Dual-task performance during the Timed Up and Go test in Parkinson's disease - the impact of freezing and cognition

Background: Dual-task interference (DTI) on gait is well documented in Parkinson's disease (PD), but how dualtasks affect functional mobility is less known. Understanding how cognition and freezing of gait (FOG) further impact dual-task ability is important for risk assessment and subsequent delivery of targeted rehabilitation. Research question: What is the DTI on completion time of the Timed Up and Go, and DTI on response rate of a serial subtraction task when performed simultaneously, and is DTI impacted by FOG or cognition? Methods: A cross-sectional study design was used. Demographic and clinical characteristics of participants were collected, including global cognition and self-reported FOG. The TUG test was performed with and without a serial subtraction task. Completion times on TUG and response rates on the serial subtraction task was compared between single and dual-task performance using paired samples t-test or Wilcoxon signed rank test as appropriate. Prioritization between tasks was compared with one-sample Wilcoxon signed rank test. The impact of FOG and cognition was investigated with multiple linear regression, controlling for age, sex, and disease severity. Results: A total of 77 people with mild to moderate PD were included. Significant DTI was observed for both the gait (TUG) and cognitive (response rate) tasks. No statistically significant pattern of prioritization was observed between motor and cognitive tasks. Global cognition was significantly related to both completion time and response rate in single and dual-tasking, whereas FOG was not found to be associated to the outcomes in either condition. Significance: Cognition appears to significantly relate to performance of functional mobility in single and dualtask conditions, which should be considered during routine mobility assessments in people with PD.