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Prevalence of metabolic syndrome and factor analysis of cardiovascular risk clustering among adolescents in Ho Chi Minh City, Vietnam
Preventive Medicine 55 (2012) 409–411
Contents lists available at SciVerse ScienceDirect
Preventive Medicine journal homepage: www.elsevier.com/locate/ypmed
Brief Original Report
Prevalence of metabolic syndrome and factor analysis of cardiovascular risk clustering among adolescents in Ho Chi Minh City, Vietnam Tang Kim Hong a,⁎, Nguyen Hoang Hanh Doan Trang a, b,⁎, Michael J. Dibley b a b
Department of Community Health, Pham Ngoc Thach University of Medicine, Ho Chi Minh City, Viet Nam Sydney School of Public Health, Sydney Medical School, University of Sydney, NSW 2006 Australia
a r t i c l e
i n f o
Available online 10 September 2012 Keywords: Metabolic syndrome Cardiovascular risk factors Adolescents
a b s t r a c t Objective. This study aimed to describe the prevalence of metabolic syndrome (MetS) in adolescents of Ho Chi Minh City (HCMC) and to identify components of cardiovascular risk clusters. Methods. A cross-sectional study was conducted on a representative sample of 693 high-school students 13 to 16 years old in 2007. MetS was defined according to five different definitions: the Pediatric International Diabetes Federation, the Adult Treatment Panel III, and the modified definitions by Cook, Weiss, and De Ferranti. Principal components analysis (PCA) was carried out to cluster risk factors. Results. The prevalence of MetS was high and varied from 3.9% to 12.5%, depending on the criteria used. High levels of triglycerides (or low High Density Lipoprotein Cholesterol) and high blood pressure were the most prevalent components of MetS, while impaired glucose tolerance was the least prevalent. PCA showed three factors in boys (obesity, hypertension, dyslipidemia) that cumulatively explained 64.3%, and four factors in females (obesity, hypertension, dyslipidemia, and hyperglycemia) that accounted for 73.6% of the observed variance of MetS. Conclusions. The prevalence of MetS in HCMC adolescents was high. Obesity accounts for the maximum variance in clustering and appears to be a more powerful correlate of cardiovascular risk than other variables. © 2012 Elsevier Inc. All rights reserved.
Introduction Metabolic syndrome (MetS) is rapidly increasing worldwide in children and adolescents, in-line with rising childhood obesity and a sedentary life style (Cruz and Goran, 2004; Weiss et al., 2004). It is becoming a growing public health issue (Zimmet et al., 2007a), especially in developing countries, where the prevalence of chronic diseases is rising far more rapidly in comparison to developed nations (Yusuf et al., 2001). In Vietnam, adolescent obesity is emerging as an important health problem (Hong et al., 2007); however, there is no report of MetS in adolescents. A unified definition of MetS for adolescents is lacking. Different cut-offs including the National Cholesterol Education Program Adult Treatment Panel III (ATP III) criteria (Anon, 2002) adapted by Cook et al. (Cook et al., 2003), by Weiss et al. (Weiss et al., 2004), by De Ferranti et al. (de Ferranti et al., 2004), and the Pediatric International Diabetes Federation (IDF) (Zimmet et al., 2007b) have been used to assess MetS prevalence in adolescents (Kong et al., 2008; Park et al., 2009; Singh et al., 2007). This study was undertaken to describe the prevalence of MetS and identify the clustering of components of risk
⁎ Corresponding authors at: Pham Ngoc Thach University of Medicine, 86/2 Thanh Thai Street, District 10, Ho Chi Minh City, Viet Nam. Fax: +84 8 9574 474. E-mail address: [email protected] (T.K. Hong). 0091-7435/$ – see front matter © 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ypmed.2012.09.002
variables associated with MetS in an urban population of Vietnamese adolescents from Ho Chi Minh City. Methods A cross-sectional assessment was conducted in 2007 on urban highschool students of Ho Chi Minh City. This sample was recruited for a cohort study started in 2004 (Trang et al., 2012). The study was approved by the ethics committee of Pham Ngoc Thach University of Medicine. Written consent was obtained from both students and their parents prior to data collection. Weight was measured without shoes and heavy clothes, using a Tanita electronic scale and was recorded to the nearest 0.1 kg. Standing height was taken with a suspended Microtoise tape to the nearest 0.1 cm. Waist circumference (WC) was measured to the nearest 0.5 cm with a non-elastic tape applied at a point midway between the lower border of the rib cage and the iliac crest. Fasting blood samples of 5 ml were taken in the morning at the subject's school by a trained laboratory technician. On the previous day, the students were instructed to fast for 12 h before the test. Blood specimens were kept in ice at 0 °C before being transported back to the Laboratory of the Diagnostic Center of Ho Chi Minh City for further processing. Serum lipid and glucose concentrations were measured and read on a BM/Hitachi 917 analyzer (Roche Diagnostics, IN, USA). Systolic and diastolic blood pressures (BP) were measured with an Omron BP monitor after 15 min of rest. This kind of device has been validated for BP measurement in adolescents (Christofaro et al., 2009) and the cuff used was recommended by the American Heart Association (Pickering et al.).
