Health research needs to focus not just on the growing divide in health status between the world's rich and poor but also on the unacceptable gap between our unprecedented knowledge of diseases (including their control) and the implementation of that knowledge, especially in poor countries. Directed and innovative research is needed to analyse the causes of this situation and to point toward solutions at the global and local levels, both within and outside the health sector—given that inequitable economic globalisation is leading to greater disparities in wealth between and within countries [1].

Because interventions directed at health improvement require, for optimal implementation, infrastructure, equipment, supplies, and competent personnel in adequate numbers, together with intersectoral actions to address the underlying determinants of health, the term “health systems” is increasingly used. Health systems can broadly be described as containing the following principal components: structures, equipment and supplies, policies (technical priorities, financing), people (their numbers, distribution, and skills mix), and processes (how people function within the system and in relation to other sectors). How these components articulate with one another and the communities in which they are based, their effectiveness, and opportunities for modification are also framed by the social and political context in which they have evolved.

This Essay focuses on health systems research (HSR). We begin with an overview of the crisis in health, health systems, and HSR in low-income countries, with a special focus on Africa. Then, we discuss an issue that has come to be termed the “knowledge-implementation gap”, focusing particularly on those types of HSR most concerned with implementation (Box 1). We identify some of the key obstacles to correcting this gap, and conclude with some suggestions for actions that can be taken to increase the quantity and quality of HSR.

Weak Health Systems in Poor Countries

The gap in infant mortality and life expectancy between rich and poor countries is widening substantially. Sub-Saharan Africa is the starkest example of this growing divide. A combination of new and old infectious diseases (in particular HIV infection) and rising rates of injuries have resulted in the populations of countries such as Kenya, South Africa, Zambia, and Zimbabwe losing more than ten years in life expectancy in a short period of time [2]. In many of these countries, this situation is exacerbated by public health services that have been seriously weakened by chronic underfunding and loss of personnel, with an accelerating “brain drain” that is reaching crisis proportions and raising ethical questions regarding recruitment by wealthy countries [3, 4]. Health system dysfunction has been aggravated by ill-considered and inappropriate reforms in the health sector [5]. A stark reflection of these weakened health systems was the stagnation in immunisation rates over the 1990s for the six basic childhood vaccines in many poor countries, despite impressive increases in coverage during the 1980s, the availability of more and improved vaccines, and the subsequent intensive World Health Organization–driven campaigns for the eradication of polio and measles [6].

These challenges will require the implementation of policies that ameliorate the above underlying factors. Research can assist in achieving this but should stress health determinants, population health perspectives, HSR with a focus on implementation, and studies of the effectiveness of strategies designed to bring about equitable social and economic change.

Thus, the Mexico Statement from the Ministerial Summit on Health Research, which took place in Mexico City in November 2004 inter alia, calls on governments to allocate adequate funds to support HSR in order to address priority questions [7].

Implementation Research Has Been Neglected

Health research of the types described above remains only a small fraction of global health research and a tiny proportion of expenditure on health in low-income settings. Recent estimates suggest that only about 0.017% of health expenditure in low- and middle-income countries (around US$134 million) is devoted to such research [8].

In public health research, the focus has traditionally been predominantly on descriptive and analytic epidemiological research (“what”, “why”, “where,” and “who”). There is growing funding for intervention research, particularly for drugs, vaccines, and other products that could benefit the poor through sources such as the Bill and Melinda Gates Foundation ( http://www.gatesfoundation.org/default.htm) and the European and Developing Country Clinical Trials Partnership ( http://www.edctp.org/default.asp?cid=68). However, there is still little funding for, and, therefore, a relative dearth of implementation research (Box 1), particularly in low-income settings (such research addresses the “how” of translating current research knowledge into practice within health and social systems) [9, 10].

Gaps between Knowledge and Action

In developed countries, implementation research focuses particularly on how to promote the uptake of research findings—for example, by evaluating a variety of strategies to enhance the use of clinical guidelines. A recent overview [11] suggests that different approaches might affect different behaviours. For example, reminders may be particularly appropriate for improving preventive behaviours such as immunisation and screening; feedback on performance may be effective for rationalising the ordering of diagnostic tests; and financial interventions may be effective in promoting more rational prescribing.

However, overall these effect sizes are modest, generally resulting in less than 10% improvements in practice. Combinations of a number of interventions appear to be no more effective than single interventions, perhaps because we still do not understand which combinations work best in which circumstances [11]. A recent review suggests that some approaches, such as supportive supervision and audit with feedback, may be effective in low-income settings, but more research is needed—not just on specific approaches to improving the quality of care, but also on the health systems environment that will sustain accessible and high-quality care over time [12].

