The initial study sample consisted of 1822 unrelated subjects from the Africa America Diabetes Mellitus (AADM) study (Rotimi et al., 2001 (link), 2004 (link)), a genetic epidemiology study of T2D in SSA. All subjects were SSA, enrolled from university medical centers in Nigeria, Ghana, and Kenya. Patients attending medical clinics at these medical centers or patients referred for clinical suspicion of diabetes were evaluated for potential inclusion in the study as described below. After providing informed consent, all participants underwent a clinical examination that included a medical history, clinical anthropometry, blood pressure measurements and blood sampling. Weight was measured in light clothes on an electronic scale to the nearest 0.1 kg, and height was measured with a stadiometer to the nearest 0.1 cm. Body mass index (BMI) was computed as weight in kg divided by the square of the height in meters. The other clinical measurements have been described elsewhere (Rotimi et al., 2001 (link), 2004 (link)). The definition of T2D was based on the American Diabetes Association (ADA) criteria: a fasting plasma glucose concentration (FPG) ≥ 126 mg/dl (7.0 mmol/l) or a 2-h postload value in the oral glucose tolerance test ≥ 200 mg/dl (11.1 mmol/l) on more than one occasion. Alternatively, a diagnosis of T2D was accepted if an individual was on pharmacological treatment for T2D and review of clinical records indicated adequate justification for that therapy. The detection of autoantibodies to glutamic acid decarboxylase (GAD) and/or a fasting C-peptide ≤ 0.03 nmol/l was used to exclude probable cases of type 1 diabetes. Controls were required to have FPG < 110 mg/dl or 2-h postload of < 140 mg/dl and no symptoms suggestive of diabetes (the classical symptoms being polyuria, polydipsia, and unexplained weight loss).
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