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T.K. Hong et al. / Preventive Medicine 55 (2012) 409–411
The subjects were classified as overweight/obese by applying the age- and sex‐specific International Obesity Task Force (IOTF) BMI cut-offs (Cole et al., 2000), and classified as having MetS according to five different definitions: the Pediatric IDF (Zimmet et al., 2007b), ATP III (Anon, 2002), and three child-specific definitions adapted by Cook et al. (Cook et al., 2003), Weiss et al. (Weiss et al., 2004), and De Ferranti et al. (de Ferranti et al., 2004).
BP (16.0% to 22.9%). Boys generally had a higher prevalence of all components than girls. However, all these differences were not significant. Table 2 shows the PCA results and three factors in boys (obesity, hypertension, dyslipidemia) cumulatively that explained 64.3%, and four factors in females (obesity, hypertension, dyslipidemia, and hyperglycemia) that accounted for 73.6% of the observed variance of MetS. Obesity, hypertension and dyslipidemia explained 25.5%, 19.6% and 17.4% of the observed variation of MetS, respectively.
Statistical analysis All data were analyzed using STATA 12.0 (StataCorp, 2011) with “svy” commands to adjust for cluster sampling. Gender or BMI status differences in prevalence were examined using the Chi-square test. BMI, WC, SBP, DBP, triglycerides (TG), High Density Lipoprotein cholesterol (HDL-c), and Low Density Lipoprotein cholesterol (LDL-c) were all entered into the principal component analysis (PCA) using the first principal component to account for the largest amount of variance in the sample. We used an eigenvalue ≥ 1 as the criteria for determining the number of components to retain. The principal components (factors) retained were rotated using orthogonal Varimax method to facilitate their interpretation. Variables that had factor loadings ≥ 0.4 (or ≤− 0.4) were considered as major constituents of this factor.
Discussion The prevalence of MetS among adolescents in Ho Chi Minh City was high but differed, depending on the definition used. When the IDF, Cook and the De Ferranti definitions were applied, we found that the prevalence of MetS was higher in Vietnamese adolescents than that reported for adolescents in Hong Kong (Kong et al., 2008), South Korea (Park et al., 2009), China (Li et al., 2008; Yi-Qun and Cheng-Ye, 2008), and India (Singh et al., 2007). The high prevalence of MetS among adolescents in our study may be because the sample investigated came from a setting where there have been rapid changes in socio-economic status and lifestyles which resulted in increases of overweight/obesity and decreases of physical activity (Hong et al., 2007; Trang et al., 2012), while national samples were used in other Asian studies (which included both urban and rural populations). The factor analysis showed that obesity could explain the highest proportion of metabolic components confirming the strong association between obesity factor and MetS and the important role of this factor in MetS, as consistently seen in other studies (Ghosh, 2007; Ng et al., 2007). However, high TG, BP and low HDL-c were found as the most prevalent variables instead of obesity suggesting that each risk factor might have different weights on the contributions to the MetS. The prevalence of MetS in boys was not higher than the prevalence in girls for all definitions. This might be explained by the higher percentage of some components of MetS in girls, such as percentage with high TG and high BP, though the prevalence of overweight/obesity in boys was higher than in girls. Though the
Results There were 617 out of 693 participants having blood tests (response rate 89%). The mean age of the sampled subjects was 13.9 years (± 0.7). Overall 15.5% of the students were overweight/ obese, with a marked difference by gender (20.5% in boys and 11.4% in girls) (p = 0.01). Table 1 showed that the prevalence of MetS defined by the IDF, ATP III, Cook's, Weiss's, and De Ferranti's was 4.6%, 3.9%, 6.3%, 6.6%, and 12.5%, respectively. The prevalence of MetS was the lowest when applying the criteria of ATP III, and was the highest when applying De Ferranti's definition. The prevalence of MetS among adolescents who were overweight and obese was significantly higher than that of adolescents with normal BMI (p b 0.001). In all definitions, impaired fasting glucose was the least common. The most common individual component of MetS was high TG level (11.2% to 42.0%), followed by low HDL-c (11.5% to 36.1%), and high
Table 1 Prevalence of metabolic syndrome by gender and by BMI status and prevalence of different components of metabolic syndrome by different definitions among adolescents 13 to 16 years old of Ho Chi Minh City in 2007.
