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On-line version ISSN 1678-4782
J. Pediatr. (Rio J.) vol.84 no.4 Porto Alegre July/Aug. 2008
Assessment of anthropometric indexes of children and adolescents with Down syndrome
Taís de S. LopesI; Daniele M. FerreiraII; Rosangela A. PereiraIII; Gloria V. da VeigaIV; Vania M. R. de MarinsV
Programa de Pós-Graduação em Nutrição, Universidade
Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, Brazil
IIDoutora. Professora adjunta, Faculdade de Nutrição, Universidade Federal Fluminense (UFF), Niterói, RJ, Brazil
IIIDoutora. Professora adjunta, Instituto de Nutrição Josué de Castro (INJC), UFRJ, Rio de Janeiro, RJ, Brazil
IVDoutora. Professora associada, INJC, UFRJ, Rio de Janeiro, RJ, Brazil
VDoutora. Coordenadora, Curso de Nutrição, Faculdade Arthur Sá Earp Neto, Petrópolis, RJ, Brazil
To compare the agreement in the classification of the weight-for-age (W/A) and
height-for-age (HA) indexes for children and adolescents with Down syndrome
(DS) according to selected international reference distributions.
METHODS: A cross-sectional study was carried out in children (2 to 9.9 years old) and adolescents (10 to 17.9 years old) with DS from cities in the state of Rio de Janeiro, Brazil, in 2005. The W/A and H/A indexes were classified according to the percentiles of two curves developed for individuals with DS and one distribution developed for healthy subjects. The cut-off limits applied for categorization were: below the 5th percentile (< P5) and above the 95th percentile (> 95). The weighted Kappa index was estimated to assess agreement between the classifications (p < 0.05).
RESULTS: Information was obtained on 98 children and 40 adolescents. From 1.0 to 18.4% of the children were < P5 for W/A, and the agreement for this index was considered weak (Kappa = 0.16; 95%CI -0.03-0.34; p < 0.01); no agreement was observed between the H/A classifications. For adolescents, W/A < P5 varied from 2.5 to 5.0%; once more there was no agreement for this classification (Kappa = 0.16; 95%CI -0.15-0.48; p > 0.05). There was good agreement for the H/A index (Kappa = 1.00; 95%CI 0.23-1.00; p < 0.01).
CONCLUSION: There was weak agreement between classifications of anthropometric indexes according to three different distributions. The data indicated that the construction of specific curves for individuals with DS would facilitate the identification of overweight, which is often observed among these patients.
Keywords: Nutritional assessment, children, adolescents, Down syndrome, anthropometry, weight-for-age, height-for-age.
Down syndrome (DS) is a genetic anomaly in the 21st pair of chromosomes which has an extra chromosome (trisomy 21). This abnormality causes physical and mental impairment, such as muscular hypotonia (in particular oral), congenital heart disease, reduced immunity, gastrointestinal disorders, obesity, delayed psychomotor development and neurological problems, and hearing and sight deficiencies.1,2
Growth occurs in a different way among children with DS and it is characterized by earlier onset of the growth spurt and reduced linear growth velocity, which results in shorter stature than general population.3-13 There is also a predisposition to overweight, particularly among adolescents and adults7,14,15 that may itself be related to the growth deficiency since it reduces energy requirements. In addition to being a risk factor for metabolic disorders, overweight is an aggravating factor for other conditions that affect this group, such as heart diseases and muscular hypotonia. Therefore, nutritional assessment of children and adolescents with DS is important to enable the diagnosis and monitoring their nutritional conditions.
Percentile distributions of anthropometric indexes, such as weight-for-age (W/A), weight-for-height (W/A) and height-for-age (H/A) specific for children and adolescents with DS have been developed reflecting the lower growth velocity and the restricted height observed in this group. The distribution compiled in the United States6 is one of the most often cited in the literature4,5,10-12,16,17 and has distributions for weight, height and head circumference by age (HC/A), according to sex and covering the age group from 2 to 18 years.
In Spain,8,9 distributions have been established for children and adolescents with DS from 3 months to 17 years of age including the same indexes covered by the United States distribution.7 In Sweden4and in the United Kingdom and Ireland,5 specific distributions have been compiled for weight, height/length and head circumference, by age group and sex, from birth to 18 years of age.
In Italy, Piro et al.13 developed curves for weight, length/height and head circumference for children with DS from 0 to 5 years of age. In Saudi Arabia, Al Husain18also compiled curves by age group and sex, for weight, length/height, head circumference and weight for length/height for children from 0 to 5 years of age with DS and compared them with curves developed for children of the same group but without this condition.
