Abstract
BACKGROUND: The incidence of type 2 diabetes in sub-Saharan Africa is expected to increase, but few longitudinal studies have characterised its risk factors. This study aimed to determine the incidence of type 2 diabetes over 33 481 person-years and identify its principal risk factors in middle-aged adults (ie, those aged 40-60 years) from four sub-Saharan African countries. METHODS: Longitudinal data were available from 6553 participants aged 40-60 years at baseline from study centres in South Africa, Kenya, Ghana, and Burkina Faso. Sociodemographic, behavioural, clinical, and biochemical data were collected at baseline and after an interval of 5-6 years. The prevalence of type 2 diabetes was determined at each timepoint and diabetes incidence was calculated. A two-stage individual participant data meta-analysis was used to identify baseline risk factors for incident diabetes. FINDINGS: The overall incidence of type 2 diabetes was 14·6 (95% CI 13·4-16·0) cases per 1000 person-years. The incidence was highest in South Africa with 21·8 (19·5-24·4) cases per 1000 person-years, and lowest in west Africa with 5·5 (4·4-6·9) cases per 1000 person-years. Baseline glucose (adjusted odds ratio 1·37; 95% CI 1·16-1·42), being male (1·32; 1·12-1·54), family history of type 2 diabetes (1·22; 1·01-1·46), unemployment (1·19; 1·03-1·37), hypertension (1·21; 1·01-1·45), BMI (1·03; 1·02-1·04), and waist circumference (1·02; 1·01-1·03), were associated with a higher risk of incident type 2 diabetes, while adequate baseline physical activity (0·87; 0·76-1·00) was associated with lower risk. INTERPRETATION: The high incidence of type 2 diabetes in this middle-aged sub-Saharan Africa population is influenced by several modifiable risk factors that should inform interventions to mitigate the disease burden. FUNDING: National Institutes of Health, Department of Science and Innovation (South Africa), and the South African Medical Research Council.