A co-designed gamified mHealth platform for adolescents and young adults with intellectual and developmental disabilities: System architecture and mixed-methods proof-of-concept

Adolescents and young adults with intellectual and developmental disabilities (IDs) experience disproportionately low physical activity and high sedentary time yet remain insufficiently served by scalable and cognitively accessible health-enhancing physical activity (HEPA) programmes. This study reports proof-of-concept evidence for IDHEApp, a co-designed, gamified mobile health (mHealth) intervention integrated with a wearable activity tracker to promote physical activity in cognitively diverse users. We conducted an 8-week, convergent mixed-methods pilot randomised controlled trial across two European community IDs services (Rome, Italy; Rijeka, Croatia). Sixty adolescents and young adults were randomised (1:1) to an intervention arm (IDHEApp with Fitbit-enabled feedback and gamified step challenges) or a control arm (Fitbit monitoring plus usual routines). Quantitative outcomes were derived from wearable data (primary: daily step count; secondary: activity intensity and posture-related indicators) and analysed as exploratory behavioural signals using ANCOVA adjusted for baseline values. Qualitative data were obtained through two-phase focus groups (pre-implementation formative assessment and post-implementation technology exposure) with adolescents and young adults and caregivers and examined using reflexive thematic analysis. The intervention was technically feasible to deploy in real-world service settings at both sites. The strongest between-group signal was observed for daily steps (+2068 steps/day; p < 0.001), whereas activity-intensity and posture metrics demonstrated smaller and less consistent patterns. Thematic findings suggested that simple, non-competitive gamification (step goals, points, badges) was readily understood and perceived as motivating, supporting sustained engagement; however, technical barriers (Bluetooth pairing, synchronisation, device charging) increased reliance on caregiver support. Collectively, these findings indicate that IDHEApp is a promising mobile–wearable ecosystem to support HEPA in adolescents and young adults with IDs and justify further optimisation to enhance technical robustness, reduce caregiver burden, and evaluate effectiveness over longer follow-up periods.