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Sumario Vol. 42 - Nº 2 Abril - Junio 2013

Prevalence of Metabolic Syndrome as Defined
by the International Diabetes Federation (IDF)
in Adolescentsfrom Salta, Argentina

Susana Judith Gotthelf

Departamento de Investigación Epidemiológica.
Centro Nacional de Investigaciones Nutricionales. Administración Nacional de Laboratorios e Institutos de Salud. ANLIS. Salta, Argentina.
República de Siria 247. Tel: 0387-4311730 Int. 112.
Correo electrónico

The author declares not having a conflict of interest.
 


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SUMMARY

In 2007 a new definition of Metabolic Syndrome (MS) for children and adolescents, arises from the IDF (International Diabetes Federation), giving to the obesity abdominal region, a prevalent role associated with increased risk of cardiovascular disease and type 2diabetes.
Objective: To estimate the prevalence of MS using IDF criteria among adolescent students in the province of Salta (2008-2009).
Methodology: cross-sectional study. Population: 659 adolescentsbetween 16and 20years old, attendingthe last gradeof public and private high schoolsofSalta (Capital), CafayateandJV.Gonzalez. Variables: MS: WC ≥80cm women, men ≥90cm, TG ≥150 mg / dl, HDL: women ≤50mg/dl, men ≤40mg/dl; systolic / diastolic ≥130/85 mmHg, fasting glucose ≥100mg/dl. BMI z score (WHO). Sociodemographic: sex, residence, school, family income. Statisticalanalysis: Chi square, Fisher (proportions). Kolgomorov (normal), Mann-Whitney U, Kruskal Wallis (median). Logistic regression (SPSS 17) p <0.05.
Results: The overall prevalence of MS was 4.1%, 3.1% in women and 5.5% in men; 3.4% and 5.1% in the Capital and the rest of the province; 0.4% in normally nourished, 13.2% overweight and 50% obese individuals. Median TG, glucose and systolic / diastolic were significantly higher in men, the rest of the province and obese,the WC was higher in the Capital, in men and obese individuals. The multivariate regression analysis was associated with overweight / obesity increased odds of MS (0R 77.46) adjusted by sex, residence and family income.
Conclusions: There is a MS prevalence similar to that reported in other studies with variable features into its components by sex, residence and nutritional status.

Key words: Metabolic Syndrome. Prevalence. Adolescents.
Rev Fed Arg Cardiol. 2013; 42(2): 119-126

 


INTRODUCTION
The change in the epidemiological and nutritional profile that is observed nowadays in Latin America, leads to the co-existence of malnutrition, micronutrients deficiencies and obesity with a subsequent increase in the prevalence of chronic diseases, among them those of cardiovascular origin [1,2].

Obesity is increasing in a significant and alarming way in the world and in age groups as children, teenagers, elderly people, and menopausal women [3]. It is early associated to adverse consequences in health, especially if other risk factors are added (hypertension, dyslipidemias, intolerance to glucose, etc.), joining and constituting what is known as Metabolic Syndrome (MS) [4,5]. The syndrome describes a set of factors that generate cardiovascular risks, related to metabolic, vascular, inflammatory, fibrinolytic and coagulation anomalies, and increasingly more data are reported in literature that document the prevalence of it in teenagers with obesity. This has caused alarm because the carriers of MS may potentially develop diabetes (DM) and coronary artery disease, which is becoming a reality, since from all the cases of diabetes in people younger than 20 years, 8% to 45%of them correspond to DM2 cases [6].

The current prevalence of MS is 4-5% in children and adolescents, according to different population studies, and reaches 40% in teenagers with severe obesity [3]. Since there is still no universal definition of MS, the criteria used in the pediatric practice have changed since the adaptation of those corresponding to adults, to the use of reference scores and percentile values according to gender and age.

In year 2007, a new definition arises from the International Diabetes Federation (IDF), in which abdominal obesity is considered as the independent factor that best relates to insulin resistance, a high level of lipids and hypertension; all of them components of the metabolic syndrome. The new definition, therefore, requires the measurement of central obesity plus two of the following additional factors. Elevated triglycerides (TG), reduced HDLc, increase of pressure and glycemia levels in a fasting state [7].

In our province in particular and in Argentina in general, the data on the prevalence in the population of young people is not very well known, but studies show an increasing tendency of risk factors associated to obesity [8,9], and MS in childhood and adolescence, becoming a Public Health problem, which justifies monitoring it.


