Overweight and Obesity Among Primary Schoolchildren in Nakhon Pathom, Thailand: Comparison of Thai, International Obesity Task Force and Who Growth References
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SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH OVERWEIGHT AND OBESITY AMONG PRIMARY SCHOOLCHILDREN IN NAKHON PATHOM, THAILAND: COMPARISON OF THAI, INTERNATIONAL OBESITY TASK FORCE AND WHO GROWTH REFERENCES Seo Ah Hong1,2, Chawewan Sriburapapirom1, Kriengsak Thamma-aphiphol1, Chutima Jalayondeja3 and Sariyamon Tiraphat1 1ASEAN Institute for Health Development, Mahidol University, Nakhon Pathom, Thailand; 2Institute for Health and Society, Hanyang University, Seoul, Republic of Korea; 3Faculty of Physical Therapy, Mahidol University, Nakhon Pathom, Thailand Abstract. Differences in estimation of over-nutrition due to use of different clas- sification methods lead to difficulty in comparison. This study determined preva- lence of overweight and/or obesity using different criteria and their relationship to socio-demographic determinants. A total of 605 schoolchildren (Grades 4-6) in Nakhon Pathom, Thailand were assessed for overweight and/or obesity based on Thai Growth Reference (TGR), WHO Growth Reference (2006) and International Obesity Task Force (IOTF) (2012). Prevalence of combined overweight and obesity ranged from 23.1% using TGR to 37.2% using WHO Growth Reference. Prevalence of obesity showed better concordance among the three methods, ranging from 11.5% using IOTF to 17% using WHO Growth Reference and TGR. All methods showed good agreement, with the highest being between TGR and IOTF (Kappa = 0.81; 95% CI: 0.76-0.87 in boys and 0.76; 95% CI: 0.68-0.83 in girls). Boys, children of mothers with high body mass index and having no sibling were more likely to be overweight or obese, regardless of the methods used. Our results show marked differences in prevalence of overweight and/or obesity estimated by these three classifications, and the impact of the choice of classification system should be considered with caution according to the purpose of the estimation. Keywords: obesity, overweight, prevalence, primary schoolchildren, socio- demographic factor, Thailand INTRODUCTION type II diabetes, increased cardiovascular risk factors, sleep apnea, and psychosocial As childhood obesity is associated problems (WHO, 2000) and contributes to with a number of health problems, such as increases in mortality and morbidity in the long term, it has been one of the most seri- Correspondence: Seo Ah Hong, ASEAN Insti- ous public health challenges (WHO, 2000). tute for Health Development, Mahidol Univer- sity, Salaya, Phutthamonthon, Nakhon Pathom Indeed, it has reported that with increas- 73170, Thailand. ing prevalence of obesity in both children Tel: +66 (0) 2441 9040-3 ext 16; Fax: +66 (0) and adults in Thailand (Jitnarin et al, 2011; 2441 9044 Yamborisut and Mo-Suwan, 2014), morbid- E-mail: [email protected] ity of type 2 diabetes has increased from 902 Vol 48 No. 4 July 2017 OVERWEIGHT AND OBESITY AMONG THAI SCHOOLCHILDREN 5% during 1986-1995 to 17.9% during 1996- in Thai schoolchildren. Hence, the aims of 1999 among Thai children (Likitmaskul this study were to determine the preva- et al, 2003) and total socio-economic cost lence of overweight and obesity using the of overweight and obesity accounts for three different methods and to investigate 0.13% of Thailand’s GDP (Pitayatienanan whether socio-demographic factors of et al, 2014). Thailand to the prevalence are the same As childhood obesity tends to persist for the different criteria used. This study into adulthood (Guo et al, 2002), diagnosis may provide insights into whether and of overweight and obesity in childhood under what circumstances a national or is of important relevance to public health international growth reference standard (Daniels et al, 2005). Methods such as dual- is most useful for schoolchildren. energy X-ray absorptiometry are more accurate for measuring adiposity, but are MATERIALS AND METHODS of limited applicability for population Study group screening (WHO, 2000). Therefore, for population screening or for epidemiologic This cross sectional study was con- research, using a weight/height index to ducted in a group of 605 schoolchildren define obesity has advantages that out- (Grades 4 to 6; 9-12 years old) attending weigh its limitations. two primary schools in Nakhon Pathom, Thailand in 2015. Prior to undertaking the Many studies in Thailand have used study, the study design and purpose were the national Thai Growth Reference (TGR) discussed with the Director of each school developed from a cross-sectional study of and their approvals were obtained. Prior children and adolescents from birth to 19 informed consents were granted from the years of age in urban areas of 17 provinces parents/legal guardians after explanation in 1999 (Yamborisut and Mo-Suwan, 2014). of the study objectives, and assurance of For a global cut-off to define overweight or confidentiality and that choosing not to