the UK there are over 450,000 places in care homes catering for older people and those with physical disabilities [1]. A care home can offer personal care and 24 h support (often described as a residential home), with onsite nursing (often described as a nursing home), or a mix of the two. Care home residents have a high prevalence of functional dependency, cognitive impairment, multi-morbidity, frailty, polypharmacy, and behavioural symptoms [2, 3]. These characteristics result in complex healthcare needs. There is currently no national (England) policy or consensus about the best arrangements to meet these needs. Consistently, studies and professional reports have found that residents in care homes have inequitable access to components of health care that would be available to them from the National Health Service (NHS) [4–9] if they lived at home.
In response to such findings, or due to locally perceived problems, a wide variety of local health care delivery models have been developed. These range from the creation of care home specialist teams to the use of incentives and target-based models to change the behaviour of existing care providers. Some of these initiatives have been evaluated, usually in relation to the impact on the specific problem identified locally. Despite their promise, innovative approaches to health care delivery in care homes usually remain highly localised and are often short-lived. Implementing these models at scale and sustaining them beyond initial trial periods has proved difficult [10]. It remains unclear how best to spread successful approaches into routine practice [6, 11].
Interventions that provide health care to care homes do not work in and of themselves; they only have effects through the reasoning and reactions of their recipients [12]. To deal with this degree of complexity requires an appropriate methodology, such as realist review. Realist review is a theory-driven approach, which brings together evidence from multiple sources to make sense of complex interventions as applied in a range of situations and settings. It aims to build plausible and evidence-based explanations for the observed outcomes of complex interventions that have multiple components and involve multiple participants [13]. This realist review seeks to understand more about how key elements of health care provision to care homes work in different contexts.