GENERAL OBJECTIVE
To estimate the prevalence of Metabolic Syndrome and its components in adolescents attending school in the province of Salta, according to the criteria of the International Diabetes Federation (2008-2009).


MATERIALS AND METHODS
Cross-sectional, descriptive study.
Population: males and females with ages ranging from 16 to 20 years, attending the last course of High School in public and private schools in the province of Salta (Capital city, Cafayate, and JV. González), evaluated in the school period (2008-2009).
Exclusion criteria: carriers of known chronic diseases, eating disorders (anorexia, bulimia), pregnant girls, students with <10 hours of fasting, not authorized by parents or tutors, without consent or participation.
Source of data:secondary, obtained from the database of the “Factores de riesgo cardiovascular en adolescentes de la Provincia de Salta” (Cardiovascular Risk Factors in Adolescents of the Province of Salta), made between years 2008-2009, which used simple random probability sampling of public and private schools in the city of Salta, while in the interior of the province all the schools, all public, were evaluated.
Variables: MS: IDF criteria; WC in females ≥80 cm; males ≥90 cm plus two of the following variables present, TG ≥150 mg/dl; HDL: females ≤50 mg/dl, males ≤40 mg/dl; systolic/diastolic pressure ≥130/85 mmHg; basal glycemia ≥100 mg/dl.
Sociodemographic: gender, geographical area of residence (capital/interior), type of school (public/private), family income (low, medium, high).
Nutrition state 16-18 years, Tables of Z-score of BMI according to gender and age (WHO) [10]: malnutrition ≤2 Z-score; normal >2 <+1; overweight ≥+1; obesity ≥+2.
- 19 years: malnutrition <18.5; normal ≥18.5 <25; overweight ≥25 <30; obesity ≥30 (WHO) [11].
Due to the low prevalence of malnutrition, for the analysis it was joined with the category of normalcy.

Measurements
Blood pressure: A digital blood pressure meter Microlife BP 3BTO-A was used, as well as the automatic method of oscillometric measurement (validated by the British and European Societies of Hypertension). Cuff of 13 cm of width for arm circumference of 22-33 cm. An average between pressure measurements with a 15-minute intervalwas made.

A pilot test was made to standardize and determine the variability of intra-observer and inter-observer measurements, by comparison of averages (student’s t-test) and intraclass correlation coefficient.

Anthropometric variables
BMI
Techniques: Cam scales, capacity 150 kg, minimal clothes and no shoes, with the full weight recorded in kg and g.

Height: standing, metallic tape measure in cm and mm;the measurement was recorded in cm and mm [12].
The measurements were standardized to have an error no greater than 100 g in weight and 0.49 cm in size.

Waist circumference (WC)
Flexible tape measure, not extensible, in millimeters. Patient standing, arms relaxed at the sides of the body, measurement in the middle point between the costal ridge and the iliac crest, while exhaling.

Biochemical: HDL; triglycerides (TG) and basal glycemia (BG), with 10 hours of fasting, by venous puncture, method of dry chemistry with processor with capacity of automatic dilution. Model Vitros 250 Johnson. Internal and external calibrations of the PEC (Programa de Control of Calidad [Program for Quality Control] – Fundación Bioquímica Argentina).

Socioeconomic variables
Level of father/mother income: “low” level (income equal or inferior to the total basic basket); “medium” (value of two total baskets); “high” (above the latter). The total basic basket was taken with data from the INDEC for the region. For the final model of regression, they were regrouped into two categories by similarities: low+medium and high.

Statistical analysis: The results are presented in tables and graphs of distribution of frequencies and association, Chi-squared, Fisher’s test. Comparison of averages: Kolgomorov (normalcy), U Mann-Whitney, Kruskal Wallis (medians). Analysis of multivariate regression analysis, estimations of risks were calculated by odds ratio (OR) with CI 95%.
Statistical programs: SPSS 17 (Windows version).

Ethical aspects. The original study from where the data were obtained, had the support by the Committee of Bioethics of the Sociedad Argentina de Pediatría, the Salta branch. At the time, all the parents or tutors of the teenagers that participated, signed a written authorization, besides a signed consent by the students themselves.

The study had no financing from private companies; since it was programmed by the Centro Nacional de Investigaciones Nutricionales of Salta, within the framework of the budget activities by the Administración Nacional de Laboratorios e Institutos de Salud (ANLIS).


