Scaling home designs for healthy cognitive ageing: a realist evaluation perspective

We present an empirically grounded theory of change (ToC) to support delivery at scale of home design for healthy cognitive ageing. Using a realist evaluation lens, we analyse how contexts, mechanisms, and outcomes (CMO) identified in the ‘Designing homes for healthy cognitive ageing’ (DesHCA) research shape scalability. Design principles and features were co-produced with older adults and housing professionals through VR-supported workshops, and in parallel a modified e-Delphi that prioritised outcomes for people and providers. The e-Delphi converged on five cross-cutting outcomes – independence, physical activity, enjoyment, safety, and adaptability – and highlighted system enablers (legislation/regulation, industry and public awareness) and the centrality of ‘value for money’. Workshop CMOs indicated that small, low-cost changes (e.g. contrast, lighting, storage, switch/socket placement) are implementable within existing standards; that flexibility in layouts is critical for diverse and changing needs; and that meaningful engagement between providers and occupants improves adoption. We synthesise these insights into a ToC specifying activities (knowledge, products, procurement levers, curriculum/CPD, local standards), assumptions, and short- and medium-term outcomes that culminate in scaled delivery through both new-build and retrofit. We discuss strengths and limits of the approach and its transferability. The ToC is now guiding an implementation programme in Central Scotland, with early signals of feasibility through cross-sector partnerships and professional demand for practical guidance. • Realist evaluation identifies and offers solutions for scalability challenges. • A theory of change supports scalability of housing for healthy cognitive ageing. • Improved home design can address challenges of cognitive change and dementia. • Professionals need to work with older people to deliver supportive home design. • Scaling supportive home design requires changes for individuals, practice and policy.