Treatment fidelity and adherence in a pilot physical activity randomized controlled trial for people newly diagnosed with multiple sclerosis.

BACKGROUND: Understanding treatment fidelity, particularly adherence to treatment, is critical in early-stage clinical trials of physical activity (PA) behavioral interventions. PURPOSE: This secondary data analysis examined adherence to a 16-week, remotely-delivered COM-B-based behavioral intervention and explored associations with changes in PA outcomes and baseline characteristics among people newly diagnosed with multiple sclerosis (PNDwMS). METHODS: PNDwMS (N = 50) were randomized to either the PA intervention or waitlist condition. The analysis focused on adherence rates with intervention components, including coaching, newsletters, self-monitoring step counts using logbook and PA tracker, and overall adherence among participants who received the intervention (n = 24). Spearman correlations estimated the associations between adherence and changes in PA outcomes. Spearman and point biserial correlations identified potential correlates of adherence based on baseline demographics, clinical characteristics, and MS outcomes. RESULTS: The overall adherence rate with intervention components was 95.2%. The mean adherence rates for coaching, newsletters, logbook, and PA tracker were 99%, 88%, 96%, and 95%, respectively. Adherence with coaching sessions was moderately associated with changes in self-report PA (International Physical Activity Questionnaire) (|r| ∼ 0.35 - 0.37). The primary correlates of adherence were sex, race, baseline MVPA, fatigue, and physical health-related quality of life (HRQoL). CONCLUSIONS: Our results highlight that adherence to coaching is associated with changes in self-report PA. We further highlight biological sex, race, PA level, fatigue, and physical HRQoL as correlates of adherence. Those results should be considered for optimizing treatment fidelity in future trials of PA behavioral interventions for PNDwMS.