Obesity indices versus 2-hour plasma glucose for predicting incident diabetes in a 16-year prospective study of Hong Kong Chinese

Abstract

Obesity is an established risk factor of type 2 diabetes. Here we investigated in a relatively non-obese, community-based Hong Kong Chinese Cohort, whether obesity indices could replace glycemic measures in predicting incident diabetes, in a 16-year prospective study. We studied 1505 subjects from the Hong Kong Cardiovascular Risk Factor Prevalence Study (CRISPS) who were non-diabetic at baseline (CRISP1: 1995-6), but had diabetes at follow-up assessments: CRISP2 (2000-4), and/or CRISP3 (2005-8), and/or CRISP4 (2010-2); or were confirmed non-diabetic by CRISP4. Glycemic status was tested by 75g OGTT at baseline and follow-up visits. Incident diabetes was defined as FG ≥ 7 mmol/L or 2hG ≥ 11.1 mmol/L or use of anti-diabetic agents. By CRISP4, 281 participants had developed diabetes while 1224 remained non-diabetic. On multiple logistic regression including either body mass index (BMI), waist circumference (WC) or waist-hip-ratio (WHR) in the model, the most significant predictors of incident diabetes (all p<0.001) were, in order of standardized odds-ratios, baseline 2hG, BMI or WC, FG and triglyceride levels. Other significant predictors included age (p=0.001), smoker (p=0.009), hypertension (p=0.033), sex (p=0.037) and WHR (p=0.046). Their performance in diabetes prediction was assessed by the area under the curve (AUC) of ROC (receiver-operator curve) analysis. The AUC-ROC of BMI and WC were 0.732 and 0.733 respectively, being less favorable than 2hG (0.799; p<0.002; DeLong) but comparable to FG (0.714; p>0.3). However, the AUC-ROC of BMI + age (0.773) or WC in women (0.749) did not differ significantly from 2hG. The optimal cut-off by Youden J index for BMI, WC (women) and age were >24.5 kg/m2, >79 cm and >45 years respectively. In conclusion, BMI and age or, in women, WC alone, can potentially replace the use of the OGTT to identify subjects at increased risk of diabetes in our population for intensified preventive measures by life-style modification.