The Heartline Experience: Achieving Long-Term Participant Engagement in Digital Health Technology Trials

Background: Digital health technologies can potentially improve clinical research efficiency and increase participant diversity but have challenges with long-term participant engagement. Objectives: The Heartline Study evaluated the impact of a mobile app–based heart health engagement program with the Irregular Rhythm Notification (IRN) and electrocardiogram features of the Apple Watch on diagnosis, treatment, and outcomes of atrial fibrillation in U.S. participants aged ≥65 years. Methods: Participants were randomized 3:1 to the watch group (vs no watch control group), stratified by prevalent atrial fibrillation. Participants interfaced with the study via a custom, app-based engagement program designed to facilitate participant enrollment, post-IRN follow-up, and electronic patient-reported outcome (ePRO) collection. To ensure users would respond to app-based reminders to complete ePROs and follow-up with providers after a potential IRN, targeted engagement strategies based on behavioral science principles were incorporated, including human-centered design, curated health education, and points-based incentives. Results: Of 34,244 enrolled Heartline participants, 32,299 (94%) started the program. High, longitudinal participant engagement was seen, with 93% actively engaged with the app at least weekly after 1 year, and 86% after 2 years. ePRO completion rates were 82% at 1 year and 76% at 2 years. Upon study completion, participants reported high satisfaction with the study and their personal investment. Conclusions: Study adherence in Heartline was high and sustained through 2-year follow-up, using a purposely designed engagement program delivered by a mobile app.