Body Mass Index, Waist Circumference and Cut-Off Points for Metabolic Syndrome in Urban Residents in Ningxia

A growing number of studies show that different countries and populations require different cut-off points for body mass index (BMI), and waist circumference (WC) leading to obesity. There are no data on optimal cut-off points to metabolic syndrome (MS) among urban residents in Ningxia. Our aim is to determine the appropriate cut-off points for BMI and WC associated with elevated prevalent MS risk among urban residents in Ningxia. A total of 2500 urban residents in Ningxia were examined from May 2008 to March 2009 in a community-based cross-sectional study. Height, body weight, waist circumference and hip circumference were measured to calculate BMI. Fasting blood glucose (FBG), plasma levels of triglyceride (TG), total cholesterol (TC), and highdensity lipoprotein cholesterol (HDL-C) were examined using a blood glucose meter and the chromatographic enzyme method. BMI and WC were measured to assess overweight or obesity. Of these, 301 subjects were chosen according to metabolic syndrome diagnosis standards to form the case group. The control group comprised 301 healthy people without diabetes, hypertension, hyperlipemia, coronary heart disease, cerebrovascular disease, malignant tumors or chronic infections. Logistic regression and receiver-operating characteristic (ROC) curve analyses were used to determine optimal cut-off points for BMI and WC in relation to the area under the curve (AUC), sensitivity and specificity. The optimal cut-off points for male and female respectively were 24.78 kg/m2 (sensitivity = 0.879, specificity = 0.648) and 24.72 kg/m2 (sensitivity = 0.804, specificity = 0.767) for BMI, 85.95 cm (sensitivity = 0.701, specificity = 0.641) and 78.25 cm (sensitivity = 0.804, specificity = 0.528) for WC. Urban residents in Ningxia were at high risk of MS, and the cut-off points for BMI and WC were lower than the data currently recommended in Asian population.