Objective: To determine the longitudinal differences in cognitive tests in participants with Parkinson’s disease (PD), and the neuropsychological tests most sensitive to change over and above ageing.

Background: Cognitive impairment is common in PD, with 80% cumulatively developing dementia (PDD) over 20 years. However, it is unclear which neuropsychological tests are most sensitive to change over time in PD, which are predictive of dementia, and how this differs to ageing.

Method: Newly diagnosed PD patients (n=212) and age matched controls (n=99) completed a schedule of clinical and neuropsychological tests as part of the ICICLE-PD study and returned at 18 month intervals over 72 months. Global cognition was measured using the Montreal Cognitive Assessment (MoCA). Detailed cognitive assessments of executive function, attention and memory were completed, comprising verbal fluency scores and selective tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB) and Cognitive Drug Research (CDR) computer tests. Changes in cognition across time points were determined using linear mixed effects models, adjusting for age, sex, years of education, depression and motor severity.

Results: At 72-month evaluation, 105 (49.6%) PD subjects and 66 (66.7%) returned. Cumulatively 45 (21.2%) participants developed PDD. Non-completing participants were significantly older, had higher baseline motor severity and lower baseline MoCA scores (p<0.05 for all). Adjusting for covariates, PD participants’ rate of change was significantly faster than controls for global cognition, phonemic and semantic fluency scores, choice reaction time (CRT), CRT accuracy and power of attention (p<0.05 for all). PD subjects showed significant changes over time in global cognition, phonemic and semantic fluency scores, mean CRT, attention variability and continuity of attention (p<0.05 for all). Comparing rate of change in participants who did and did not develop PDD, PDD had a significantly faster rate of decline in global cognition, verbal fluency, memory, CRT, attention accuracy and attentional variability (p<0.05 for all).

Conclusion: Selected measures for global cognition, executive function and attention were sensitive to change in PD subjects over time, independent of normal ageing. Our findings suggest that future studies should consider using specific verbal fluency and CDR attention tests to detect changes in PD subjects.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/neuropsychological-changes-over-the-first-6-years-of-parkinsons-disease-in-the-icicle-pd-cohort/