In Brazil, Mustacchi19 carried out a longitudinal study with 174 children from 0 to 8 years of age with DS, in the urban zone of São Paulo, between 1980 and 2000. The author assessed weight, height and head circumference and compiled distributions for the indexes H/A, W/A and HC/A, according to age group and sex. In this country there studies investigating assessment of anthropometric indexes in children and adolescents with DS are scarce. There is also no record of studies investigating the use of specific distributions for people with DS. The objective of this study is to assess the agreement between three different classifications of the W/A and H/A indexes of children and adolescents of both sexes with DS: two developed specifically for individuals with DS (in the United States6 and in Spain8,9) plus the reference distribution recommended by the World Health Organization (WHO).20,21
A cross-sectional study was carrried out in children (aged 2 to 9.9 years) and adolescents (aged 10 to 17.9) with DS from both sexes, assisted at selected philanthropic institutions and selected from four cities in the state of Rio de Janeiro, Brazil: Niterói, São Gonçalo, Duque de Caxias and Rio de Janeiro. Pretest and pilot studies were carried out for all fieldwork procedures at similar institutions in the same state (Petrópolis, RJ).
All children and adolescents registered at these institutions that met the inclusion criteria were examined: clinical or genetic (karyotype) diagnosis of DS and no physical disability that could prevent anthropometric assessment.
The sample was characterized according to data on family income and parents' educational level obtained by a structured questionnaire. Monthly per capita family income was calculated by dividing the total family income by the number of people living in household and then categorized into multiples (or fractions) of the monthly minimum wage that was effective at the collecting data period (R$ 300.00/US$ 125.00). The parents' educational level was recorded as the highest grade concluded with approving.
Measurements were taken with the children and adolescents wearing minimum clothing, no shoes, and no ornaments or jewelry. They were weighed using a Kratos-Cas portable electronic scale with 150 kg capacity and 50 g precision. Height was measured twice using a Seca® (model 206) stadiometer accurate to 0.1 cm, if the difference between measurements was greater than 0.5 cm the mesurements were repeated. The mean of the two measurements was used in the analysis.
The statistic analysis included the estimation of absolute and relative frequencies for the variables describing the sample characteristics as well weight and height means (and respective 95% confidence interval - 95%CI).
The indexes analysed were W/A and H/A, since the reference distributions specific for individuals with DS from the United States6 and from Spain8,9 only presented data for these indexes. The same indexes were also estimated according to the distributions proposed by the WHO,20,21 which are the references used by the Brazilian Ministry of Health to assess the growth of children and adolescents in the general population.22
The distributions were compared taking into account the following cutoff points: for the W/A index, below the 5th percentile (P5), between P5 and the 95th percentile (P95) and above P95; for the H/A index the cutoff was above or below P5. These cutoff points were chosen since they are provided by the adopted distributions and are used as indicators of possible underweight (P5, W/A), overweight (P95, W/A), and stunting (P5, H/A). It is expected that 5% of the children and adolescents would be classified below P5 and 5% above P95 according to each distribution.
The W/A index was utilized only for the DS-specific distributions comparison for adolescents. This index is not recommended for evaluation of adolescents, at this phase of development, which can lead to misleading interpretations. The body mass index (BMI) = weight/height-for-age2 is the indicator of choice for adolescents because they can be at different stages of pubertal maturity and consequent changes in the body composition, even at the same cronological age.
The weighted Kappa (and 95%CI) was estimated in order to evaluate agreement between the classifications of W/A and H/A indexes according to the three distributions. The Kappa values were interpreted according to following: Kappa < 0.40, weak agreement; Kappa 0.40 - 0.75, good agreement; Kappa > 0.75, excellent agreement. If Kappa is zero, any agreement observed can be explained by chance. Negative values for Kappa means that the observed agreement is less than would be obtained by chance. Finally, Kappa value equal to one means that the agreement is excellent.24 Statistical significance was considered for p < 0.05.
This project is in compliance with Ministry of Health resolution 196/9625 and has been approved by the Research Ethics Committee at the Hospital Universitário Antônio Pedro/Medical Faculty/Universidade Federal Fluminense (hearing number 142/04). The children and adolescents were authorized to participate by parents or guardians, who signed free and informed consent forms after receiving information on all of the procedures used in the investigation.
