Disease progression in Parkinson’s disease patients with mild cognitive impairment: 5-year longitudinal study from the early Parkinson’s disease longitudinal Singapore (PALS) cohort

Aim: To investigate motor, non-motor and cognitive progression in early Parkinson’s disease (PD) patients with Mild Cognitive Impairment (MCI).

Methods: PD patients were recruited within 1 year of diagnosis and were classified into PD-MCI group and PD with normal cognition (PD-NC) group. H&Y staging scale, MDS-UPDRS part III were used to assess disease severity and motor progression. Non-motor symptom scale (NMSS) was used to evaluate the NMS progression. Cognitive progression was assessed from 5 cognitive domains. Annual progression changes in the longitudinal outcomes were examined via linear mixed model with random intercept effect. False discovery rate (FDR) method was performed to control for multiple testing comparison and q-value was calculated. We set the threshold of q-values as 0.1.

Result: A total of 205 PD patients, including 107 PD-MCI and 98 PD-NC patients were assessed prospectively over a 5-year period. PD-MCI patients, compared to PD-NC group, had a significantly higher progression rate in H&Y score (0.11 vs. 0.06, p=0.03, q=0.08), MDS-UPDRS motor score (3.11 vs. 1.90 p<0.001, q=0.06) and postural instability gait difficulty (PIGD) score (0.40 vs. 0.20, p=0.02, q=0.07). PD-MCI group also exhibited significantly faster deterioration in NMSS perceptual domain (PD-MCI vs. PD-NC: 0.38 vs. -0.04, p=0.01, q=0.06) and cognitive visuospatial domain (PD-MCI vs. PD-NC: 0.13 vs. -0.06, p=0.048, q=0.09) after adjustment for confounders and multiple comparisons.

Conclusions: PD-MCI patients had faster decline in motor functions, visuo-perceptual and visuospatial performance. These findings provide a more comprehensive prognosis of PD-MCI, which could be helpful for clinician to manage PD-MCI patients.