Gender Boys (n = 284) Girls (n = 333) Total (n = 617) BMI statusf Normal (n = 511) Overweight/obese (n = 106) Components of metabolic syndrome Central obesity Elevated BP Impaired fasting glucose Low HDL-c High TG level
IDF (Zimmet et al., 2007b)a
ATPIII (Anon, 2002)b
Cook et al. (2003)c
Weiss et al. (2004)d
de Ferranti et al. (2004)e
%
%
%
%
%
95% CI
95% CI
95% CI
95% CI
95% CI
4.6 4.7 4.6
2.5 2.1 2.9
6.6 7.2 6.3
2.1 4.5 3.9
0.4 2.8 2.4
3.8 6.2 5.4
6.4 6.3 6.3
3.4 4.3 4.3
9.3 8.3 8.3
4.9 8.1 6.6
2.4 6.0 4.7
7.5 10.2 8.6
13.0 12.0 12.5
9.5 9.5 10.0
16.6 14.5 15.0
2.0 9.9
0.8 4.6
3.1 15.2
2.2 10.0
1.3 4.0
3.1 15.8
4.2 14.9
2.4 3.0
5.9 26.7
5.8 8.9
4.0 3.4
7.6 14.5
8.2 26.7
6.0 15.3
10.3 38.1
10.1 24.8 5.1 11.5 11.2
7.5 20.4 1.4 7.9 8.0
13.3 29.3 8.8 15.2 14.4
1.5 22.0 1.0 36.1 11.7
0.5 18.8 0.2 32.2 9.1
2.4 25.3 1.7 39.9 14.2
10.1 22.9 1.0 11.5 32.4
7.5 19.5 0.2 7.9 28.7
13.3 26.2 1.7 15.2 36.1
N/A 16.0 0.0 11.5 32.4
13.1
18.9
7.9 28.7
15.2 36.1
17.8 22.9 2.6 36.1 42.0
14.8 19.5 0.1 32.2 38.1
20.9 26.2 6.2 39.9 45.9
a IDF (International Diabetes Federation) definition for children aged 10–16: having WC ≥90th percentile, and two or more of the following criteria: TG ≥ 1.7 mmol/l (150 mg/dl), HDL-c b 1.03 mmol/l (40 mg/dl), BP: Systolic ≥ 130 mm Hg or diastolic ≥ 85 mm Hg, fasting glucose ≥ 5.6 mmol/l (100 mg/dl). b ATP (Adult Treatment Panel) definition: having three or more of the following criteria: WC> 102 cm (male), >88 cm (female), TG ≥1.65 mmol/l (150 mg/dl), HDL-c b 1.03 mmol/l (40 mg/dl) for male or b1.3 mmol/l (50 mg/dl) for female, BP: systolic ≥130 mm Hg or diastolic ≥ 85 mm Hg, fasting glucose ≥6.1 mmol/l (110 mg/dl). c Cook's definition: having three or more of the following criteria: WC≥ 90th percentile value for age and sex, TG ≥1.24 mmol/l (110 mg/dl), HDL-c b 1.03 mmol/l (40 mg/dl), BP: ≥90th for age, sex and height, fasting glucose ≥ 6.1 mmol/l (110 mg/dl). d Weiss' definition: having three or more of the following criteria: BMI ≥97th percentile for US adolescents (BMI z-score ≥ 2.0), TG > 95th percentile, HDL-c b 5th percentile, BP: ≥95th for age and sex, IGT (impaired glucose tolerance: test glucose 2 h)≥ 140 mg/dl (7.8 mmol/l) and ≤200 (11.1 mmol/l). e de Ferranti' definition: having three or more of the following criteria: WC>75th percentile value for age and sex, TG≥1.1 mmol/l (100 mg/dl), HDL-cb 1.3 mmol/l (40 mg/dl), except in boys aged 15 to 19 years b1.17 mmol/l (45 mg/dl), BP: >90th for age, sex and height, fasting glucose≥6.1 mmol/l (110 mg/dl). f Defined using IOTF (International Obesity Task Force) BMI cut-offs.
T.K. Hong et al. / Preventive Medicine 55 (2012) 409–411
411
Table 2 Results of principal components analysis with Varimax rotation of adolescents 13 to 16 years old of Ho Chi Minh City in 2007. Total factors
Boys factors
1 BMI (kg/m2) WC (cm) Systolic BP (mm Hg) Diastolic BP (mm Hg) Triglycerides (mmol/L) HDL-c (mmol/L) LDL-c (mmol/L) Fasting glucose (mmol/L) % variance explained Cumulative variance a
2 a
0.915 0.884a 0.303 0.112 0.096 −0.144 −0.105 −0.195 0.255 0.255
0.163 0.204 0.818a 0.859a 0.101 0.025 0.498a 0.300 0.198 0.453
3 0.044 0.116 0.060 0.023 0.794a −0.762a 0.187 0.354 0.174 0.627
Girls factors
1
2 a
0.906 0.899a 0.332 0.122 0.101 −0.214 −0.007 −0.350 0.275 0.275
0.196 0.203 0.806a 0.851a 0.153 0.037 0.516a 0.248 0.193 0.467
3 0.081 0.117 0.029 0.079 0.776a −0.733a 0.336 0.354 0.176 0.643
1 a
0.917 0.910a 0.203 0.036 −0.013 −0.063 −0.061 −0.088 0.236 0.236
2
3
4
0.135 0.087 0.865a 0.885a 0.085 0.084 0.411a 0.083 0.198 0.434
0.017 0.021 0.034 −0.032 0.812a −0.816a 0.089 0.015 0.167 0.601
−0.010 −0.003 −0.019 0.091 0.131 0.076 0.555a 0.860a 0.135 0.736
Factor loading (in bold) ≤−0.4 or ≥0.4.
