The macro-economic determinants of health and health inequalities—umbrella review protocol

There has been long-standing recognition of the role of economic factors on health and well-being [1]. These economic factors are consistently identified in local, national and international population health frameworks as both influences on health and levers to improve health and reduce health inequalities. Building on these frameworks, there have been several efforts to quantify the impact of the social determinants relative to other influences such as healthcare services. In line with ongoing advocacy for investment in the wider determinants, the results indicate that social and economic factors are the largest influences on population health [2, 3]. In spite of this evidence and formal calls for action dating back to the Ottawa Charter, there continues to be frustration over the lack of practical policy interventions around social and economic determinants [4].

This lack of action has been attributed to the challenge of understanding the multifaceted impacts of social and economic factors, as well as the need for long-term outlooks to address policy problems [5, 6]. This is particularly pertinent in light of policy debates around Health in All Policies—a move to consider the impact on health and health inequalities in all aspects of government policy [7]. In response, there are calls to consider economic policies as health policies with research and evaluation that would more clearly identify the mechanisms through which economic factors/policies affect health [8]. Berkman notes that ‘understanding the ways in which social and economic policies impact population health is one of the most critical areas for public health today’ [9].

To date, public health researchers have begun to map out the interconnected pathways and linkages between economic conditions/policies and health outcomes. For example, the links between poverty and poor health are wide-ranging and well-documented with lower income being associated with both behavioural risk factors, such as smoking, and a range of negative health outcomes [10, 11]. Similarly, involuntary unemployment and its related income loss are associated with negative health outcomes [12].

More recently, there is growing media and public awareness over income inequalities which have continued to grow amongst OECD (Organization for Economic Co-operation and Development) countries over the last 30 years in spite of significant periods of economic growth [13, 14]. Wilkinson and Pickett have highlighted the body of evidence which shows the impact of income inequalities on a range of population health and social outcomes [15]. Recent research has also highlighted a potential link between ‘neo-liberal’ economic policies such as reductions in public sector spending and increased stress, obesity and health inequalities [16]. These growing income and wealth gaps, combined with environmental concerns, have instigated debate and proposals for alternative economic systems that could deliver improved health outcomes and reduced health inequalities [12, 15, 17].

Seminal social determinants reviews and commissions have begun to specify economic policies within recommendations frameworks. The 2008 World Health Organisation Commission on Social Determinants of Health (SDH) [18] listed a few of these elements, such as ‘social protection’, ‘progressive taxation’, ‘debt relief’ and ‘market responsibility’. This was further developed by the European review of SDH [19], which also looked at ‘gross domestic product (GDP), taxation and welfare’ and ‘economics’. These prominent reports have drawn upon the wide literature of associations between health and, as Dahlgren and Whitehead [20] described it, the general socio-economic, cultural and environmental conditions in society, and also began the process of formalizing these into core themes and categories. The overall pattern is one where purely economic determinants are frequently conceptualized alongside other wider determinants of health (such as environmental and political determinants). This frame might have been too broad, thereby preventing the formation of a comprehensively structured schema of the Economic Determinants of Health. On the other hand, we recognize recent work to define narrower constructs, such as the commercial determinants of health [21]. In our view, these could nonetheless be nested with a wider framework of Economic Determinants of Health, which we hope our review could inform.

The literature has now gone beyond investigating the determinants to identifying potential interventions. Khan et al. carried out a rapid scoping review [22] and found 195 systematic reviews of economic interventions. They found that taxes and subsidies could be used to encourage use of services and healthy patterns of consumption, income transfer programs can support individuals to meet their needs and encourage treatment adherence and that incentives can be used to alter provider and patient behavior. They also found that livelihood support programs can help to increase income, through supporting people to earn a higher income for example. Finally, they found that health-related financial services such as insurance could help householders to manage healthcare-related financial risk. However, we suggest that their definition of economic interventions is limited, ignoring, for example, macro-economic interventions such as fiscal policy and trade policy. Despite progress to date, no comprehensive overview of the macro-economic determinants of health, their relative importance and the different mechanisms through which they affect health has been produced.

