No man is an island: disentangling multilevel effects in health services research.

To cite: Ko M, Bindman AB. BMJ Qual Saf 2014;23: 177–179. An extensive literature has established the impact of socioeconomic status on health outcomes. Across a wide range of conditions, poorer individuals face barriers in access to healthcare and suffer worse outcomes of that care. However, individuals do not exist in a vacuum; experiences and behaviours are shaped by the contexts in which people live, work and seek healthcare. Financially disadvantaged patients may have worse outcomes as a result of riskier health behaviours, a higher burden of chronic disease, lower levels of education or other individual characteristics. At the same time, aspects of context such as the quality of the healthcare system can further compound these disadvantages. Poorer patients may receive care from lower quality providers or at overburdened clinics with limited care coordination. Thus, we do not know if poor patients experience lower health status primarily because of individual disadvantages and risks, or if contextual factors also play a large role in adverse outcomes. In this issue of the journal, Lofqvist et al try to disentangle the potential explanations for the worse outcomes experienced by financially disadvantaged patients. The specific aspect of healthcare they explore is avoidable hospitalisations. For common chronic illnesses such as asthma, chronic obstructive pulmonary disease, diabetes, hypertension and heart failure, effective ambulatory care should reduce the frequency of hospitalisation. Using income and hospitalisation data from 43 city districts and municipalities in Stockholm, Sweden, Lofqvist et al found that residence in the lowest income areas was associated with 29% higher odds of avoidable hospitalisation for these and other ambulatory care sensitive conditions. They then examined the extent to which this finding is explained by individual-level versus arealevel characteristics. The authors proposed that low-income patients may have an increased risk of avoidable hospitalisation via a number of pathways including lower baseline health, limited health literacy and poor communication with providers on appropriate care management. The authors also consider that poor individuals tend to reside in poor areas, and the attributes of these areas may contribute to avoidable hospitalisations. They report that, despite a national policy in Sweden to ensure equitable access to healthcare, lowincome areas continue to struggle to recruit high quality providers. Residents are thus disadvantaged by a characteristic of their context, the lower quality of available primary care, and consequently experience a higher rate of avoidable hospitalisations. After adjusting for individual factors, the effect of living in a low-income area remained significant, but reduced to just 5% higher odds of avoidable hospitalisations. Lofqvist and colleagues conclude that, in Sweden, income-related disparities in avoidable hospitalisation are primarily attributable to individual rather than contextual factors.