Weekly Variability of an Objective Bradykinesia Score in Parkinson’s Disease—An Observational Longitudinal Study

Background: Parkinson’s Disease is a progressive neurodegenerative disorder characterized by motor and non-motor symptoms. Effective management is critical to improving patient outcomes but is limited by the subjectivity of retrospective assessments of motor symptom burden. The objectives were to describe the weekly variability of objective bradykinesia score (BKS) derived from a wrist-worn device and assess the correlation between BKS variability and the Quality of Life (QoL) of People with Parkinson’s disease (PwP). Method: This observational, longitudinal study is part of the overall self-management project, Empower-PD. The study population consists of 80 PwP. Participants wore a wrist-worn accelerometer watch that measures movement during daily activities to evaluate the degree of bradykinesia as the bradykinesia score (BKS). Weekly median BKSs were collected over a 10-week period. Quality of life was assessed with the PDQ-39 questionnaire at baseline and after 10 weeks. Descriptive statistics assessed BKS variation and distribution. Linear and logistic regression models examined correlations between variability in BKS and QoL. Results: Results showed that 95% of BKS weekly changes were in a range between −4.3 and +4.4 points, with a central tendency near zero. The distribution of BKSs over time indicated that most participants exhibited stable BKSs. No significant correlation was found between BKS changes and QoL at 10 weeks. Conclusions: This study successfully described weekly BKS variations over ten weeks in PwP using objective measurements. The results showed that 95% of all value changes in BKS ranged from −4.3 to 4.4, values which may serve as preliminary distribution-based reference bounds that could inform the design of future studies examining clinically significant changes in BKS.