Research on health transition in Africa: time for action

An increasing burden of disease in Africa arises not only from communicable diseases and NCDs but also from the interactions between them, e.g. between tuberculosis and malnutrition, human papilloma virus and cervical cancer, and hepatitis B virus and hepatoma. The burden of chronic NCDs (including for example diabetes) is likely to be further uncovered as scaled-up programmes of antiretroviral treatment (ART) of HIV-infected people lead to reduced HIV/AIDS mortality but increased morbidity related to chronic HIV infection and ART [12]. Increasing numbers of people in Africa are therefore at risk of possible metabolic side-effects resulting from life-long ART, but there is little knowledge of their epidemiology [13, 14] or of how health systems can most effectively address them. Research on health transition in Africa needs to include research on the interactions between communicable diseases and NCDs: the biology of their interaction, their clinical course and distribution, and the delivery of interventions aimed at their prevention and treatment.

Planning an improved health system response to health transition, with a priority for primary health care [15], requires assessment of the population burden not only of communicable diseases but also of NCDs and associated risk factors [16]. For example, the WHO STEPwise approach to surveillance of NCD risk factors uses a standard survey instrument and a methodology that can be adapted in different settings [17]. A lack of high quality health information is one of the major obstacles in developing appropriate preventative strategies for NCDs at the national level [18]. The need for good quality comparable data on disease burden and risk, to aid planning and implementation of prevention and control strategies for NCDs, is greatest among low- and middle-income countries [19]. There is an enormous gap between the sparse population-based data so far available on chronic NCDs and the comprehensive data needed for a good understanding of their distribution in Africa. Baseline data are needed, for example, on the prevalence of diabetes, hypertension and obesity as well as related cardiovascular disease risk factors in both rural and urban settings.

Prospective cohort studies are important in epidemiological research on health transition. They have made enormous contributions, for example, to our understanding of the dynamics and impact of the HIV epidemic [20]. In populations in developed countries, prospective cohort studies have proved crucial in understanding the aetiology, course and outcome of NCDs in have informed the design of prevention programmes, and are a valued long-term investment in public health. In Africa prospective cohort studies on NCDs and their risk factors can contribute to a better understanding of NCD aetiology, course and outcome [21]. In addition to the use of cohort studies to investigate a range of NCDs and their risk factors over the course of an individual's lifetime, long-term follow-up would also enable investigation of inter-generational health effects, e.g. the relationships between maternal health and nutrition status, intrauterine growth and susceptibility to cardiovascular and metabolic diseases. Although NCDs cause a large and growing disease burden in sub-Saharan Africa, there are very few prospective cohort studies on NCDs in developing countries in the region: the Birth to Twenty Cohort in Johannesburg-Soweto (South Africa), the Heart of Soweto Study on cardiovascular disease, and the Women's Health Study in Accra (Ghana) [22]. In meeting the urgent need for longitudinal cohort studies on NCDs in Africa, well established population-based study sites are ideal, since they offer cost savings [21]. The population-based cohort study in rural Masaka District in Uganda is a good example of how a population-based study site, in this case initially established for HIV epidemiology research, can be successfully used as a platform for research on health transition by expanded the research scope to include chronic NCD epidemiology [22].

Although research in Africa has made a substantial contribution to progress in improving the delivery of effective interventions against communicable diseases such as HIV, tuberculosis and malaria, research on NCDs has lagged behind that on communicable diseases. An effective response to health transition requires research on delivering effective interventions for NCDs as well as for communicable diseases. Cost-effective interventions for chronic NCDs are available [23] and successful primary care approaches to NCD care in developing countries have been developed (e.g. a model in rural South Africa) [24]. As the health service entry point for the vast majority of people, primary care is the key element in the health system response to health transition, playing a pivotal role in the delivery of prevention and care interventions for communicable diseases and NCDs [15]. In place of the current approach to primary care of people with chronic NCDs, which is often unstructured and inadequate, a programmatic public health framework for NCDs has been proposed [25] which builds on the experience of standardized diagnostic and management protocols and information management systems for HIV and tuberculosis interventions [26]. The response to health transition may be improved through the development of primary care services that cut across conventional categories of communicable diseases and NCDs. Health system research is needed on the effectiveness of these proposals for an improved response to health transition and on scaling-up effective approaches in large-scale delivery programmes [15].

Research on health intervention delivery programmes complements the more upstream, policy-oriented research priorities identified through a "grand challenge" exercise [27]. Evaluation of the relevance and effectiveness of these global policy research priorities is necessary in different settings, including in Africa as part of the overall research agenda for health transition.