ENHANCE (Tailored Intervention for Brain Health and Cognitive Enrichment for Cognitive Health), a Coach-Supported Digital Intervention for Dementia Prevention in Underserved Older Adults: Co-Design and Usability Study (Preprint)

BACKGROUND Digital multidomain interventions hold promise for dementia risk reduction; however, populations at higher dementia risk, including those experiencing socioeconomic and educational disadvantage, remain underrepresented in trials, and engagement with digital interventions often declines over time. Coproduction and blended models that combine digital tools with human support may improve reach, acceptability, usability, and sustained engagement. Designing interventions that are usable and acceptable for individuals facing structural, educational, or digital barriers (underserved groups) is therefore likely to produce solutions that are both accessible and scalable for the wider midlife and older adult population. OBJECTIVE This study aims to describe the coproduction process used to develop ENHANCE (Tailored Intervention for Brain Health and Cognitive Enrichment)—a coach-supported digital intervention targeting 10 modifiable dementia risk factors in older adults from underserved groups—and report key outputs and lessons learned for equitable digital prevention design. METHODS We coproduced ENHANCE between July 2023 and February 2025 using a multistage development process guided by the Medical Research Council framework for complex interventions and the Double Diamond design model. The person-based approach informed user-centered guiding principles (key design objectives), while behavior change content was operationalized using behavioral change theories. Coproduction followed 4 phases. The Discovery phase explored barriers to engagement with existing digital materials and identified candidate components for each dementia risk-factor module. The Define phase translated these insights into guiding principles and blueprints of each risk-factor module integrated with behavioral change components. The Design phase involved iterative co-production and usability testing of prototypes. The Delivery phase evaluated a high-fidelity prototype through a 1-week usability study with coaching support. Contributors included 162 research participants recruited from underserved community settings, 33 patient and public involvement contributors, and 4 human–computer interaction experts. Throughout development, coproduction focused on reducing literacy, digital confidence, and cultural barriers to maximize usability across diverse adult populations. RESULTS Coproduction produced (1) evidence-informed module strategies for targeted dementia risk factors; (2) a set of guiding principles to ensure low-literacy, culturally relevant, and accessible content, supporting both equity of access and wider population usability; (3) a meadow-themed app integrating tailored check-ins, educational videos, cognitive training games, and in-app messaging; and (4) a structured coaching model, including onboarding, brief follow-up, and accompanying coaching manuals. Iterative testing and refinement improved navigation, simplified language, reduced text burden, and ensured the use of familiar and accessible game formats, resulting in a feasibility-ready prototype. CONCLUSIONS ENHANCE is a coproduced, coach-supported digital intervention designed to be accessible for underserved midlife and older adults at increased dementia risk, with design features to support accessibility, engagement, and scalability across the wider aging population. The development process illustrates how integrating coproduction with behavioral science and usability methods can support principled intervention design for equitable digital dementia prevention.