Reallocation of time between device-measured 24-hour movement behaviours and risk of multiple sclerosis

Background: Multiple sclerosis (MS) is an immune-mediated neuroinflammatory disease with an early-onset. Previous studies on the relationship between physical activity (PA) and MS provided inconsistent results. However, no study used objective measures of PA, and little is known about the association with other movement behaviours such as sedentary time.
Purpose: The objective of the study was to examine the theoretical association of reallocation of time between device-measured movement behaviours with MS risk.
Methods: This study used data from the UK Biobank cohort, and included 96,253 participants followed between 2013-2022. Incident MS cases were ascertained based on self-report, primary care, hospital inpatient data and death data. Movement behaviour was measured with an Axivity AX3 wrist-worn triaxial accelerometer. Machine-learning models were used on accelerometer data to classify the movement behaviours (sleep, sedentary behaviour, light PA and moderate-to-vigorous PA [MVPA]). Cox proportional hazards models with age as the timescale and adjusted for confounders were used to investigate how reallocating time between movement behaviours composition, modelled using isometric log-ratio pivot coordinates, was associated with MS risk.
Results: Reallocating 20 minute/day to MVPA from all other behaviours proportionally was associated with a 12% lower risk of MS (HR=0.88, 95%CI=0.81-0.95). Additionally, reallocating 20 min from any behaviour to MVPA was associated with a lower MS risk. Conversely, reallocating 20 minutes from MVPA to any other behaviour, was associated with an higher MS risk.
Conclusions: Our findings showed that reallocating time to MVPA was associated with a reduced MS risk. These results are important for planning MS prevention programs and warrant further studies to understand which type and level of PA are the most beneficial.
Practical implications: Our study provide prospective evidence in favour of the health benefits of PA and suggest that increasing time spent in MVPA would be beneficial in MS prevention.
Funding: LIH funding