prevalence of MetS varied according to criteria used, it is not possible to identify a specific definition for Vietnamese adolescents. However, in future studies in Vietnam we would recommend the application of a commonly used definition specified for children and adolescents— i.e. the IDF definition (Zimmet et al., 2007b)—to ensure that valid comparisons can be made over time in Vietnam and between countries. The key strength of our study included the data collection with valid and reliable methods and tools conducted on a representative study sample. Our findings should be, however, interpreted keeping in mind some limitations: Data was collected in urban areas of Ho Chi Minh City, a population with higher socio-economic status and higher prevalence of obesity than the general populations from other regions of the country. Thus, the prevalence of MetS estimated from this study may not represent the situation for Vietnamese adolescents across the country. Conclusions The prevalence of MetS in urban Vietnamese adolescents was high, especially among overweight/obese adolescents, which indicates a significant health issue running in parallel with the increase of overweight/obese adolescents. Obesity is a powerful correlate of cardiovascular risk in Vietnamese adolescents. Authors contribution TKH conducted data analysis and prepared the manuscript. NHHDT was responsible for the management of data collection and entry and contributed in part to the data analysis and preparing the manuscript. MJD contributed to the analysis of data and preparation of the manuscript. No author has any financial or personal relationships with the organization sponsoring this research. The corresponding author has full access to all the data in the study and had final responsibility for the decision to submit for publication. Conflict of interest statement The authors declare that there are no conflicts of interests.
Acknowledgments Data collection was conducted with a grant from the Nestlé Foundation, Switzerland. We would like to say thanks to Dr. Ho Thi Kim Lien, Department of Community Health, Pham Ngoc Thach University of Medicine, Dr. Phan Nguyen Thanh Binh and Dr. Nguyen Hong Vu, Nutrition Center of Ho Chi Minh City, and all data collectors for their enormous help in data collection, entry and cleaning. Nguyen
HHD Trang received a partial PhD scholarship from the University of Sydney World Scholars and Hoc Mai Foundation, the University of Sydney. References Anon, 2002. Third report of the National Cholesterol Education Program (NCEP) expert panel on detection, evaluation, and treatment of high blood cholesterol in adults (Adult Treatment Panel III) final report. Circulation 106, 3143–3421. Christofaro, D.G.D., Fernandes, R.A., Gerage, A.M., Alves, M.J., Polito, M.D., ARd, Oliveira, 2009. Validação do monitor de medida de pressão arterial Omron HEM 742 em adolescentes. Arq. Bras. Cardiol. 92, 10–15. Cole, T.J., Bellizzi, M.C., Flegal, K.M., Dietz, W.H., 2000. Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ 320, 1240–1243. Cook, S., Weitzman, M., Auinger, P., Nguyen, M., Dietz, W.H., 2003. Prevalence of a metabolic syndrome phenotype in adolescents: findings from the third National Health and Nutrition Examination Survey, 1988–1994. Arch. Pediatr. Adolesc. Med. 157, 821–827. Cruz, M.L., Goran, M.I., 2004. The metabolic syndrome in children and adolescents. Curr. Diab. Rep. 4, 53–62. de Ferranti, S.D., Gauvreau, K., Ludwig, D.S., Neufeld, E.J., Newburger, J.W., Rifai, N., 2004. Prevalence of the metabolic syndrome in American adolescents—findings from the Third National Health and Nutrition Examination Survey. Circulation 110, 2494–2497. Ghosh, A., 2007. Factor analysis of risk variables associated with metabolic syndrome in Asian Indian adolescents. Am. J. Hum. Biol. 19, 34–40. Hong, T.K., Dibley, M.J., Sibbritt, D., Binh, P.N., Trang, N.H., Hanh, T.T., 2007. Overweight and obesity are rapidly emerging among adolescents in Ho Chi Minh City, Vietnam, 2002–2004. Int. J. Pediatr. Obes. 2, 194–201. Kong, A.P., Ko, G.T., Ozaki, R., Wong, G.W., Tong, P.C., Chan, J.C., 2008. Metabolic syndrome by the new IDF criteria in Hong Kong Chinese adolescents and its prediction by using body mass index. Acta Paediatr. 