To examine cognitive and functional decline in Parkinson’s disease (PD)

The stability of cognitive status vs. progression to mild cognitive impairment (PD-MCI) or dementia (PDD) is not fully elucidated. Diagnosing PDD depends on functional decline, though this remains controversial in PD-MCI and challenging in PD.  

We conducted clinical and neuropsychological evaluations in a 3-year longitudinal study of PD participants (Time1, n=51; Time 2, n=47; Time 3, n=31). We examined change in cognitive and functional abilities over time comparing non-demented cognitively “stable” (no change PD normal cognition, PD-NC or PD-MCI), “converters” (decline to PD-MCI or PDD), and “stable PDD.” Assessments included global cognitive tests (MMSE, MoCA), Clinical Dementia Rating scale (CDR) Sum of Boxes (SOB) and Global score), and functional measures (FAQ, PDAQ, PD-Cognitive Functional Rating Scale, ADCS-ADL). Baseline measures were compared using ANOVAs. Repeated measures ANOVA was used for group comparisons over time, with Scheffe for multiple comparisons. 

Baseline cohort included 23 PD-NC, 16 PD-MCI, and 12 PDD (mean disease duration 12y, education 16y), with significant differences in age (p=0.021) and cognitive, functional, and motor scores (p’s<0.0005), but not levodopa equivalents or PD years). Over time, 22 remained non-demented stable, 7 converted, and 6 were stable PDD. There were significant overall effects for global cognitive measures, CDR-SOB, and CDR-Global over time (Hotelling’s trace max F=9.35, CDR-SOB); post-hoc analyses indicated significant differences between non-demented stable and converters vs. stable PDD, but not between non-demented stable and converters. Functional measures showed overall significance for change across time, with significant post-hoc’s between non-demented stable vs. converters and stable PDD, and converters vs. stable PDD.