Diet and physical activity in multiple sclerosis: associations with quality of life and disability by disease duration

Background Healthy lifestyle factors are associated with higher quality of life (QoL) and reduced disability in people with multiple sclerosis (pwMS). Whether these associations differ according to MS duration is unclear. We examined associations between diet, supplement use, wellness activities, and physical activity with QoL and ambulatory disability, and whether these associations differed between pwMS diagnosed within ≤ 5 years versus > 5 years. Methods Cross-sectional self-reported survey data from 1,083 pwMS were analysed. Diet, supplement use, and wellness activities were queried via tick-box options and recategorised. Physical activity was assessed using the Godin–Shephard Leisure-Time Physical Activity Questionnaire. QoL was measured using Neuro-QoL, and ambulatory disability using the Patient Determined Disease Steps. Multivariable linear and moderation analyses were conducted. Results Associations differed by MS duration: a low-saturated fat diet and “other” diets were associated with lower QoL in the > 5-years group, whereas omega-3 supplement use was associated with higher physical QoL in the ≤ 5-years group. Physical activity was associated with higher QoL in both groups, with mostly stronger associations within ≤ 5-years. Very active physical activity was associated with lower ambulatory disability across both groups. Mind-based wellness activities were associated with lower QoL in the > 5-years group, with no group differences. Vitamin D supplement use was not associated with outcomes. Conclusions Physical activity is associated with higher QoL and lower disability irrespective of MS duration and should be integrated across the disease course. MS duration may modify associations between other lifestyle factors and QoL, supporting consideration of disease stage when tailoring lifestyle recommendations.