97, 1738–1742. Li, Y., Yang, X., Zhai, F., et al., 2008. Prevalence of the metabolic syndrome in Chinese adolescents. Br. J. Nutr. 99, 565–570. Ng, V.W.S., Kong, A.P.S., Choi, K.C., et al., 2007. BMI and waist circumference in predicting cardiovascular risk factor clustering in Chinese adolescents. Obesity 15, 494–503. Park, M.J., Boston, B.A., Oh, M., Jee, S.H., 2009. Prevalence and trends of metabolic syndrome among Korean adolescents: from the Korean NHANES Survey, 1998–2005. J. Pediatr. 155, 529–534. Pickering TG, Hall JE, Appel LJ, et al., “Recommendations for blood pressure measurement in humans and experimental animals.” Hypertension 45: 142–161 Singh, R., Bhansali, A., Sialy, R., Aggarwal, A., 2007. Prevalence of metabolic syndrome in adolescents from a north Indian population. Diabet. Med. 24, 195–199. Trang, N.H., Hong, T.K., Dibley, M.J., 2012. Cohort profile: Ho Chi Minh City youth cohort— changes in diet, physical activity, sedentary behaviour and relationship with overweight/obesity in adolescents. BMJ Open 2, e000362. Weiss, R., Dziura, J., Burgert, T.S., et al., 2004. Obesity and the metabolic syndrome in children and adolescents. N. Engl. J. Med. 350, 2362–2374. Yi-Qun, X.U., Cheng-Ye, J.I., 2008. Prevalence of the metabolic syndrome in secondary school adolescents in Beijing, China. Acta Pediatr. 97, 348–353. Yusuf, S., Reddy, S., Ounpuu, S., Anand, S., 2001. Global burden of cardiovascular diseases: Part II: variations in cardiovascular disease by specific ethnic groups and geographic regions and prevention strategies. Circulation 104, 2855–2864. Zimmet, P., Alberti, G., Kaufman, F., et al., 2007a. The metabolic syndrome in children and adolescents. Lancet 369, 2059–2061. Zimmet, P., Alberti, K.G., Kaufman, F., et al., 2007b. The metabolic syndrome in children and adolescents—an IDF consensus report. Pediatr. Diabetes 8, 299–306.
Contents lists available at SciVerse ScienceDirect
Preventive Medicine journal homepage: www.elsevier.com/locate/ypmed
Brief Original Report
Prevalence of metabolic syndrome and factor analysis of cardiovascular risk clustering among adolescents in Ho Chi Minh City, Vietnam Tang Kim Hong a,⁎, Nguyen Hoang Hanh Doan Trang a, b,⁎, Michael J. Dibley b a b
Department of Community Health, Pham Ngoc Thach University of Medicine, Ho Chi Minh City, Viet Nam Sydney School of Public Health, Sydney Medical School, University of Sydney, NSW 2006 Australia
a r t i c l e
i n f o
Available online 10 September 2012 Keywords: Metabolic syndrome Cardiovascular risk factors Adolescents
a b s t r a c t Objective. This study aimed to describe the prevalence of metabolic syndrome (MetS) in adolescents of Ho Chi Minh City (HCMC) and to identify components of cardiovascular risk clusters. Methods. A cross-sectional study was conducted on a representative sample of 693 high-school students 13 to 16 years old in 2007. MetS was defined according to five different definitions: the Pediatric International Diabetes Federation, the Adult Treatment Panel III, and the modified definitions by Cook, Weiss, and De Ferranti. Principal components analysis (PCA) was carried out to cluster risk factors. Results. The prevalence of MetS was high and varied from 3.9% to 12.5%, depending on the criteria used. High levels of triglycerides (or low High Density Lipoprotein Cholesterol) and high blood pressure were the most prevalent components of MetS, while impaired glucose tolerance was the least prevalent. PCA showed three factors in boys (obesity, hypertension, dyslipidemia) that cumulatively explained 64.3%, and four factors in females (obesity, hypertension, dyslipidemia, and hyperglycemia) that accounted for 73.6% of the observed variance of MetS. Conclusions. The prevalence of MetS in HCMC adolescents was high. Obesity accounts for the maximum variance in clustering and appears to be a more powerful correlate of cardiovascular risk than other variables. © 2012 Elsevier Inc. All rights reserved.
