| Summary: | 碩士 === 高雄醫學大學 === 公共衛生學系公共衛生學碩士班 === 105 === Introduction and objectives: Body Mass Index (BMI) is the most common use index of obesity currently; however, BMI provide no information on the distribution of adipose tissue, namely, we can’t distinguish general obesity and central obesity from BMI. Hence, many anthropometric related obesity indices were developed recently for better discrimination of cardiometabolic disorders. A Body Shape Index was first proposed by Krakuar & Krakuar in 2012 with the advantage of controlling potential confounders (BMI & height); nonetheless, a Portuguese study had found a counter-intuitive association between ABSI and blood pressure in adolescent which we think the body shape of adolescents is different from that of adults and, therefore, using the same set of scaling exponents introduces confounding. This study aims, first, whether the scaling exponents for standardizing WC for BMI and height in Taiwanese adolescents and compare them with the findings from the original ABSI. The second objective is to compare the ability to identify metabolic syndrome (Mets) and its factors among 12 obesity indices comprehensively.
Methods: There are two representative subjects in this study: Nutrition and Health Survey in Taiwan (NAHSIT) which was nationwide as development dataset and monitor Multilevel Risk Profiles for Adolescent Metabolic Syndrome (mRP-aMS study) from southern Taiwan as validation dataset, in order to evaluate the discrimination of Body Mass Index, Waist circumference, Hip circumference, Waist-to-Hip Ratio, Waist-to Height Ratio, Body Adiposity Index, Abdominal Volume Index, Conicity Index, Body Roundness Index, A Body Shape Index and two composite obesity indices (principle component 1 and 2; PC1 and PC2) found by principle component analysis. We used the criteria from International Diabetes Federation to diagnose adolescent Mets and area under the receiver operating characteristic curve to assess the discrimination; moreover, we picked up obesity indices of top 25% of discrimination by sorting rank sum. In this study, multiple logistic regression was used to calculate the odds ratio (OR) between 12 obesity indices and Mets.
Results: The original ABSI had high correlation coefficient in both NAHSIT and mRP-aMS research group (P <0.05), suggesting incapable of controlling those confounders. Sex had significant interaction on the relation of BMI and waist circumference (P for interaction <0.001). In NAHSIT research group showed the top 25% of discrimination obesity indices of male teenagers were BMI, AVI and BOYPC1 whose rank sum was 43, 40.5 and 40, respectively; meanwhile, GIRLPC1, WHtR, BRI and BMI were chosen in female teenagers and each of the rank sum was 40, 37, 37 and 35. Similar results were found in mRP-aMS research group, that was the top 25% of discrimination obesity indices in male teenagers were BMI, BOYPC1 and AVI, whose rank sum was 41, 38 and 37; while female teenagers had AVI, WHtR, BRI and GIRLPC1 and the rank sum was 39, 37, 37 and 34, repestively. BOYPC1 and GIRLPC1 had the highest Odds Ratio to Mets among 12 obesity indices (In NAHSIT dataset, BOYPC1, OR=1.86; GIRL-PC1=1.65; In mRP-aMS study, BOYPC1, OR=1.92, GIRLPC1=1.91, all P <0.001). Besides, ABSI developed from each research group had the lowest OR in Mets (In NAHSIT dataset, male OR=1.02, female OR=1.02；mRP-aMS study, male OR=1.01, female OR=1.02; all P ≤0.016).
Conclusion: We found ABSI should be modified the scaling exponents according to age, sex and different demographic characteristics population. As the indicators of discriminate Taiwan adolescents Mets, BMI and AVI were suitable for male teenagers; on the other hand, for female teenagers WHtR and BRI were appropriate. ABSI may not be an appropriate obesity index for adolescents. Moreover, BMI seems still to be an effective obesity index for identifying teenage cardiometabolic disorders. Because of the resemble discrimination for Mets and its factors in WHtR and BRI, we recommend WHtR due to simpler calculation. Composite obesity index was uneasy to explain, however, it had the highest OR for Mets and highlight the importance of concerning composite indices. ABSI may be inadequate for predicting Mets in adolescents. In addition, BMI which is currently used is still enough for identifying the Mets and its factors in Taiwan male adolescents.
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