Examine the construct validity and acceptance of digital mobility outcomes (DMOs) in the largest study of unsupervised walking in people with neurological disease, Mobilise-D.

There is a rapidly growing number of digital health outcome measures. The unsupervised measurement of real-world mobility produces DMOs that represent a patient's gait and walking behaviour, which are not limited to typically used measures, such as step count. 

600 people with Parkinson’s disease (PD) and 602 with multiple sclerosis (MS) were recruited across Europe. Clinical assessments were followed by 7 days of unsupervised mobility monitoring using a body-worn sensor. Valid data was considered as ≥3 days with ≥12 hours wear time per day. A variety of DMOs were extracted from walking bouts >10s duration, and segmented by walking bout duration. Construct validity was assessed by testing correlations based on an a priori hypothesis.

531 PD (mean age 66 years, 64% male, mean Movement Disorder Society-Unified Parkinson’s Disease Rating Scale total score of 48) and 556 MS (mean age 52 years, 65% female, median expanded disability status scale score of 5) participants had a valid assessment. Construct validity was met for 12 and 21 of 24 DMOs in PD and MS, respectively. Irrespective of disease, DMOs worsen as disease severity states increases. The most consistent results were seen in DMOs reflecting the amount and pace of walking.

Acceptance to being monitored was similar in both groups with ≥92% accepting of being remotely monitored during the study and ≥79% willing to wear the device as part of clinical care.

Real-world mobility monitoring is a comprehensive method of gait assessment and a valid construct in people with MS and PD. Patients are ready and accepting of its potential use. Further analysis will help to establish the place of DMOs in future clinical care and trials.