Obesity is a recognized risk factor for numerous disease states, including T2D. Its prevalence in China, as well as the world, has become a major public health concern [20
]. Although obesity is well recognized, T2D often goes undetected [11
] until patients present with diabetic complications. Anthropometric measures are a simple and useful tool that can be used to screen for T2D. Although imaging techniques can accurately quantify body fat and predict metabolic abnormalities, it is impractical for routine clinical practice [21
]. The Diabetes Prevention Program sub study showed that visceral fat measured by CT provided no significant advantage over simple measures in predicting the development of diabetes [5
]. Therefore, the use of anthropometric measures is an alternative for rural general practitioners to assess the risks of their patients quickly, easily and inexpensively.
There has been much discussion and no clear consensus on which obesity measure is the most sensitive or specific for detecting diabetes. Previous studies comparing WC, BMI and WHR have been inconsistent [6
] with few studies addressing these issues in the Chinese population. The aim of this study is to compare the use of these anthropometric markers in Chinese individuals and determine the best obesity indicators. Analysis of ROC curves demonstrated that WC, WHTR and BMI in men were similar, with WHR being the weakest indicator. However, in women, WC, WHR and WHTR were significantly better than BMI. These findings suggest that WC and WHTR perform significantly better than others for identifying T2D irrespective of gender. However, WC is easier to be obtained and understood than WHTR. Therefore, we chose WC to be a superior tool for discriminating obesity related T2D risk evaluation in Chinese population.
Our data among the Chinese population is supported by the literature. Wannamethee et al. showed that WC and BMI had similar predictive risks for T2D in older European men, whereas WC was a superior predictor in women [22
]. Among the ethnically diverse population studied in the Diabetes Prevention Program, increased WC was the most significant predictor of diabetes in men and women in the lifestyle and placebo groups [5
]. The Healthy Twin Study showed WC, WHTR, and BMI were consistently associated with all metabolic risk factors regardless of the subject’s gender in Korean population [10
]. Additionally, WC is recommended by the US National Institutes of Health clinical guidelines for the assessment or management of obesity [23
], and compared to WHTR, WHR and BMI, WC is not affected by measurement errors and does not require any calculations. Therefore, we recommend WC as the best obesity measure in T2D risk evaluation for the Chinese population.
The cut-off point for the WC recommended for use in clinical practice also remains controversial [24
]. Different WC cutoff values are recommended for different ethnicities [25
]. Several studies have examined appropriate cutoffs for abdominal obesity in Chinese population. Zhou et al’s study showed a waist circumference greater than 85
cm for men and 80
cm for women were recommended as the cut-off points for central obesity [2
]. Bao Y et al’s study showed the optimal cutoff point of waist circumference that positively correlated with the risk of MetS is 90
cm for men and 85
cm for women [13
]. A study found that sensitivity equaled specificity for diabetes suggested a waist circumference cutoff of 80
cm for both men and women [26
]. However, a limitation of the study included patients with undiagnosed and diagnosed diabetes without performing an OGTT. Our data indicated optimal discrimination for diabetes for WC thresholds to be 86
cm in women and 90
cm in men. The influence of abdominal fatness on a health risk such as T2D is a continuous one, and thus, any cutoffs may be arbitrary [6
Those recommended based on our data were identified as the values of the WC that best balanced sensitivity and specificity. This decision rule accommodates the desire to prevent a significant risk of diabetes. Our cut-off points identify risk factors with a sensitivity greater than 70% and specificity greater than 50%. It can offer an alert about the practical boundary for initiating intervention to prevent and control the increase in the risk factor of T2D as early as possible.
There are several potential limitations in this study. First, it is a cross-sectional study, and we cannot draw conclusions about cause and effect relationships between WC and T2D. Secondly, there are variations in the WC and BMI among Chinese in different regions. People living in the northern area have larger WC and BMI than those in the eastern, western and southern areas of China [27
]. Our subjects were selective to the northern regions of China and therefore our results may not represent the whole population. Further research on other regions in China will be needed to identify the best cutoff of T2D and anthropometric indices. Finally, not all subjects performed OGTT. Therefore, it is possible that the frequency of T2D had been under-estimated.