Optimal Cut-off Points Of Waist Circumference For Detecting Central Obesity And Severe Central Obesity In Chinese Adults

ObjectiveWaist circumference is a major indicator of abdominal fat accumulation as well as a well-accepted index of central obesity. Given that no consensus has yet been reached over the optimal cut-off points of waist circumference (WC) for Chinese, this study aimed to determine the appropriate cut-off points of WC for detecting central obesity and severe central obesity in a Chinese adult population.MethodsData from the cross-sectional survey of the People’s Republic of China-United States Collaborative Study of Cardiovascular and Cardiopulmonary Epidemiology in 1993-1994 was used, including 10 265 subjects (4 921 men and 5 344 women) aged 35-69 years. Hypertension, diabetes mellitus (DM), hypercholesterolemia, hypertriglyceridemia and low levels of high-density lipoprotein cholesterol were regarded as major cardiovascular disease (CVD) risk factors. Each integer of WC in centimeters in a given range (75～100 cm for men,70～95 cm for women) was used as the cut-off point to detect each of the five risk factors and clustering of risk factors, which was defined as the presence of two or more risk factors in an individual. Sensitivity, specificity and distance from the receiver operating characteristic (ROC) curves to the upper left corner of the ROC graph were calculated. For detecting clustering of CVD risk factors, the WC value corresponding to the point on the ROC curve nearest to the upper left corner of the ROC graph was considered the optimal cut-off for central obesity and the value corresponding to the point with specificity of 90% or more was considered the optimal cut-off for severe central obesity. The age-adjusted odds ratio (OR) and the population attributable risk proportion (PARP) were calculated for subjects with higher WC levels than the optimal cut-off points.ResultsThe mean waist circumference was 80.5 ± 9.9 cm in men and 77.8 ± 10.0 cm in women; 18.1%(890/4921) of men and 14.5%(776/5 344) of women were identified with two or more major cardiovascular risk factors. The prevalence of all five major risk factors increased with increasing WC levels in both men and women (all P for trend <0.05). The ROC curve analysis showed that the optimal cut-off value of WC to detect clustering of risk factors was ≥84 cm for men and was ≥80 cm for women with the shortest distance to the upper left corner being 0.430 4 and 0.450 4, respectively. The cut-off values of WC with specificity above 90% were ≥93 cm and ≥91 cm for men and women respectively. The optimal cut-off values of WC for detect each of the five risk factors were 80～84 cm for men and 79～81 cm for women. According to the PARP analysis, reducing WC to the recommended levels (WC<85/80 cm for men/women) could prevent approximately 45～48% of hypertension,39～45% of DM and 57～59% of clustering of cardiovascular risk factors.ConclusionsThese results were equal or similar to the WC cut-off points proposed by the Guidelines for Prevention and Control of Overweight and Obesity in Chinese Adults, i.e., ≥85/80 cm (men/women) for increased risk for obesity related diseases and ≥95/90 cm (men/women) for much higher risk. For practical reasons, WC≥ 85/80 cm and ≥ 95/90 cm (men/women) could be the optimal cut-off values for detecting central obesity and severe central obesity, respectively, in Chinese adult population.