Involving People With Dementia in Research: Contributions, Barriers and Evaluation From a Meta‐Synthesis and Qualitative Interview Study

BACKGROUND: Patient and Public Involvement and Engagement (PPIE) can enhance the relevance, acceptability and quality of research; however, its meaningful implementation in dementia research remains insufficiently understood. AIM: (1) To identify methodological procedures for involving people with dementia (PwD) across the research lifecycle, and (2) to explore how members of a dementia PPIE group experience collaboration, contribution, and evaluation of their involvement. METHODS: This mono-method, multi-strand qualitative study combined (1) a meta-synthesis of qualitative primary studies reporting explicit PPIE with PwD and (2) semi-structured interviews with members of a PPIE group. Both strands were analysed using qualitative thematic analysis. Findings were integrated through a crosswalk table and narrative synthesis. RESULTS: The meta-synthesis (33 studies) identified sequential, interrelated methodological conditions for PPIE with PwD across four themes: (1) access and recruitment, through trusted organisations and existing networks; (2) facilitation and support, using adapted communication, flexible pacing, practical aids, and sustained researcher facilitation; (3) forms of involvement, from consultation to co-interviewing, co-analysis, co-authorship, and dissemination; and (4) evaluation of PPIE, which was inconsistently reported and rarely explicit about decision-making impact. Qualitative interviews with 11 PPIE group members generated four experiential themes: (1) group-related aspects (trust, appreciation, PwD representation), (2) structural conditions (organisation, preparation, continuity), (3) communication (clarity, accessibility, feedback), and (4) the handling and impact of contributions. Across strands, findings demonstrated strong convergence: methodological practices identified in the meta-synthesis directly aligned with conditions under which participants experienced involvement as meaningful. Conversely, gaps in reporting and evaluation identified in the literature reflected participants' concerns about limited visibility of impact. CONCLUSIONS: Effective PPIE with PwD requires sustained investment in relationship-building, structured processes, accessible communication and continuous feedback to enable meaningful and inclusive collaboration. By integrating meta-synthesis and experiential data, this study identified psychological safety, relational continuity and the visibility of influence as key in shaping meaningful involvement across research contexts. PATIENT OR PUBLIC CONTRIBUTION: Although people with dementia were not involved as research partners in study conception and design, the study sought to examine and incorporate lived-experience perspectives through the included literature, qualitative interviews and participant validation workshop. This limitation is acknowledged and should be addressed through earlier involvement in future research.