The relationship between physical activity domains by level and illness intrusiveness in people with multiple sclerosis.

Objective: To examine the associations between illness intrusiveness and physical activity level (i.e., time sitting, walking, moderate, and vigorous), and domain-specific physical activity (i.e., work, active transportation, domestic and garden, and recreation), with disability as a mediator, in people with multiple sclerosis (PwMS).

Design: Secondary analysis of cross-sectional study.

Setting: Community-based comprehensive MS Center.

Participants: A total of 183 PwMS with a confirmed MS diagnosis and no recent injuries or relapses in the past 2 months completed a one-time visit. The mean (SD) age was 51.39 (12.15) years, 77% were women, and 90.2% had relapsing MS.

Interventions: Not applicable.

Main outcome measures: Physical activity over the past seven days was measured using the International Physical Activity Questionnaire-Long Form (IPAQ-LF), illness intrusiveness was measured using the Illness Intrusiveness Rating Scale (IIRS), and disability was measured using the Patient Determined Disease Steps (PDDS). Individual mediation models were run for each physical activity level, with illness intrusiveness (dependent variable), disability (mediator), and covariates (age, race, gender, disease duration, and high fatigue). Exploratory domain-specific models were then examined.

Results: Greater overall vigorous physical activity, specifically recreational, and walking at work were directly associated with lower illness intrusiveness. Increased overall walking, specifically for recreation, as well as overall moderate physical activity, contributed to decreased illness intrusiveness through their effects on disability. More time spent sitting was also indirectly related to higher illness intrusiveness through disability.

Conclusions: The findings further elucidate the connections between physical activity and illness intrusiveness, which may help inform future interventional approaches.