Relevance In cross-sectional analyses, carriers demonstrated better cognitive and motor performance than did noncarriers with long disease duration, suggesting slower disease progression. A longitudinal follow-up study is required to confirm these findings.