Body mass index, waist circumference and waist-to-hip ratio cut-off points for categorisation of obesity among Omani Arabs

Background.- There are no data on optimal cut-off points to classify obesity among Omani Arabs. The existing cut-off points were obtained from studies of European populations. Objective: To determine gender-specific optimal cut-off points for body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WER) associated with elevated prevalent cardiovascular disease (CVD) risk among Omani Arabs. Design: A community-based cross-sectional study. Setting: The survey was conducted in the city of Nizwa in Oman in 2001. Subjects and methods: The study contained a probabilistic random sample of 1421 adults aged >= 20 years. Prevalent CVD risk was defined as the presence of at least two of the following three risk factors: hyperglycaemia, hypertension and dyslipidaemia. Logistic regression and receiver-operating characteristic (ROC) curve analyses were used to determine optimal cut-off points for BMI, WC and WHR in relation to the area under the curve (AUC), sensitivity and specificity. Results: Over 87% of Omanis had at least one CVD risk factor (38% had hyperglycaemia, 19% hypertension and 34.5% had high total cholesterol). All three indices including BMI (AUC = 0.766), WC (AUC = 0.772) and WHR (AUC = 0.767) predicted prevalent CVD risk factors equally well. The optimal cut-off points for men and women respectively were 23.2 and 26.8kg m(-2) for BMI, 80.0 and 84.5 cm for WC, and 0.91 and 0.91 for WHR. Conclusions: To identify Omani subjects of Arab ethnicity at high risk of CVD, cutoff points lower than currently recommended for BMI, WC and WHR are needed for men while higher cut-off points are suggested for women.