Genomic and environmental risk factors for cardiometabolic diseases in Africa: methods used for Phase 1 of the AWI-Gen population cross-sectional study

Abstract

There is an alarming tide of cardiovascular and metabolic disease (CMD) sweeping across Africa. This may be a result of an increasingly urbanized lifestyle characterized by the growing consumption of processed and calorie-dense food, combined with physical inactivity and more sedentary behaviour. While the link between lifestyle and public health has been extensively studied in Caucasian and African American populations, few studies have been conducted in Africa. This paper describes the detailed methods for Phase 1 of the AWI-Gen study that were used to capture phenotype data and assess the associated risk factors and end points for CMD in persons over the age of 40 years in sub-Saharan Africa (SSA). We developed a population-based cross-sectional study of disease burden and phenotype in Africans, across six centres in SSA. These centres are in West Africa (Nanoro, Burkina Faso, and Navrongo, Ghana), in East Africa (Nairobi, Kenya) and in South Africa (Agincourt, Dikgale and Soweto). A total of 10,702 individuals between the ages of 40 and 60 years were recruited into the study across the six centres, plus an additional 1021 participants over the age of 60 years from the Agincourt centre. We collected socio-demographic, anthropometric, medical history, diet, physical activity, fat distribution and alcohol/tobacco consumption data from participants. Blood samples were collected for disease-related biomarker assays, and genomic DNA extraction for genome-wide association studies. Urine samples were collected to assess kidney function. The study provides base-line data for the development of a series of cohorts with a second wave of data collection in Phase 2 of the study. These data will provide valuable insights into the genetic and environmental influences on CMD on the African continent.

Keywords: AWI-Gen; African populations; Cardiometabolic disease; H3Africa; burden of disease.

Figure 1.

Conceptual framework for Phase 1 of the AWI-Gen study. To begin to understand the cardiometabolic disease endpoints in the six sub-Saharan African communities, we collected data on non-modifiable biological factors and a host of mediators and potential confounders, including behavioural data and infection history and measures of body composition that include height, weight, waist and hip circumference (WC and HC), visceral and subcutaneous fat (VAT and SCAT) and carotid intima-media thickness (CIMT). Also measured were markers indicative of cardiometabolic disease (CMD) including blood pressure, glucose and insulin, urinary albumin protein and creatinine (UAPC) and serum creatinine (SC).

Figure 2.

Distribution of the AWI-Gen study participants across the six centres located in Nanoro (Burkina Faso), Navrongo (Ghana), Nairobi (Kenya), and Dikgale, Agincourt and Soweto in South Africa (SA). The pie charts represent the total numbers of female (orange segments) and male (blue segments) participants aged 40–60 years for each centre, and participants over the age of 60 years for Agincourt.

Figure 3.

Distribution of female (orange bars) and male (blue bars) study participants aged between 40 and 60 years across the six AWI-Gen centres, stratified according to age group 40–44, 45–49, 50–54 and 55–60 years.