Impacts of Cognitive Load and Task Initiation Timing on Gait Performance in Parkinson's Disease: A Dual-Task Paradigm...

Gait impairment in Parkinson's disease (PD), especially under dual-task conditions, contributes to falls and reduced quality of life. Although the impact of cognitive load has been explored, the effect of the cognitive task's initiation timing relative to walking is unclear. We investigated how variations in cognitive load and the timing of task initiation affect gait performance in PD patients.

Twelve PD patients and 11 age-matched healthy controls (HCs) completed single-task walking and two arithmetic cognitive tasks (serial-5, serial-7). In dual-task trials, the cognitive task either preceded gait initiation (cognitive-first; C5, C7) or followed it (motor-first; M5, M7). Gait speed, cycle parameters, and inter-limb coordination were measured. Cognitive performance was primarily quantified as the answering speed. This exploratory study analyzed the dual-task data using linear mixed-effects models (LMM).

In PD patients, gait speed was selectively reduced both by higher cognitive load and by initiating the cognitive task before walking (cognitive-first), whereas HCs showed no such effects. Inter-limb coordination of the lower limbs was reduced by higher cognitive load and, in PD patients, by the cognitive-first condition. The cognitive answering speed differed by task load but not by group.

Gait in PD patients is particularly vulnerable when a high-load cognitive task is initiated before walking, suggesting that both the cognitive demand and the timing of task onset modulate dual-task interference. These findings may guide tailored dual-task assessments and rehabilitation strategies for PD.