Introduction Metabolic syndrome (MetS) is rapidly increasing worldwide in children and adolescents, in-line with rising childhood obesity and a sedentary life style (Cruz and Goran, 2004; Weiss et al., 2004). It is becoming a growing public health issue (Zimmet et al., 2007a), especially in developing countries, where the prevalence of chronic diseases is rising far more rapidly in comparison to developed nations (Yusuf et al., 2001). In Vietnam, adolescent obesity is emerging as an important health problem (Hong et al., 2007); however, there is no report of MetS in adolescents. A unified definition of MetS for adolescents is lacking. Different cut-offs including the National Cholesterol Education Program Adult Treatment Panel III (ATP III) criteria (Anon, 2002) adapted by Cook et al. (Cook et al., 2003), by Weiss et al. (Weiss et al., 2004), by De Ferranti et al. (de Ferranti et al., 2004), and the Pediatric International Diabetes Federation (IDF) (Zimmet et al., 2007b) have been used to assess MetS prevalence in adolescents (Kong et al., 2008; Park et al., 2009; Singh et al., 2007). This study was undertaken to describe the prevalence of MetS and identify the clustering of components of risk
⁎ Corresponding authors at: Pham Ngoc Thach University of Medicine, 86/2 Thanh Thai Street, District 10, Ho Chi Minh City, Viet Nam. Fax: +84 8 9574 474. E-mail address: [email protected] (T.K. Hong). 0091-7435/$ – see front matter © 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ypmed.2012.09.002
variables associated with MetS in an urban population of Vietnamese adolescents from Ho Chi Minh City. Methods A cross-sectional assessment was conducted in 2007 on urban highschool students of Ho Chi Minh City. This sample was recruited for a cohort study started in 2004 (Trang et al., 2012). The study was approved by the ethics committee of Pham Ngoc Thach University of Medicine. Written consent was obtained from both students and their parents prior to data collection. Weight was measured without shoes and heavy clothes, using a Tanita electronic scale and was recorded to the nearest 0.1 kg. Standing height was taken with a suspended Microtoise tape to the nearest 0.1 cm. Waist circumference (WC) was measured to the nearest 0.5 cm with a non-elastic tape applied at a point midway between the lower border of the rib cage and the iliac crest. Fasting blood samples of 5 ml were taken in the morning at the subject's school by a trained laboratory technician. On the previous day, the students were instructed to fast for 12 h before the test. Blood specimens were kept in ice at 0 °C before being transported back to the Laboratory of the Diagnostic Center of Ho Chi Minh City for further processing. Serum lipid and glucose concentrations were measured and read on a BM/Hitachi 917 analyzer (Roche Diagnostics, IN, USA). Systolic and diastolic blood pressures (BP) were measured with an Omron BP monitor after 15 min of rest. This kind of device has been validated for BP measurement in adolescents (Christofaro et al., 2009) and the cuff used was recommended by the American Heart Association (Pickering et al.).
410
T.K. Hong et al. / Preventive Medicine 55 (2012) 409–411
The subjects were classified as overweight/obese by applying the age- and sex‐specific International Obesity Task Force (IOTF) BMI cut-offs (Cole et al., 2000), and classified as having MetS according to five different definitions: the Pediatric IDF (Zimmet et al., 2007b), ATP III (Anon, 2002), and three child-specific definitions adapted by Cook et al. (Cook et al., 2003), Weiss et al. (Weiss et al., 2004), and De Ferranti et al. (de Ferranti et al., 2004).
BP (16.0% to 22.9%). Boys generally had a higher prevalence of all components than girls. However, all these differences were not significant. Table 2 shows the PCA results and three factors in boys (obesity, hypertension, dyslipidemia) cumulatively that explained 64.3%, and four factors in females (obesity, hypertension, dyslipidemia, and hyperglycemia) that accounted for 73.6% of the observed variance of MetS. Obesity, hypertension and dyslipidemia explained 25.5%, 19.6% and 17.4% of the observed variation of MetS, respectively.
Statistical analysis All data were analyzed using STATA 12.0 (StataCorp, 2011) with “svy” commands to adjust for cluster sampling. Gender or BMI status differences in prevalence were examined using the Chi-square test. BMI, WC, SBP, DBP, triglycerides (TG), High Density Lipoprotein cholesterol (HDL-c), and Low Density Lipoprotein cholesterol (LDL-c) were all entered into the principal component analysis (PCA) using the first principal component to account for the largest amount of variance in the sample. We used an eigenvalue ≥ 1 as the criteria for determining the number of components to retain. The principal components (factors) retained were rotated using orthogonal Varimax method to facilitate their interpretation. Variables that had factor loadings ≥ 0.4 (or ≤− 0.4) were considered as major constituents of this factor.