RESULTS
A total of 659 students were evaluated; 386 lived in the Capital area (58.6%) and 273 (41.4%) in the interior of the province. From the sample, 58.2% were females (384).

In Table 1, the percentage distribution of MS is observed and of every one of its components according to the variables considered. Altered systolic pressure and HDL levels were the most prevalent.

Table 1. Prevalence of metabolic syndrome and its components in teenagers attending school in the province of Salta. CNIN 2012

Chi-squared. Fisher *p<0.05. MS: metabolic syndrome. WC: waist circumference. HDL: high-density lipoprotein cholesterol. TG: Triglycerides. BG: basal glycemia. SBP/DBP: Systolic blood pressure/diastolic blood pressure.

 

BMI was significantly associated to a greater prevalence of all MS components. Males presented greater percentages of elevated TG, glycemia and pressure, while females presented altered HDL and WC.

The medians of TG, glycemia and blood pressure were significantly higher for the students from the interior, the male gender, and those with overweight or obesity (Table 2). The lower values of HDL were associated to males, living in the interior, attending a public school, low and medium family income and obesity.

Table 2. Average values and SD of components of the Metabolic Syndrome in adolescents attending schools of the province of Salta. CNIN. 2012

WC: Waist circumference. HD: high-density lipoprotein cholesterol. TG: Triglycerides. BG: Basal glycemia. SBP/DBP: Systolic/diastolic blood pressure. Non-parametric tests, U of Mann Whitney, Kruskal-Wallis *p<0.05.

 

From all the students, 36.1% presented a risk factor for MS, 12.7% two, 2.9% three and 1.4% four factors, Table 3. Besides, significant associations between BMI, gender, place of residence and number of factors were identified.

Table 3. Number of components of Metabolic Syndrome in adolescents attending schools of the province of Salta. CNIN. 2012

Chi-squared. Fisher p<0.05.

 

The model of multivariate logistic regression showed that the probability of MS was 77.46 times (p=0.000) for adolescents with overweight/obesity in relation to those with normal nutrition, adjusted according to gender, place of residence and family income (Table 4). The variable type of school, since it presented a correlation to family income and represented only the city of Salta, was not introduced in the model.

Table 4. Model of logistic regression for Metabolic Syndrome. CNIN. 2012

 


DISCUSSION
The presence of MS in young people and its association to the early appearance of chronic diseases in adulthood [13], has been recently studied, emphasizing the significance of investigating the problem in this age group.

Few data exist in our country and the present study shows us the first ones on adolescents attending school from three cities from the province of Salta, in which the prevalence of MS found was 4.1% (3.1% females and 5.5% males) especially associated to the presence of overweight/obesity with an occurrence of such events of 13.8 and 3.9% respectively.

Metabolic syndrome is the expression of a series of anomalies that, seen individually, carry a risk for health, but that jointly are strengthened. There are different diagnostic criteria for it and recently, the definition by the IDF emerged, which uses waist circumference as a significant reference to define it, allowing to apply it in adolescents. WC is one of the best anthropometric indicators of predictive characterfor cardiovascular diseases and different studies allow to infer that the increases that occur according to time will have repercussions in an increase of MS, a tendency that is being observed in many areas of the world [14,15].

Although the presence of cardiovascular risk factors in adolescence is well known, with its association to obesity and insulin resistance being established, the appearance of complete MS at early ages in life has only been investigated since recent years [16].

Thus, in the city of Posadas, Misiones (2005), the frequency of MS was evaluated in a sample of 532 students with ages between 11 and 20 years according to ATP III criteria. Males, the group between 15 and 20 years and those presenting obesity and overweight presented a greater risk, while 4.5% presented MS [17].

In 2010, 943 teenager students were evaluated, with ages between 11 and 14 years, from high schools from the city of Buenos Aires, and the presence of MS (NCEP-ATPIII) was 5.45% in males and 1.63% in females [18].

In Latin America, Brazil, the study carried out in 2003 in 12-19-year-old teenagers from public schools from Rio de Janeiro, showed a prevalence of MS according to the definition by the WHO of 1.1%, by the NCEP/ATP III of 6.0% and by IDF of 1.6% [19]. In adolescents (10-19 y.o.) from the metropolitan area of Monterrey, Mexico (2005-2006), the prevalence of MS according to ATPIII criteria, was 9.4%, with no differences between genders [20], while in Colombia from 2,603 individuals between children and teenagers from 6 to 18 years old, the overall prevalence of metabolic syndrome was 6.1% (in adolescents 6.6% and in children 5.1%) [21]. Finally, the data published in USA on 2,014 participants from 12-17 y.o. in the National Health and Nutrition Examination Survey (1999-2004) display a prevalence of MS (as defined by the IDF) 4.5%, greater in males (6.7%) than in females (2.1%) [22].

