Identifying cut-points in anthropometric indexes for predicting previously undiagnosed diabetes and cardiovascular risk factors in the Tongan population

SummaryThere is growing concern that a single standard definition of overweight and obesity may not suit all ethnic groups. This study aimed to evaluate different anthropometric cut-points as indicators of risk for Type 2 diabetes (T2DM), hypertension and dyslipidaemia in a cross sectional, representative sample of the population of the Kingdom of Tonga (767 subjects: 314 males, 453 females). Anthropometric measurements included weight, height, waist circumference (WAIST), waist-to-hip ratio (WHR), weight-to-height ratio (WhgtR) and percentage body fat (%fat) using bioelectrical impedance. Risk factors investigated were systolic (sBP) and diastolic blood pressure (dBP), plasma glucose, total cholesterol, HDL cholesterol and triglycerides, hypertension and T2DM. The best predictive cut-points were identified using receiver operating characteristic (ROC) curves.The cut-points identified in this cross-sectional study contrast with those from studies in Caucasian and Asian populations. Optimal cut-points for predicting risk for T2DM, dyslipidaemia and hypertension in men were 29.3–31.7 kg/m2 for BMI; 98.8–102.9 cm for WAIST; 0.91–0.93 for WHR and 0.56–0.60 for WhgtR. For women, the cut-points were 34.0–35.0 kg/m2 (BMI), 100.0–102.8 cm (WAIST), 0.83–0.86 (WHR) and 0.60–0.62 (WhgtR). Mean area under the curve (AUC) measurements for each index ranged between 0.57 and 0.75 for men and 0.49 and 0.72 for women. The indexes with the highest AUCs for men were WAIST, WhgtR and BMI; and for women were WAIST and WhgtR. Use of a 100 cm tape for measuring WAIST is recommended as a simple public health and clinical indicator of risk until longitudinal follow-up studies can confirm findings of this study.