Cardiometabolic diseases (CMDs) are a growing public health concern in Africa. Diabetes prevalence has more than doubled since 1980 on the continent and is projected to double again by 2025.  Cardiovascular disease is the leading cause of death among those over the age of thirty years.  Furthermore, in Southern and East Africa, high prevalence of HIV/AIDS coupled with increasing uptake of antiretroviral therapy adds complexity to risk and morbidity phenotypes for CMD.
A rapid increase in adult obesity is an important factor influencing the spread of CMDs in Africa. Underlying genetic, as well as environmental and behavioural risk factors, contribute to the incidence of obesity. Many studies exploring the association between such risk factors and CMD in Africa to date have been cross-sectional, which prevents us from establishing causal relationships. Longitudinal studies allow us to relate events to specific exposures, facilitating a better understanding of causation.
The wide genetic diversity of African populations – the result of migrations, genetic admixture, natural selection and so on – offers great opportunity for the study of the genomic factors that heighten susceptibility to obesity and, as a consequence, to CMDs. By investigating these factors through longitudinal population-based studies, we can better understand how such diseases are likely to develop in rapidly changing environments, and which populations and individuals are most at risk.
In most regions of Africa, efforts to characterise the continent’s genomic diversity have been limited. A new partnership between the INDEPTH Network of Health and Demographic Surveillance System sites (HDSSs) and the University of the Witwatersrand in South Africa aims to address this deficit.  The Africa Wits-INDEPTH partnership for Genomic Studies (AWI-Gen), funded by the National Institutes of Health, is examining the genomic and environmental influences of body composition and CMDs in Africa through well-characterised cohorts in contrasting contexts.
The INDEPTH Network consists of 47 member HDSS sites in 18 countries across Africa, Asia and Oceania. The sites collect data on over three million individuals. Their trained fieldworkers have extensive experience of conducting demographic and health research in their communities and have developed strong relationships with the participants. The AWI-Gen project has a research platform of over 10,000 individuals aged between 40 and 60 years from five HDSS study sites in Ghana, Burkina Faso, Kenya and South Africa. The study covers west, east and southern Africa, and both urban and rural locations. 
AWI-Gen has blood and urine biomarker data and will soon have genome-wide genotyping data for over 2 million genetic markers, a resource that will be used to compare genomes across the different populations. The initial studies will assess variables related to body composition, aiming to isolate key correlates of body fat mass and distribution and identify risk factors for cardiometabolic outcomes. The banked data and biospecimens will also be made available through Human Heredity and Health in Africa (H3A) repositories or through collaboration with the AWI-Gen team. It is hoped that the project will help to build laboratory infrastructure in participating centres and to strengthen the skills of African researchers in gathering and analysing genomic data.
By studying genomic variation and the interactions between genes and the environment, the AWI-Gen collaboration aims to provide an in-depth picture of genomic diversity in Africa and genetic susceptibility to disease. This will be a vital resource not only for researchers conducting genetic epidemiological studies, but also for health policy-makers as they attempt to develop effective prevention strategies to contain the threat of cardiometabolic diseases.
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3. Ramsay M, et al (2016): H3Africa AWI-Gen Collaborative Centre: a resource to study the interplay between genomic and environmental risk factors for cardiometabolic diseases in four sub-Sharan African countries. Global Health, Epidemiology and Genomics. 1, e20, doi:10.1017/gheg.2016.17
4. Michele Ramsay and Osman Sankoh, as members of the AWI-Gen study and the H3Africa Consortium (2015): African partnerships through the H3Africa Consortium bring a genomic dimension to longitudinal population studies on the continent. International Journal of Epidemiology. 1–4 doi: 10.1093/ije/dyv187