How did New Zealand's regional District Health Board groupings work to improve service integration and health outcomes: a realist evaluation.

Objectives: In Aotearoa New Zealand (NZ), integration across the healthcare continuum has been a key approach to strengthening the health system and improving health outcomes. A key example has been four regional District Health Board (DHB) groupings, which, from 2011 to 2022, required the country's 20 DHBs to work together regionally. This research explores how this initiative functioned, examining how, for whom and in what circumstances regional DHB groupings worked to deliver improvements in system integration and health outcomes and equity.

Design: We used a realist-informed evaluation study design. We used documentary analysis to develop programme logic models to describe the context, structure, capabilities, implementation activities and impact of each of the four regional groupings and then conducted interviews with stakeholders. We developed a generalised context-mechanisms-outcomes model, identifying key commonalities explaining how regional work 'worked' across NZ while noting important regional differences.

Setting: NZ's four regional DHB groupings.

Participants: Forty-nine stakeholders from across the four regional groupings. These included regional DHB governance groups and coordinating regional agencies, DHB senior leadership, Māori and Pasifika leadership and lead clinicians for regional work streams.

Results: Regional DHB working was layered on top of an already complex DHB environment. Organisational heterogeneity and tensions between local and regional priorities were key contextual factors. In response, regional DHB groupings leveraged a combination of 'hard' policy and planning processes, as well as 'soft', relationship-based mechanisms, aiming to improve system integration, population health outcomes and health equity.

Conclusion: The complexity of DHB regional working meant that success hinged on building relationships, leadership and trust, alongside robust planning and process mechanisms. As NZ reorients its health system towards a more centralised model underpinned by collaborations between local providers, our findings point to a need to align policy expectations and foster environments that support connection and collegiality across the health system.