Abstract

Objective: Caregiving for individuals with traumatic brain injury (TBI) is often highly stressful, and traditional in-person interventions can be inaccessible given the demands of their caregiver role. Mobile health (mHealth) interventions offer a low-burden, scalable alternative by delivering personalized, real- time support. However, the role of app usability in mHealth efficacy remains underexplored in the TBI caregiver population. This study primarily evaluates the relationship between self-reported app usability and the efficacy of a fully automated mHealth intervention, delivered via personalized mobile app messages, in reducing caregiver strain, anxiety, and depression in a TBI caregiver population. The secondary aim is to identify variables that moderate the intervention efficacy among caregivers reporting high app usability.

Methods: We analyzed data from 122 TBI caregivers assigned to receive self-monitoring plus push notifications for self-care as part of a larger randomized controlled trial. App usability was assessed via caregiver responses to a questionnaire item. We applied multivariate linear models with a weighted and centered least squares estimator to assess the moderating effects of app usability and other variables on message efficacy.

Results: Messages were more effective in reducing depression among TBI caregivers who reported high app usability. Moreover, shorter caregiving duration, higher Fitbit step count, and lower prior-week anxiety were significantly associated with improved message efficacy among this high usability group. Conclusions: App usability plays a critical role in the mHealth message efficacy among TBI caregivers. Tailoring interventions based on app usability and identified moderators may optimize health outcomes and support more personalized care for this population.

Keywords: caregiver; traumatic brain injuries; health-related quality of life (HRQOL); mobile health, app usability.