HSR remains marginalised and has been dominated in the past decade by cost-effectiveness studies that have been promoted by international institutions and incorporated by governments as components of their health sector reform and rationing policies. Such research needs to be complemented by a stronger focus on the development and functioning of health systems, using a combination of quantitative and qualitative methods, including the use of action research that involves practitioners in critical reflections on their own practice. In addition, detailed and comparative case studies of the results of long-term implementation of (especially complex) interventions are needed to identify those programme and contextual factors that lead to success in health development. HSR has the powerful potential to bridge the implementation gap through testing and evaluating activities and systems while simultaneously enhancing the capacity of health staff to evaluate and improve their own performance [13, 14].

However, gaps between knowledge and action persist, with serious consequences for health. For example, full use of existing interventions would cut the more than 10 million annual child deaths that occur globally by more than 60% [15]. A high proportion of the half-million or so maternal deaths that occur globally every year could also be prevented by promoting access to interventions and services of known efficacy [16]. Whilst these problems are seen at their most extreme in low-income countries, they are certainly not restricted to such settings. Studies in Europe and North America show that between 30%–60% of patients do not receive effective treatment for common conditions such as asthma, heart failure, and high blood pressure. [17, 18].

The Scope of Health Systems Research

Since HSR constitutes a relatively new and underdeveloped field, it is important that its scope is defined and the factors inhibiting its development are identified and addressed. A World Health Organization Task Force on HSR recently identified a number of topics for HSR (Box 2) and made recommendations on how such research could be scaled up [19] (more detailed descriptions of each topic and the rationale for addressing them are given in [20]).

Box 3 gives an example of HSR that took place in the impoverished former Transkei “homeland” in South Africa. This example includes aspects of a number of the HSR topics listed in Box 2, such as human resources for health at the district level and below; equitable, effective, and efficient health care; and effective approaches for intersectoral engagement in health.

In some circumstances, health system interventions can be evaluated using randomised trials—particularly cluster trials, where the unit of randomisation may be communities or health facilities. A recent example is a cluster trial of a participatory intervention with women's groups to improve maternal and neonatal mortality in Nepal [21]. Many research questions, however, cannot be addressed by randomised trials—for example, because they may be systemwide in scope. Other approaches need to be considered, such as controlled before-and-after studies and interrupted time-series analyses and process evaluations to better understand how and why interventions work or do not work as intended. Participatory action research, which is a family of research methodologies that pursue action (or change) and research (or understanding) at the same time [22], has the potential to both elucidate constraints to the success of interventions and improve the performance of health staff (Box 3) [23].

Building HSR Capacity

HSR capacity is as yet limited in almost all countries. It is an interdisciplinary endeavour that demands not only technical expertise but also expertise in relating to and working with policymakers and other decision makers in developing research agendas, conducting and interpreting research, and supporting action based on the findings. While training plays an important role in developing research capacity, expertise also has to be built “on the job”, by doing research initially under supervision.

We need larger and more widely applicable research programmes that compare policies and interventions in a range of settings, assess the impact of global factors, and build HSR capacity. These could all be more easily achieved through the development of multi-country collaborative HSR networks.

At a time when substantial sums are being made available for the purchase of efficacious interventions and the development of more effective drugs, vaccines, and other products, it is essential to channel more resources to address the preparedness of health systems for delivering these interventions.

The Next Steps

HSR is becoming recognised as a legitimate and indispensable part of health research. This has been acknowledged in, for example, the recent Mexico Summit statement [7]. But it is imperative to move beyond words. What, therefore, needs to happen—and who should be primarily responsible?

Educational and research institutions need to rapidly build capacity in this area of research, especially within the field of public health, since it is health systems that are the focus. These institutions need to be encouraged to do this by the creation of both financial and nonfinancial incentives. The latter come mainly from publication prestige (which, in some countries, is accompanied by financial reward to the institution or author)—hence, it is urgent that journals, especially those with high impact factors, encourage submission of articles in this area, and (where they meet the required standards) facilitate their expeditious publication. Unlike research leading to the development of pharmaceuticals, vaccines, or other health-related products, HSR has no substantial sponsorship from the private sector. Research bodies and donors can thus play an important role by calling for and funding HSR, and especially implementation research; the derisory amounts currently being spent on HSR need to rapidly increase if the benefits of much existing and new knowledge is to be realised.

Advocacy for HSR in general, and implementation research specifically, also needs to be strengthened. Policymakers can play an important role, both by demanding such research and by ensuring that health-service managers and practitioners see the value of evidence regarding the effectiveness of their activities and even acquire some skills in HSR themselves. The ongoing evaluation of the Integrated Management of Childhood Illness programme offers an indication of the potential benefits of evaluating a major international health programme that aims to promote the uptake of high-quality care based on research evidence [24, 25]. Such evaluations can both demonstrate the positive impacts of such programmes and highlight aspects that require further development if their full benefits are to be achieved, such as low rates of referral among children with severe illness. Presently, civil society organisations and selected research alliances are taking a lead in advocating more research in this area [26]. But until mainstream research organisations actively promote such research, and policymakers demand that the implementation of interventions and programmes is rigorously evaluated, the unconscionable gap between knowledge and its implementation will persist in the health field.