O r i g i n a l
P a p e r
Metabolic Syndrome Risk Factors Among a Sample of Overweight and Obese Mexican Children Leticia Elizondo-Montemayor, MD;1 Mo´nica Serrano-Gonza´lez, MD;1 Patricia A. Ugalde-Casas, MD;1 Carlos Cuello-Garcı´a, MD;2 Jose´ R. Borbolla-Escoboza, MD3
The objective of this study was to estimate the prevalence and correlations of components of the metabolic syndrome (MetS) using the International Diabetes Federation (IDF) pediatric definition in a cross-sectional study of 215 overweight ⁄ obese Mexican children aged 6 to 12. There are no previous studies of this kind in Mexican children. Clinical, anthropometric, and laboratory measurements were performed. The prevalence of MetS using the pediatric IDF criteria was 6.7% (95% confidence interval, 4.0–11.1). A higher proportion of children in the younger age group had waist circumference above the cutoff, while a higher proportion in the older age group had hyperglycemia. Children with MetS had higher percentages of body fat, body mass index, total cholesterol, and low-density lipoprotein cholesterol. Increased triglycerides, decreased high-density lipoprotein cholesterol, and waist circumference were most highly associated with MetS. This has significant From the Clinical Research Centre;1 the EvidenceBased Medicine Department;2 and the Research and Innovation Centre,3 Instituto Tecnolo´gico y de Estudios Superiores de Monterrey, School of Medicine, Monterrey, Mexico Address for correspondence: Leticia Elizondo-Montemayor, MD, Av. Morones Prieto 3000 Poniente, Colonia los Doctores, 64710 Monterrey, Nuevo Leo´n, Mexico E-mail:
[email protected] Manuscript received November 11, 2009; revised December 14, 2009; accepted December 23, 2009
doi: 10.1111/j.1751-7176.2010.00263.x
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implications for public health. J Clin Hypertens (Greenwich).2010;12:380–387. ª2010 Wiley Periodicals, Inc.
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besity in children is a rapidly expanding disease across the world1,2; it is also an emerging public health problem in Mexico, where its prevalence has increased. Data from the Mexican National Nutrition Survey showed that 26.1% of school-aged children are overweight or obese.3 Childhood obesity increases the risk of developing cardiovascular disease, diabetes, hypertension, dyslipidemia, sleep apnea, osteoarthritis, cancer, and psychological disturbances, among others,1,4 and can eventually lead to the metabolic syndrome (MetS). Both cross-sectional and prospective studies in children have linked MetS, or clusters of factors considered to be part of it, to diabetes,5,6 cardiovascular disease,7,8 and hepatosteatosis,9 among other complications. Few studies have estimated the prevalence of MetS in children and adolescents; reports vary greatly among countries, from 4.2% to 18% and among obese children from 19.5% to 59%10–16 not only because of the characteristics of the studied populations, but mainly because of the different definitions that were used.10–12,15–22 Until recently, no standard definition of MetS was available for use in pediatric populations. Consequently, researchers have used an assortment of definitions. In 2007, the International Diabetes Federation (IDF) presented a definition for use in children and adolescents,14 however, to this date, we have found
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only one study using this definition to address the syndrome’s prevalence.13 In Mexico, very few studies have addressed the issue of the prevalence of MetS, each used different clusters of criteria and cutoff values and they reported a prevalence that ranged from 4.8% to 26.1%.12,21,22 There are no studies from Mexico using the pediatric IDF definition. From a clinical and public health perspective, the recognition of MetS in overweight and obese children who have not yet developed a metabolic and ⁄ or cardiovascular disease is of great importance. This is especially important for children aged 6 to 9, since the IDF consensus does not include this age group, nor is there any standard definition for them, but they do have a high prevalence of overweight and obesity. Thus, we conducted this study to estimate the prevalence of MetS in children aged 6 to 12 with the pediatric IDF definition. The use of a single unified definition will make it possible to estimate the global pediatric prevalence of MetS, making valid comparisons between countries and addressing strategies for adequate interventions. MATERIALS AND METHODS Study Population We studied a cross-sectional sample of 215 overweight and obese school-aged children from 8 urban and suburban public schools distributed in the metropolitan area of the city of Monterrey, in northern Mexico. Forty-four children from the same schools with normal range body mass index (BMI) (below the 85th percentile for age and gender) were studied as controls. Participants were ethnically homogeneous (all of them were Mexican-Hispanic). Inclusion criteria were as follows: attendance at one of the participant schools from the first to the sixth grade; age 6 to 12; BMI 85th percentile for age and sex; 12-hour overnight fast; and signed informed consent from both parents ⁄ caretakers and children. The use of drugs for high blood pressure, hyperglycemia, or dyslipidemia was considered an exclusion criterion. Approvals by the Ethics and the Research Committees of the School of Medicine Tecnolo´gico de Monterrey and by the State Education Authorities were obtained, as well as written informed consent from parents and children. In accordance with the IDF criteria for MetS, participants were divided into 2 age groups: (1) children aged 6 to 9 and (2) children aged 10 to 12. Clinical Evaluation Parents responded to a questionnaire that asked about familial risk factors: diabetes, myocardial
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infarction, cerebrovascular event, hypertension, and dyslipidemia. Anthropometric assessment was performed in all participants (n=259) within each school. We measured height, weight, waist circumference (WC), and percentage of body fat (% BF) by bioimpedance, according to standardized methods. BMI was calculated as weight (kg) divided by the square of height (m). Each anthropometric measure was performed by the same trained examiner in all children to control for interobserver variability. Blood pressure was measured in every participant by the same physician, using an aneroid sphygmomanometer (Welch Allyn, Skaneateles, NY) with an appropriate cuff according to the participant’s size and following the standardized technique described by the American Heart Association; 2 measurements were obtained while the participants were calm and seated, and the average was calculated. Tanner stage was self-evaluated by means of schematic drawings from which the children selected the most appropriate image. Laboratory Assessment Blood samples were obtained after a 12-hour overnight fast. Samples were kept at 2 to 8C, centrifuged within the first 3 hours and then refrigerated again at 2 to 8C. Serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and glucose were measured by the technique of reflective photometry (Beer-Lambert’s law) using an automated analyzer (Architect c8000; Abbott Laboratories, Abbott Park, IL), with an intra- and inter-assay coefficient of variation below 4.7%. Definitions To define MetS, we used the pediatric criteria established by the IDF in 2007.14 The IDF establishes the diagnosis of the syndrome by the presence of central obesity defined by WC 90th percentile for age and gender and at least 2 of the other 4 parameters (Table I). LDL-C and TC were classified as altered when equal to or greater than 160 and 200 mg ⁄ dL, respectively, according to the reference values for age and gender. Statistical Analysis Data are presented either as an absolute number with its respective percentage, or else as means with their 95% confidence intervals (CI). Distributions of continuous variables were examined for skewness and kurtosis and by means of the Kolmogorov–Smirnov
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Table I. The International Diabetes Federation Definition of the Metabolic Syndrome in Children and Adolescents Parameter Waist circumference
Cutoff 90th percentile for age and sex
At least 2 of the following: SBP, mm Hg DBP, mm Hg Fasting glucose, mg ⁄ dL HDL-C, mg ⁄ dL Triglycerides, mg ⁄ dL
130 85 100