Discussion The prevalence of MetS among adolescents in Ho Chi Minh City was high but differed, depending on the definition used. When the IDF, Cook and the De Ferranti definitions were applied, we found that the prevalence of MetS was higher in Vietnamese adolescents than that reported for adolescents in Hong Kong (Kong et al., 2008), South Korea (Park et al., 2009), China (Li et al., 2008; Yi-Qun and Cheng-Ye, 2008), and India (Singh et al., 2007). The high prevalence of MetS among adolescents in our study may be because the sample investigated came from a setting where there have been rapid changes in socio-economic status and lifestyles which resulted in increases of overweight/obesity and decreases of physical activity (Hong et al., 2007; Trang et al., 2012), while national samples were used in other Asian studies (which included both urban and rural populations). The factor analysis showed that obesity could explain the highest proportion of metabolic components confirming the strong association between obesity factor and MetS and the important role of this factor in MetS, as consistently seen in other studies (Ghosh, 2007; Ng et al., 2007). However, high TG, BP and low HDL-c were found as the most prevalent variables instead of obesity suggesting that each risk factor might have different weights on the contributions to the MetS. The prevalence of MetS in boys was not higher than the prevalence in girls for all definitions. This might be explained by the higher percentage of some components of MetS in girls, such as percentage with high TG and high BP, though the prevalence of overweight/obesity in boys was higher than in girls. Though the
Results There were 617 out of 693 participants having blood tests (response rate 89%). The mean age of the sampled subjects was 13.9 years (± 0.7). Overall 15.5% of the students were overweight/ obese, with a marked difference by gender (20.5% in boys and 11.4% in girls) (p = 0.01). Table 1 showed that the prevalence of MetS defined by the IDF, ATP III, Cook's, Weiss's, and De Ferranti's was 4.6%, 3.9%, 6.3%, 6.6%, and 12.5%, respectively. The prevalence of MetS was the lowest when applying the criteria of ATP III, and was the highest when applying De Ferranti's definition. The prevalence of MetS among adolescents who were overweight and obese was significantly higher than that of adolescents with normal BMI (p b 0.001). In all definitions, impaired fasting glucose was the least common. The most common individual component of MetS was high TG level (11.2% to 42.0%), followed by low HDL-c (11.5% to 36.1%), and high
Table 1 Prevalence of metabolic syndrome by gender and by BMI status and prevalence of different components of metabolic syndrome by different definitions among adolescents 13 to 16 years old of Ho Chi Minh City in 2007.
Gender Boys (n = 284) Girls (n = 333) Total (n = 617) BMI statusf Normal (n = 511) Overweight/obese (n = 106) Components of metabolic syndrome Central obesity Elevated BP Impaired fasting glucose Low HDL-c High TG level
IDF (Zimmet et al., 2007b)a
ATPIII (Anon, 2002)b
Cook et al. (2003)c
Weiss et al. (2004)d
de Ferranti et al. (2004)e
%
%
%
%
%
95% CI
95% CI
95% CI
95% CI
95% CI
4.6 4.7 4.6
2.5 2.1 2.9
6.6 7.2 6.3
2.1 4.5 3.9
0.4 2.8 2.4
3.8 6.2 5.4
6.4 6.3 6.3
3.4 4.3 4.3
9.3 8.3 8.3
4.9 8.1 6.6
2.4 6.0 4.7
7.5 10.2 8.6
13.0 12.0 12.5
9.5 9.5 10.0
16.6 14.5 15.0
2.0 9.9
0.8 4.6
3.1 15.2
2.2 10.0
1.3 4.0
3.1 15.8
4.2 14.9
2.4 3.0
5.9 26.7
5.8 8.9
4.0 3.4
7.6 14.5
8.2 26.7
6.0 15.3
10.3 38.1
10.1 24.8 5.1 11.5 11.2
7.5 20.4 1.4 7.9 8.0
13.3 29.3 8.8 15.2 14.4
1.5 22.0 1.0 36.1 11.7
0.5 18.8 0.2 32.2 9.1
2.4 25.3 1.7 39.9 14.2
10.1 22.9 1.0 11.5 32.4
7.5 19.5 0.2 7.9 28.7
13.3 26.2 1.7 15.2 36.1
N/A 16.0 0.0 11.5 32.4
13.1
18.9
7.9 28.7
15.2 36.1
17.8 22.9 2.6 36.1 42.0
14.8 19.5 0.1 32.2 38.1
20.9 26.2 6.2 39.9 45.9
a IDF (International Diabetes Federation) definition for children aged 10–16: having WC ≥90th percentile, and two or more of the following criteria: TG ≥ 1.7 mmol/l (150 mg/dl), HDL-c b 1.03 mmol/l (40 mg/dl), BP: Systolic ≥ 130 mm Hg or diastolic ≥ 85 mm Hg, fasting glucose ≥ 5.6 mmol/l (100 mg/dl). b ATP (Adult Treatment Panel) definition: having three or more of the following criteria: WC> 102 cm (male), >88 cm (female), TG ≥1.65 mmol/l (150 mg/dl), HDL-c b 1.03 mmol/l (40 mg/dl) for male or b1.3 mmol/l (50 mg/dl) for female, BP: systolic ≥130 mm Hg or diastolic ≥ 85 mm Hg, fasting glucose ≥6.1 mmol/l (110 mg/dl). c Cook's definition: having three or more of the following criteria: WC≥ 90th percentile value for age and sex, TG ≥1.24 mmol/l (110 mg/dl), HDL-c b 1.03 mmol/l (40 mg/dl), BP: ≥90th for age, sex and height, fasting glucose ≥ 6.1 mmol/l (110 mg/dl). d Weiss' definition: having three or more of the following criteria: BMI ≥97th percentile for US adolescents (BMI z-score ≥ 2.0), TG > 95th percentile, HDL-c b 5th percentile, BP: ≥95th for age and sex, IGT (impaired glucose tolerance: test glucose 2 h)≥ 140 mg/dl (7.8 mmol/l) and ≤200 (11.1 mmol/l). e de Ferranti' definition: having three or more of the following criteria: WC>75th percentile value for age and sex, TG≥1.1 mmol/l (100 mg/dl), HDL-cb 1.3 mmol/l (40 mg/dl), except in boys aged 15 to 19 years b1.17 mmol/l (45 mg/dl), BP: >90th for age, sex and height, fasting glucose≥6.1 mmol/l (110 mg/dl). f Defined using IOTF (International Obesity Task Force) BMI cut-offs.
