Objective: To determine which baseline cognitive tests in newly diagnosed participants with Parkinson’s disease (PD) predict conversion to dementia (PDD) within six years.

Background: Cognitive impairment is common in PD, with 80% cumulatively developing PDD. We sought to verify and refine the neuropsychological tests that are predictive of an early PDD in this new incident cohort.

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 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. Dementia was diagnosed using Movement Disorders Society criteria. Impairment on tests were dichotomised: i) at 1SD, 1.5SD and 2SD below control mean scores, and ii) using median scores. Backwards Cox-regression models identified baseline demographic, clinical and neuropsychological predictors of PDD using a data-driven approach and area under the curve (AUC) was calculated.

Results: Cumulatively 45 (21.2%) participants developed PDD over six years. Baseline age, motor severity and APO-E4 genotype predicted PDD (p<0.01). Adjusting for covariates, using 1.5SD cut-offs found impaired fluctuating attention predicted PDD (HR=2.5, p<0.05, AUC=0.76). Applying 2SD cut-offs, fluctuating attention (HR=2.6, p<0.05) and One Touch Stockings (HR=2.6, p<0.05) were significant predictors (AUC=0.75). Median scores of common clinical tests found impaired semantic fluency (animals, HR=3.2, p<0.01), MoCA (HR=5.4, p<0.001) and pentagon copying (HR=3.0, p<0.01) predicted PDD (AUC=0.86). However, the strongest model (AUC=0.93) was identified using median score cut-offs of digit vigilance reaction time (HR=6.9, p<0.01) and accuracy (HR=3.3, p<0.05), MoCA (HR=5.1, p<0.01) and pentagon copying (HR=4.7 p<0.01).

Conclusion: Selected measures for global cognition, executive function and attention significantly predicted the development of PDD. However, the tests most predictive of developing an early dementia are dependent on the type of analysis that is undertaken, but confirms that previously reported cognitive predictors, such as semantic fluency and pentagon copying, hold true for our new cohort. However, more sensitive measures of attention in addition these may have greater predictive power.

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