Longitudinal study of changes in walking and cognition by motor subtype of Parkinson's disease

Postural instability and gait dysfunction (PIGD) subtype of PD has been associated with a more rapid progression of cognitive and motor dysfunction while tremor dominant (TD) subtype is associated with more severe tremors and slower disease progression. The purpose of this study was to examine longitudinal differences in walking and cognition in pwPD between subtypes.

This was a five-year observational longitudinal study. Participants underwent motor and non-motor assessments every six months.TD and PIGD clinical subtypes were determined at the initial visit. Primary outcomes were gait speed, double support time, turning velocity, Timed up and Go Cognitive (TUGc) duration, and MoCA.

Forty people living with PD were included in this study [TD (n = 24), PIGD (n = 16)]. PIGD subtype had longer disease duration (p = 0.018) than the TD subtype and worse overall disease severity with higher scores on the Movement Disorders Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part 2 (p = 0.001), Part 3 (p = 0.026), and total score (p = 0.003) at baseline. Gait speed showed similar rates of change between the TD and PIGD subtypes, with no significant subtype-by-time interactions. Double support time and TUG cognitive duration changed significantly over time across both subtypes, while turning velocity did not; for all outcomes the rate of change did not differ between the TD and PIGD subtypes. Cognition did not significantly decrease across time.

While baseline differences between TD and PIGD groups were evident, the similar rates of change over time suggest that subtype identification alone may not be sufficient for predicting individual trajectories.