T.K. Hong et al. / Preventive Medicine 55 (2012) 409–411
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Table 2 Results of principal components analysis with Varimax rotation of adolescents 13 to 16 years old of Ho Chi Minh City in 2007. Total factors
Boys factors
1 BMI (kg/m2) WC (cm) Systolic BP (mm Hg) Diastolic BP (mm Hg) Triglycerides (mmol/L) HDL-c (mmol/L) LDL-c (mmol/L) Fasting glucose (mmol/L) % variance explained Cumulative variance a
2 a
0.915 0.884a 0.303 0.112 0.096 −0.144 −0.105 −0.195 0.255 0.255
0.163 0.204 0.818a 0.859a 0.101 0.025 0.498a 0.300 0.198 0.453
3 0.044 0.116 0.060 0.023 0.794a −0.762a 0.187 0.354 0.174 0.627
Girls factors
1
2 a
0.906 0.899a 0.332 0.122 0.101 −0.214 −0.007 −0.350 0.275 0.275
0.196 0.203 0.806a 0.851a 0.153 0.037 0.516a 0.248 0.193 0.467
3 0.081 0.117 0.029 0.079 0.776a −0.733a 0.336 0.354 0.176 0.643
1 a
0.917 0.910a 0.203 0.036 −0.013 −0.063 −0.061 −0.088 0.236 0.236
2
3
4
0.135 0.087 0.865a 0.885a 0.085 0.084 0.411a 0.083 0.198 0.434
0.017 0.021 0.034 −0.032 0.812a −0.816a 0.089 0.015 0.167 0.601
−0.010 −0.003 −0.019 0.091 0.131 0.076 0.555a 0.860a 0.135 0.736
Factor loading (in bold) ≤−0.4 or ≥0.4.
prevalence of MetS varied according to criteria used, it is not possible to identify a specific definition for Vietnamese adolescents. However, in future studies in Vietnam we would recommend the application of a commonly used definition specified for children and adolescents— i.e. the IDF definition (Zimmet et al., 2007b)—to ensure that valid comparisons can be made over time in Vietnam and between countries. The key strength of our study included the data collection with valid and reliable methods and tools conducted on a representative study sample. Our findings should be, however, interpreted keeping in mind some limitations: Data was collected in urban areas of Ho Chi Minh City, a population with higher socio-economic status and higher prevalence of obesity than the general populations from other regions of the country. Thus, the prevalence of MetS estimated from this study may not represent the situation for Vietnamese adolescents across the country. Conclusions The prevalence of MetS in urban Vietnamese adolescents was high, especially among overweight/obese adolescents, which indicates a significant health issue running in parallel with the increase of overweight/obese adolescents. Obesity is a powerful correlate of cardiovascular risk in Vietnamese adolescents. Authors contribution TKH conducted data analysis and prepared the manuscript. NHHDT was responsible for the management of data collection and entry and contributed in part to the data analysis and preparing the manuscript. MJD contributed to the analysis of data and preparation of the manuscript. No author has any financial or personal relationships with the organization sponsoring this research. The corresponding author has full access to all the data in the study and had final responsibility for the decision to submit for publication. Conflict of interest statement The authors declare that there are no conflicts of interests.
Acknowledgments Data collection was conducted with a grant from the Nestlé Foundation, Switzerland. We would like to say thanks to Dr. Ho Thi Kim Lien, Department of Community Health, Pham Ngoc Thach University of Medicine, Dr. Phan Nguyen Thanh Binh and Dr. Nguyen Hong Vu, Nutrition Center of Ho Chi Minh City, and all data collectors for their enormous help in data collection, entry and cleaning. Nguyen
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