A real-world study of wearable sensors in Parkinson's disease

Abstract

Most wearable sensor studies in Parkinson's disease have been conducted in the clinic and thus may not be a true representation of everyday symptoms and symptom variation. Our goal was to measure activity, gait, and tremor using wearable sensors inside and outside the clinic. In this observational study, we assessed motor features using wearable sensors developed by MC10, Inc. Participants wore five sensors, one on each limb and on the trunk, during an in-person clinic visit and for two days thereafter. Using the accelerometer data from the sensors, activity states (lying, sitting, standing, walking) were determined and steps per day were also computed by aggregating over 2 s walking intervals. For non-walking periods, tremor durations were identified that had a characteristic frequency between 3 and 10 Hz. We analyzed data from 17 individuals with Parkinson's disease and 17 age-matched controls over an average 45.4 h of sensor wear. Individuals with Parkinson's walked significantly less (median [inter-quartile range]: 4980 [2835-7163] steps/day) than controls (7367 [5106-8928] steps/day; P = 0.04). Tremor was present for 1.6 [0.4-5.9] hours (median [range]) per day in most-affected hands (MDS-UPDRS 3.17a or 3.17b = 1-4) of individuals with Parkinson's, which was significantly higher than the 0.5 [0.3-2.3] hours per day in less-affected hands (MDS-UPDRS 3.17a or 3.17b = 0). These results, which require replication in larger cohorts, advance our understanding of the manifestations of Parkinson's in real-world settings.

Fig. 1. Clock visualization of activity and tremor for a PD and a control participant.

A 24-h clock format visualization for a activity for a participant with PD and b activity for a control participant, c activity, tremor, and medication for a participant with PD, and d activity and (lack of) tremor for a control participant. Data over the duration of sensor wear is depicted in the polar plots, with the brown marker in the innermost and the outermost circle representing the start and end of the sensor wear duration, respectively. The concentric circles each represent different days and the magenta markers (located at 12 AM position) indicate the transition from one calendar day to the next. The activity is classified into one of four classes (lying, sitting, standing, and walking) for each 2-second interval and represented as a corresponding color-coded dot in the polar plot. Each color-coded bar on the polar plots in (c) and (d) jointly represent the rhythmicity index and activity state over a 2-s interval, with the color identifying the activity state and the height of the bar indicating the rhythmicity index (tremor amplitude). The black circle above each radius represents the rhythmicity index threshold, which is set to a value of 3.3. The yellow capsule-shaped markers below each radius represent the medication intake timings for the participants with PD.

Fig. 2. Sensor placement and cloud-based web portal for accessing data.

a A study participant wearing the sensors at five different locations on the trunk and each limb, and b web-portal for accessing the recorded sensor data over the duration of sensor wear. As part of the written consent for participation in the study, the participant shown in (a) provided permission for their image to be used.