Physical activity monitoring to assess disability progression in multiple sclerosis

Background Clinical outcome measurement in multiple sclerosis (MS) usually requires a physical visit. Remote activity monitoring (RAM) using wearable technology provides a rational alternative, especially desirable when distance is involved or in a pandemic setting. Objective To validate RAM in progressive MS using (1) traditional psychometric methods (2) brain atrophy. Methods 56 people with progressive MS participated in a longitudinal study over 2.5years. An arm-worn RAM device measured activity over six days, every six months, and incorporated triaxial accelerometry and transcutaneous physiological variable measurement. Five RAM variables were assessed: physical activity duration, step count, active energy expenditure, metabolic equivalents and a composite RAM score incorporating all four variables. Other assessments every six months included EDSS, MSFC, MSIS-29, Chalder Fatigue Scale and Beck's Depression Inventory. Annualized brain atrophy was measured using SIENA. Results RAM was tolerated well by people with MS; the device was worn 99.4% of the time. RAM had good convergent and divergent validity and was responsive, especially with respect to step count. Measurement of physical activity over one day was as responsive as six days. The composite RAM score positively correlated with brain volume loss. Conclusion Remote activity monitoring is a valid and acceptable outcome measure in MS.