Peer-reviewed article

Moderators of design and delivery component effects on engagement with a digital parenting intervention: evidence from a factorial randomized trial in Tanzania.

Roselinde Janowski, Yulia Shenderovich, Joyce Wamoyi, David Stern, Jamie M Lachman et al. · 7 Jan 2026

Abstract

BACKGROUND: Digital health interventions are rapidly expanding in low- and middle-income countries (LMICs), yet little is known about how design and delivery components can be tailored to support engagement across diverse populations. Addressing this gap is critical for effective and equitable implementation. PURPOSE: This study used a factorial experiment, embedded within the Optimization Phase of the Multiphase Optimization Strategy (MOST), to examine whether caregiver characteristics moderated the effects of design and delivery components on engagement with an app-based parenting intervention in Tanzania. METHODS: A 2 × 2 × 2 cluster-randomized factorial experiment was conducted in Mwanza, Tanzania (16 clusters; 614 caregivers of adolescents). Three components were tested: guidance (guided vs self-guided), app design (unstructured vs structured), and digital support (enhanced vs basic). Engagement was operationalized as the number of intervention modules completed, which was tracked automatically via the app. Generalized linear mixed-effects models examined moderation by caregiver gender, age, financial stress, food insecurity, positive parenting, child maltreatment, and caregiver depression. RESULTS: Gender, age, positive parenting, and depressive symptoms moderated the effects of specific components on engagement. Women showed significantly higher engagement with the unstructured versus structured app design (incidence rate ratio [IRR] = 1.48, 95% CI, 1.23-1.80), whereas no significant app design differences were observed among men. Older caregivers showed greater engagement under guided delivery (vs self-guided; IRR = 1.15, 95% CI, 1.06-1.25) and enhanced digital support (vs basic support; IRR = 1.15, 95% CI, 1.06-1.26). Greater engagement under guided versus self-guided delivery was also observed among caregivers reporting more positive parenting practices (IRR = 1.03, 95% CI, 1.02-1.04) and higher depressive symptoms (IRR = 1.06, 95% CI, 1.03-1.09). However, caregivers reporting more positive parenting practices showed lower engagement under enhanced digital support (vs basic support; IRR = 0.96, 95% CI, 0.95-0.98). No moderation effects were observed for financial stress, food insecurity, or child maltreatment. CONCLUSIONS: Tailoring design and delivery components to specific caregiver characteristics may enhance engagement and promote more equitable implementation of digital parenting interventions in LMICs. CLINICAL TRIAL REGISTRATION NUMBER: The trial was pre-registered on the Pan-African Clinical Trial Registry PACTR202210657553944; https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=24051.