OBJECTIVE:Emerging evidence links modifiable lifestyle risk factors to disease progression in multiple sclerosis (MS). We sought further evidence around this hypothesis through detailed analysis of the association with disability of lifestyle behaviours of a large international sample of people with MS. MATERIALS AND METHODS:A total of 2469 people with MS from 57 countries provided self-reported data via cross-sectional online survey on lifestyle (mostly with validated tools) and the primary outcome measure, disability (Patient Determined Disease Steps), categorised from 8 steps into 3 categories, mild, moderate and major disability. Multinomial logistic regression modelling derived relative risk ratios (RRRs) for disability categories. RESULTS:RRRs of having moderate vs mild disability were: diet (per 30 points on 100 point scale) 0.72 (95%CI 0.52-0.98), ever smoking 1.32 (1.06-1.65), exercise (moderate/high vs low) 0.35 (0.28-0.44), latitude (per degree from the equator) 1.02 (1.01-1.04), and number of comorbidities (2 vs none) 1.43 (1.04-1.95), (3 vs none) 1.56 (1.13-2.16). RRRs of having major vs mild disability were: exercise (moderate/high vs low) 0.07 (0.04-0.11), alcohol consumption (moderate vs low) 0.45 (0.30-0.68), plant-based omega 3 supplementation 0.39 (0.18-0.86), and disease-modifying medication use 0.45 (0.29-0.70). CONCLUSIONS:Healthier lifestyle has strong associations with disability in our large international sample of people with MS, supporting further investigation into the role of lifestyle risk factors in MS disease progression.