Waist circumference thresholds predicting incident dysglycemia and type 2 diabetes in Black African men and women

ABSTRACT Objective To determine the waist circumference (WC) thresholds for the prediction of incident dysglycemia and type 2 diabetes in Black South African (SA) men and women and compare these to advocated International Diabetes Federation (IDF) Europid thresholds. Research design and method In this prospective study, Black SA men (n=502) and women (n=527) from the Middle Aged Sowetan Cohort (MASC) study who had normal or impaired fasting glucose at baseline (2011-2015) were followed up through 2017-2018. Baseline measurements included anthropometry, blood pressure and fasting glucose, HDL-cholesterol and triglyceride concentrations. At follow-up, glucose tolerance was assessed using an oral glucose tolerance test. The Youden index was used to determine the optimal threshold of WC to predict incident dysglycemia and type 2 diabetes. Results In men, the optimal WC threshold was 96.8 cm for both dysglycemia and type 2 diabetes (sensitivity 56 and 70%, specificity 74 and 70%, respectively), which performed similarly to the IDF threshold of 94 cm. In women, the optimal WC threshold for incident dysglycemia was 91.8 cm (sensitivity 86%, specificity 37%) and for type 2 diabetes was 95.8 cm (sensitivity 85%, specificity 45%). In comparison, the IDF threshold of 80 cm in women had higher sensitivity (97 and 100%), but lower specificity (12 and 11%) to predict incident dysglycemia and type 2 diabetes, respectively. Conclusions In this first prospective study of incident type 2 diabetes in Africa, we show that African-specific WC thresholds perform better than the IDF WC thresholds to predict incident dysglycemia and type 2 diabetes.