Abstract

Background: Caregivers of persons with chronic illnesses often face negative stress-related health outcomes and are unavailable for traditional face-to-face interventions due to the intensity and constraints of their caregiver role. Just-in-time adaptive interventions (JITAIs) have emerged as a design framework that is particularly suited for interventional mobile health studies that deliver in-the-moment prompts that aim to promote healthy behavioral and psychological changes while minimizing user burden and expense. While JITAIs have the potential to improve caregivers’ health-related quality of life (HRQOL), their effectiveness for caregivers remains poorly understood.

Objectives: The primary objective of this study is to evaluate dose-response relationship of a fully automated JITAI-based self-management intervention involving personalized mobile app notifications targeted at decreasing the level of caregiver strain, anxiety, and depression. The secondary objective is to investigate whether the effectiveness of this mobile health intervention was moderated by caregiver group. We also explored whether the effectiveness of this intervention was moderated by 1) previous HRQOL measures; 2) number of weeks in study; 3) step count; and 4) minutes of sleep.

Methods: We examined 36 caregivers from 3 disease groups (10 from spinal cord injury, 11 from Huntington disease, and 25 from allogeneic hematopoietic cell transplantation) in the intervention arm of a larger RCT (subjects in the other arm received no prompts from the mobile app) designed to examine the acceptability and feasibility of this intensive type of trial design. A series of multivariate linear models, implementing a weighted and centered least-squares estimator, were used to assess the JITAI efficacy and effect.

Results: We found preliminary support for a positive dose-response relationship between the number of administered JITAI messages and JITAI efficacy on improving caregiver strain, anxiety and depression; while most of these associations did not meet conventional levels of significance, there was a significant association between high frequency JITAI and caregiver strain. Specifically, administering 5-6 messages per week, as opposed to no messages, resulted in a significant decrease in the HRQOL score of caregiver strain with an estimate of -6.31 (95% CI: -11.76, -0.12, P = .046). In addition, we found that the caregiver groups and the participants previous weeks’ level of depression moderates JITAI efficacy.

Conclusions: This study provide preliminary evidence to support the effectiveness of the self-management JITAI and offer practical guidance for designing future personalized JITAI strategies for diverse caregiver groups.

Trial Registration: ClinicalTrial.gov NCT04556591

Key words: Caregiver, Just-in-time adaptive intervention (JITAI), Mobile health intervention, health-related quality of life (HRQOL)