A Comparison of Activity Monitor Data from Devices Worn on the Wrist and the Waist in People with Parkinson's Disease

Abstract

Background: It is unclear if it is appropriate for people with Parkinson's disease (PD) to wear activity monitors on the wrist because of the potential influence of impairments on the data. Objective: The objective of this study was to determine (1) whether activity monitor data collected from devices worn at the wrist and waist are comparable and (2) the contribution of PD impairments to any differences in step and activity counts at the wrist and waist. Methods: A total of 46 community-dwelling people with PD wore an accelerometer at the wrist and waist simultaneously for 1 week. Motor impairments (rigidity, bradykinesia, tremor, dyskinesia) were assessed using the Movement Disorders Society Unified Parkinson's Disease Rating Scale part III (motor examination) and part IV (motor complications). Results: Higher values were recorded by the wrist monitor for steps/day (wrist, 9236 [standard deviation (SD) 3812]; waist, 5324 [SD 2800]; difference 3912; P < 0.001) and activity counts/day (wrist, 872,590 [SD 349,148]; waist, 186,491 [SD 101,989]; difference 686,099; P < 0.001). However, the wrist and waist values were strongly correlated (steps, r = 0.89; counts, r = 0.74; P ≤ 0.001). Increased tremor and dyskinesia explained 19% of the variation in the difference in average steps/day, and these variables plus reduced bradykinesia explained 24% of the variation in the difference in average activity counts/day. Conclusion: Wrist monitors are likely to overestimate activity, particularly in people with tremor and dyskinesia. Nonetheless, activity monitors can be worn on the wrist if the aim is to monitor change rather than accurately record activity.