The epidemiological tendency determines that metabolic syndrome appears more frequently in older people and those with greater BMI. However, other studies are already relating it with the nutrition state in children and teenagers, and regardless of the extent of the problem, everyone agree on the increase being directly related to BMI; i.e. obese people present this problem the most, and then those with overweight, and last those with normal nutrition, in whom it virtually does not exist.

In the present paper, the prevalence of MS was 0.4% in people with normal nutrition, 13.2% in teenagers with overweight and 50.0% in those with obesity. Besides multivariate analysis showed that the probability of MS was associated only to overweight/obesity with OR of 77.46 (p=0.000), although male gender and the fact of living in towns from the interior of the province presented OR >1 (1.79 and 2.16).

The association between overweight and Metabolic Syndrome is observed in this paper, just as it was shown in other studies, with conclusive results that show the danger entailed by an increase in weight [23,24]. It is estimated that between 50 and 80% of obese teenagers continued being so in their adulthood and that the probability increases progressively as BMI increases in adolescence. Moreover, young people with very high BMI show a risk of dying in adulthood 30 to 40% higher than people with a moderate BMI [25].

Although BMI is not considered a diagnostic criterion to identify metabolic syndrome, its measurement when assessing the nutrition state to prevent and control obesity in childhood and adolescence is a priority in the medical practice. Thus, in a study made in the Centro Nacional de Investigaciones Nutricionales (2004) on children and teenagers controlled due to obesity, the prevalence of MS was 21.3% in the former and 27.6% in the latter [26]. And in a recent work, in which 1,009 adolescents were evaluated in seven Argentine provinces, and where the prevalence of MS in those with overweight/obesity was 40.3% and 0% in those with normal nutrition. In turn, the former presented a greater proportion of components of MS (3.7% of basal hyperglycemia, 27.9% of hyperinsulinemia; 53.2% of high HOMA index; 45.6% of low HDL cholesterol; 37.7% of high triglycerides and 13.5% of hypertension) [27].

The same happens in Chilean children, in whom a prevalence of MS of 4.3% was found in those with overweight and 29.8% in those with obesity [28] and a study in Mexico where the presence of metabolic syndrome was more prevalent in teenagers that had a greater body mass index, 18.4% in those with overweight, and 58.6% in those considered obese [14]. In this regard, Weiss reported in children and teenagers, 38.7% in moderate obesity and 49.7% in severe obesity, with an increasein the risk for each higher unit of BMI [29].

In regard to the characteristics and numbers of the components of MS, we can observe that altered HDL was the prevalent factor with 26.5%, being significantly higher in females (32.5%), in cities in the interior of the province (34.8%) and in obese individuals (65.4%). Second, high systolic pressure was found in 25.3% of the sample in general, affecting 46.5% of males and 53.8% of obese individuals. In the work in Misiones, increased triglycerides and decreased HDL cholesterol were the prevalent factors [11]; while in Mexico hypertriglyceridemia was the most prevalent component (24.4%) and then abdominal obesity (20.1%)[14].

Is it important to know the number of components of MS? In a recent work, in which cardiovascular mortality was evaluated according to the number of risk factors, all individual parameters that defined MS were significantly associated, but it also inferred that risk increased gradually, from a risk factor for cardiovascular mortality and that a continuous risk existed as the number of factors increased [30].

It is relevant to observe that in our students, more than half of the sample (53.1%) already presented some component of MS, and that their number was significantly associated to the male gender and the nutrition state (obesity).

Finally, we can mention between the limitations of the work, the fact of being cross-sectional, which prevents a discussion about causality, and the lack of comparability with other national works by the used diagnostic criterion.


CONCLUSIONS
A prevalence of MS is observed, similar to that reported in different studies with variable characteristics in their components according to gender, residence and nutrition state.

The prevalence of obesity in adolescence is increasingly higher and with it, the risk associated to the development of Metabolic Syndrome and subsequent progress to type 2 diabetes and cardiovascular disease in adulthood increases. Education is essential, focused on changes in a more healthy lifestyle that may modify this profile of risk.

 

 

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