Intervention Mediators in a Randomized Controlled Trial to Increase Physical Activity and Fatigue Self-management Behaviors Among Adults With Multiple Sclerosis
Abstract Background People with multiple sclerosis (MS) often experience fatigue, which is aggravated by inactivity. Identifying mediators of changes in physical activity (PA) and fatigue self-management (FSM) behaviors could optimize future interventions that reduce the impact of MS fatigue. Purpose To examine the effects of telephone-delivered interventions on Social Cognitive Theory constructs and test whether these constructs mediated secondary outcomes of PA and FSM behaviors. Methods Participants with MS (n = 208; Mean age = 52.1; Female = 84.6%) were randomized into contact–control intervention (CC), PA-only intervention, and PA+FSM intervention. Step count (Actigraphy) and FSM behaviors as well as self-efficacy, outcome expectations, and goal setting for PA and FSM were measured at baseline, post-test (12 weeks), and follow-up (24 weeks). Path analyses using bias-corrected bootstrapped 95% confidence intervals (CI) determined whether constructs at post-test mediated behaviors at follow-up when adjusting for baseline measures. Results Path analysis indicated that PA-only (β = 0.50, p < .001) and PA+FSM interventions (β = 0.42, p < .010) had an effect on goal setting for PA, and that PA + FSM intervention had an effect on self-efficacy for FSM (β = 0.48, p = .011) and outcome expectations for FSM (β = 0.42, p = .029). Goal setting for PA at post-test mediated the effects of PA-only (β = 159.45, CI = 5.399, 371.996) and PA + FSM interventions (β = 133.17, CI = 3.104, 355.349) on step count at follow-up. Outcome expectations for FSM at post-test mediated the effects of PA + FSM intervention on FSM behaviors at follow-up (β = 0.02, CI = 0.001, 0.058). Conclusions Goal setting for PA and outcome expectations for FSM may be important constructs to target in telephone-delivered interventions designed to reduce the impact of MS fatigue. Trial registration Clinicaltrials.gov (NCT01572714)