We thus aim to carry out a review to provide a rigorous evidence base around the macro-economic determinants of health and health inequalities. We aim to provide a conceptual model to understand the links between the economy and health and use this conceptual model to explore the existing evidence base systematically. We will thus provide evidence to policymakers, researchers and health advocates which can be used to develop evidence-based economic policy interventions and clarify priorities for further research. Given the broad scope of this research question and the large number of existing systematic reviews on each of its subtopics, we aim to carry out an umbrella review—a methodology which involves carrying out a systematic review of reviews [23].

The economy has been defined as a ‘social domain that emphasizes the practices, discourses, and material expressions associated with the production, use and management of resources.’ [8]. The economy is thus conceived of as a complex interacting system which influences health through a number of mediators (access to healthcare, housing, etc.).

The Journal of Economic Literature (JEL) provides a classification [24] of the key concepts that relate to research in economics. Based on the JEL terms and our conceptual framework, we propose that the economic factors that influence health can broadly be conceived of in seven major categories—market regulation; institutions; supply of money; finance and loans; the balance between the public, private and third sector; labour; production and consumption and approaches to the economy. Table 1 presents these seven categories, related subtopics for each category at the local, national and international level as well as illustrative examples of potential health implications. Whilst we acknowledge that this list is not exhaustive, it provides an initial framework to guide our search strategy. We also propose an a priori simplified framework (Fig. 1) to show the broad relationships between economic factors and health that we are investigating.

We used the Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) checklist [33] to develop this umbrella review (see Additional file 1 for the completed checklist).

We developed an ‘economic’ search strategy from the American Journal of Economic Literature (JEL) classification system [24] which is used to categorise economic literature (see Additional file 2 for JEL terms that were included and excluded). We included JEL terms focused on the economy or its key components or policies (see Table 1) and excluded JEL categories that were purely theoretical or methodological, or that were focused on the micro level (individual or household).

We then developed a ‘health outcomes’ search based on key concepts which might be associated with the economic terms we chose, and on a previously used search [36]. In line with this previous umbrella review, we decided not to include specific inequality terms as these might excessively restrict our search results. We modified the Scottish Intercollegiate Guidelines Network (SIGN) terms to limit our search to systematic reviews [44], ensuring the search was more specific than previously used searches [45] for pragmatic reasons.

We refined search terms through consultation with topic experts and information specialists. We further developed the searches through an iterative process, including Medical Subject Headings (MeSH terms) as appropriate [46]. This involved a number of pilot searches followed by a discussion of possible amendments to our strategy at each stage and refinement.

Given the breadth of the review, it was important to balance the sensitivity and specificity of our search strategy. To do this, we identified terms that might have ambiguous health and economic concepts (e.g. deprivation) which would have reduced the specificity. We re-specified or removed them as appropriate to ensure the search remained focused. We developed a pilot search strategy for Medline (see Table 4 for number of results). We tested the sensitivity of the pilot search strategy by checking the inclusion of key ‘tracer papers’—these are papers we would expect our search to find, in line with previous umbrella reviews [35‐37] (see Table 4). All tracer papers were picked up by the pilot search; therefore, the search strategy was finalised for Medline (Additional file 3) and will be adapted for other databases.

This umbrella review will provide, for the first time, a systematic overview of economic determinants of health. It will offer a broad overview of existing evidence and identify key gaps in the current knowledge. We will seek to use the results in a novel conceptual framework which will assist in bringing together the diverse disciplines that inform this field. This can be used to inform international, national and local policy to improve health. Understanding the impact that macro-economic determinants have on health, and gaps in this evidence, will also help set the future research agenda in this field and guide the development of interventions. Building on previous reviews, we will also discuss the impact of context on the economic determinants of health [37] given the increasing recognition of the importance of contextual factors in public health [51].