To examine the ability to detect disease progression in multiple sclerosis (MS) with digital mobility outcomes (DMOs).

Current outcome measures hamper our ability to assess people with MS. Wearable devices particularly those measuring real-world mobility, may prove to be a more sensitive measure of disability progression when traditional measures cannot.

602 people with MS with expanded disability status scale score (EDSS) of 3.0-6.5, disability worsening over the previous 2 years and a 30-day freedom from relapses, were recruited across 4 sites in Europe within the Mobilise-D project. Detailed clinical assessments were followed by 7 days of unsupervised walking using a body-worn sensor every 6 months for 2 years. A variety of DMOs were extracted from walking bouts >10s duration from those meeting minimum wear time.

No evidence of progression (NEP) was defined as an absence of a 6-month confirmed progression in EDSS, T25FW or 9HPT. Between-group differences were analysed using Welch’s two-sample t-test or Mann-Whitney U test. A linear mixed-effects model was used to examine longitudinal change. 

Data was available on 556 patients (65% were female), with a mean age 52 years, and a median EDSS score of 5.0 (IQR 2). At 12 months, 26 patients had evidence of progression where measures of walking amount, walking speed and rhythm were significantly different at baseline, before progression became clinically detectable. Similar changes in gait between groups were noted concurrently over the same period.

Despite a lack of clinical change, significant changes in various DMOs of pace occurred during the first 12 months of follow-up across the entire cohort.

Improvements in outcome measures may allow for accurate assessment of neurodegeneration during trials and clinical care. Real-world mobility monitoring can detect changes in people with MS who experience clinical progression longitudinally and may be a measure of subclinical smouldering disease.