Cross-validation Of The Developed Obesity Cut-off Points For Korean Adults

Abstract

PURPOSE: Establishing valid criteria for the diagnosis of obesity is important for screening and treating obesity-related disorders. Several different cut-off points (CP) have been developed for obesity to predict cardiovascular disease risk factors (CDRF) such as hypertension, dyslipidemia, and diabetes mellitus (DM) in Korean adults; however, there are no cross-validation studies for the developed obesity CP. Therefore, the aim of this study is to examine the diagnostic accuracy of obesity CP. METHODS: Data (9,425 adults [≥18 years], male = 4,031) from the 2008 and 2011 Korea National Health and Nutrition Examination Survey was analyzed to examine the accuracy of obesity CP developed using three obesity indices: body mass index (BMI; 23, 24, 25, & 26kg/m2), waist circumference (WC; 84, 85, & 90cm for male; 78, 80, & 85cm for female), and body fat percentage (BF%; 20, 21, & 26 for male; 36 & 37 for female). Participants with CDRF were operationally defined as having one or more of the followings; hypertension, dyslipidemia, and/or DM. CP of BMI, WC, and BF% were evaluated using Youden Index (YI; sensitivity [SE] + specificity [SP] - 1). To evaluate the CP with highest YI, adjusted odds ratios (OR) of having CDRF were calculated while controlling for age, sex, physical activity status, smoking, alcohol consumption, household income, and education level. RESULTS: Overall, SE and SP of the CP were low across three obesity indices (SE=29.26-75.86%, SP=46.51-85.98%). CP with highest YI were BMI of 23 (SE=69.25%, SP=53.21%), WC of 84 (SE=62.68%, SP=66.67%), and BF% of 20 (SE=75.86%, SP=46.51%) and BMI of 23 (SE=66.74%, SP=64.86%), WC of 78 (SE=69.52%, SP=67.89%), and BF% of 35 (SE=50.73%, SP=69.64%) for male and female, respectively. Obese adults were more likely to have CDRF compared to none-obese adults (OR=2.61-2.96, 95% CI=2.19-3.63 for male; OR=2.05-3.00, 95% CI=1.69-3.60 for female, respectively). CP of WC had the highest YI and OR while the CP of BF% had the lowest for both male and female. CONCLUSIONS: WC of 84cm for male and 78cm for female were identified as the best obesity CP to predict CDRF for Korean adults. The overall diagnostic accuracy (i.e., SE and SP) of the obesity CP, however, was performed poorly. Therefore, caution is necessary when using the developed obesity CP.