Daily Temporal Associations Between Physical Activity and Symptoms in Multiple Sclerosis.

Background: Symptom severity is negatively associated with physical activity in multiple sclerosis (MS). However, it is unclear how physical activity and symptoms correlate on a day-to-day basis in persons with MS.
Purpose: To determine the temporal within-person associations of pain, fatigue, depressed mood, and perceived cognitive function with physical activity in MS.
Methods: Ambulatory adults with MS (N = 107) completed 7 days of home monitoring. Continuous physical activity data (assessed via wrist-worn accelerometer) and concurrent ecological momentary assessment (5X/day) of pain, fatigue, depressed mood, and perceived cognitive function were collected. Data were analyzed using multilevel mixed modeling.
Results: Fatigue and depressed mood demonstrated bidirectional associations with physical activity, whereas pain and cognitive function did not. Higher than usual fatigue (B = -5.83, p = .001) and depressed mood (B = -4.12, p = .03) were followed by decreased physical activity. In contrast, higher than usual physical activity was associated with subsequent decline in fatigue (B = -0.001, p = .02) and depressed mood (B = -0.0007, p = .02); however, the association between physical activity and fatigue varied across the day.
Conclusions: Physical activity is dynamically related to fatigue and mood on a moment-to-moment basis in MS. Efforts to increase physical activity in MS must incorporate a focus on how symptoms affect and are affected by activity.