obesity, WHO Growth Reference (WHO, participate would not disadvantage their 2006; de Onis et al, 2007) and the Interna- children in any way. All procedures were tional Obesity Task Force (IOTF) (Cole et al, approved by the Human Research Ethics 2000; idem, 2007) are generally accepted for Committee of Mahidol University (ap- making appropriate comparisons across proval no. 2015/033.2701). studies and monitoring global obesity epidemic because the cut-off values are Measurements and statistical analysis comprehensive, available and easy to be Children were asked to wear light used. However, differences in estimation indoor clothing without shoes for mea- of overweight and obesity due to the use of surements. Weight was measured to the different classification methods can make nearest 100 g using a digital weight scale it difficult to monitor national and global and standing height was measured to trends, to perform comparisons among the nearest 0.5 cm using a wall-mounted studies, and for employment in public wooden ruler. Assessment of overweight health and clinical settings (Neovius et al, or obesity was based on the indicators 2004). shown in Table 1. To the best of our knowledge, a lim- Concordance among the three di- ited effort has been made to compare the agnostic criteria for normal weight, application of these classification systems overweight and obesity was assessed by Vol 48 No. 4 July 2017 903 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH 904 Table 1 Classifications of overweight and obesity in Thai children. Variable Thai Growth Reference IOTF Growth Reference WHO Growth Reference Source Institute of Nutrition, Mahidol Cole and Lobstein (2012) WHO and NCHS University and Ministry of Public Health, Thailand. Data and reference A cross sectional study of breast- Large survey data sets from Brazil, Non-obese US subjects with expected population and predominantly formula-fed Britain, Hong Kong, Singapore, height from 1977 NCHS/WHO refer- children and adolescents from birth The Netherlands and USA (Cole ences (WHO, 1995), supplemented to 19 years of age in urban areas of et al, 2000; Cole and Lobstein, 2012). with data from WHO Child Growth 17 provinces in 1999 (Ministry of Standards (WHO, 2006) (to facilitate Public Health Thailand, 1999). a smooth transition at 5 years of age) (de Onis et al, 2007). Age group 0-19 years 2-18 years 5-19 years Classification method Age- and gender-specific weight- New age- and gender-specific BMI Age- and gender-specific BMI Z for children 9-12 years for-height Z (WHZ) score (INMU, cut-offs defined in terms of the scores estimated using AnthroPlus of age. 2002). percentiles at 18 years of age cor- (WHO, 2009). responding to each BMI value in 2012 (Cole and Lobstein, 2012). Overweight Age- and gender-specific WHZ Age- and gender-specific BMI cut- Age -and gender-specific BMI >85th score >1.5 SD to 2 SD of median. offs derived from BMI-age curves percentile or +1 SD score. >BMI of 25 at 18 years of age. Obese Age- and gender-specific WHZ > 2 Age- and gender-specific BMI cut- Age- and gender-specific BMI >95th SD of median. offs derived from BMI-age curves percentile or +2 SD score. >BMI of 30 at 18 years of age. Vol 48 No. 4 July 2017 OVERWEIGHT AND OBESITY AMONG THAI SCHOOLCHILDREN weighted Cohen’s Kappa (k) coefficient, age were different between genders (Table together with its 95% confidence interval 2). In boys, prevalence of combined over- (CI). In addition, in order to identify fac- weight and obesity decreased with age tors associated with obesity alone and until year 11 and then slightly increased at combined overweight and obesity, logis- years 12 regardless of the methods used. tic regression analysis was conducted to In girls, this did not change much with age estimate Odds ratios (OR) and 95% CI until year 11 regardless of the methods, for each of the three classification criteria but dramatically rose at year 12 when (TGR, WHO Growth Reference and IOTF using TGR only (24%). As regards obesity cut-offs) (all variables being modeled alone, while a decrease in prevalence with simultaneously). Statistical analysis was age was apparent in boys, particularly conducted using SAS for Windows, ver- when using international growth refer- sion 9.3 (SAS Institute, Cary, NC). ences, in girls, the prevalence tended to decrease until year 11, regardless of the RESULTS methods used, but the prevalence at year 12 depended on the growth reference Prevalence of overweight and/or obe- used: 10% using IOTF, 15% using WHO sity among Thai children aged 9-12 years Growth Reference and 21% using TGR. were determined according to the three Combined overweight and obesity classification methods. Obesity preva- and obesity alone were elevated in boys, lence was lower when using IOTF (16% children of mothers with high body mass in boys and 8% in girls) compared to the index (BMI), and those with no sibling, other two methods (TGR: 24% in boys and regardless of the classification system 11% in girls; WHO Growth Reference: 26% used (Table 4).