Abstract P141: Detection of Abnormal Glucose Tolerance in Africans: International Diabetes Federation Waist Circumference Thresholds Perform Better in Africans Than the Higher Thresholds Used in America
Authors: Jean D Kabakambira, Sara M Briker, Rafeal L Baker, Amber B Courville, Francine Thomas, Lilian S Mabundo, Stephanie T Chung, Christopher W DuBose, Mizanur Rahman, Anne E Sumner
Journal: Circulation (2018)

Introduction: In the 21 st century, Africans are experiencing an epidemic of diabetes and heart disease. Key to addressing this public health challenge is the identification of thresholds for risk factors for diabetes and heart disease which are valid in Africans. For example, central obesity indicates both insulin resistance (IR), a risk factor for heart disease, and abnormal glucose tolerance (abnl-GT), a term which encompasses both prediabetes and diabetes. There are two major standards for diagnosing central obesity by waist circumference (WC): the European standard of the International Diabetes Federation (IDF) (men: 94 cm, women: 80 cm) and the American standard of the AHA/NHLBI (men: 102 cm, women: 88 cm). It is unknown if either the IDF or higher AHA/NHLBI thresholds are appropriate for Africans. Objectives: Our goals were to determine in Africans the WC that best predicts IR and abnl-GT and then compare these thresholds to the standards put forward by the IDF and AHA/NHLBI. Methods: We measured WC and determined glucose tolerance status by the OGTT in 348 subSaharan Africans (male 69%, age 39±10y (mean±SD) range 20 to 64y, BMI 27.6±0.2, (range 18.2 to 42.4) who were living in America, born in Africa (West: 51%, Central: 23%, East: 26%) and self-identified as healthy. The area under the receiver operating characteristic curve (AUC-ROC) and the Youden Index were used to determine the WC which best predicts IR and abnl-GT. IR was defined by the lowest tertile of the Matsuda Index. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were measured by computerized tomographic scan. Prior to analyses, the participants were divided into 4 groups: (1) normal glucose tolerant (NGT), (2) NGT and IR, (3) abnl-GT and IR, (4) abnl-GT and no IR. Results: The prevalence of these 4 groups did not differ by sex and their overall frequency were: 47% with NGT; 13% with NGT and IR ;19% with abnl-GT and IR; and 21% with abnl-GT and no IR. BMI was higher in women than men (28.5±5.4 vs. 27.2±3.9, P=0.01). After adjusting for BMI, women had lower WC and VAT and higher SAT than men (all P &lt; 0.001). According to the Youden Index, the optimal WC in men which predicted IR and abnl-GT were: 91 cm (AUC-ROC±SE 0.78±0.03) and 92 cm (0.67±0.04), resp. In women, the optimal WC which predicted IR and abnl-GT were: 96 cm (0.75±0.05) and 82 cm (0.67±0.06), resp. Conclusions: Gender differences in body fat distribution may explain why in women, but not men, the WC which predicts IR was higher than the WC which predicts abnl-GT. However, and most importantly, the WC thresholds which optimally predict abnl-GT in African men and women were much more similar to the IDF(men: 94 cm, women: 80 cm) than the higher AHA/NHLBI (men: 102 cm, women: 88 cm) thresholds. Therefore, we recommend that WC thresholds from the IDF be used to screen African men and women for abnl-GT.