The philanthropic institutions studied had a total of 157 children and adolescents with DS enrolled (83 boys and 74 girls) in the age group of interest. It was not possible to obtain information on19 (12.1%) subjects either because their parents or guardians refused permission or because they were not able to undergo anthropometric measurement. A total of 138 individuals were examined (72 boys, 52.2%; 66 girls, 47.8%), of whom 98 (71.0%) were children aged 2 to 9.9 years (46 boys and 52 girls) and 40 were adolescents (26 boys and 14 girls) (Table 1).
The median monthly family income per capita was 0.5 minimum wage. Educational level of the fathers showed that 74% studied up to the fourth grade of elementary school. In contrast, 24% of the mothers had 4 years or less at school and 28% had completed the high school (11 years' study) (Table 1).7
Table 2 lists the characteristics of the group investigated in terms of weight and height (means and 95%CI) broken down by age group.
The proportion of children below P5 for the W/A index varied from 1.0%, according to the distribution from the United States,6 to 18.4%, according to the Spanish distribution.8,9 The Spanish8,9 and the WHO distributions 20 classified 4.1% of the children above P95 for W/A, whereas, according to the distribution from the United States,6 16.3% were above this limit and none of the children were below P5 for H/A. However, according to the Spanish distribution8,9 and to the WHO,20 20.4 and 55.1%, respectively, were considered to be below the P5 for the H/A index (Table 3).
According to the distribution from the United States,6 5.0% of the adolescents were classified as below P5 for W/A, whereas the Spanish8,9 distribution defined 2.5% as below this level. Adolescents were only classified above P95 for W/A in relation to the distribution from Spain8,9 (17.5%). The H/A index analyzed according to the DS-specific distributions revealed that 2.5% of the adolescents were classified as below P5. On the other hand, the WHO distribution,21 classified 60.0% of the adolescents below the P5 for the H/A index.
For the children, there was little agreement (Kappa = 0.29; 95%CI 0.20-0.37; p < 0.01) between W/A classifications according to the three distributions. The same degree of agreement was observed between the classifications based on the distributions from the United States6 and Spain8,9 (Kappa = 0.16; 95%CI -0.03-0.34; p < 0.01). The same was also observed with relation to the comparison of the W/A classification according to the distribution from the United States6 and the WHO20 (Kappa = 0.26; 95%CI 0.04-0.48; p < 0.01). Good agreement was observed between the W/A classification according to the distribution from Spain8,9 and the WHO classification20 (Kappa = 0.50; 95%CI 0.29-0.72; p < 0.01) (Table 4).
The H/A classifications according to all three distributions taken together had agreement close to zero (Kappa = 0.02; 95%CI -0.09-0.13; p > 0.05). When the distributions were compared in pairs, no agreement whatsoever was detected (United States6 vs. Spain8,9 and United States6 vs. WHO:20 Kappa = 0.00; p > 0.05; Spain8,9 vs. WHO: Kappa = 0.00; 95%CI -0.15-0.05; p > 0.05) (Table 4).
For the adolescents, weak agreement was observed in the comparison of the W/A classified according to the DS-specific distributions (Kappa = 0.16; 95%CI -0.15-0.48; p > 0.05). Similarly, no agreement was observed for the H/A index when all three distributions were considered (Kappa = -0.13; 95%CI -0.30-0.04; p > 0.05). For H/A, excellent agreement was observed (despite a wide confidence interval) for the classifications by the DS-specific distributions (Kappa = 1.00; 95%CI 0.23-1.00; p < 0.01) and no agreement when these classifications were compared with that estimated according to the distribution adopted by the WHO21 (Table 4).
The results demonstrate high proportion of children classified below P5 for W/A according to the distribution from Spain8,9 and the distribution developed for healthy individuals.20 Conversely, the distribution from the United States6 resulted in an elevated proportion of children categorized above P95. In contrast with the results for the children, the Spanish distribution8,9 classified a higher proportion of the adolescents above P95 than did the distribution from the United States,6 indicating that the Spanish distribution possibly has greater sensitivity in the detection of overweight among adolescents with DS. These data suggest that the adolescents studied here possibly do not present underweight.
Analysis of the H/A index showed divergent results for children according to the three reference distributions. Whereas for the adolescents the data analyzed according to the specific distributions indicated that their growth did not differ substantially from that of adolescents with DS originating from other population groups (Spain and United States).
Despite recognizing the elevated prevalence of heart diseases among people with DS and their repercussions for nutritional status, in this study the effect of these conditions was not considered in analyses, since the study intended purely to compare how the individuals would be categorized by the different distribution references. Another limitation of this study is the reduced number of individuals in the age and sex categories, particularly among the adolescents.
These findings indicate the need to carefully evaluate the nutritional situation of adolescents with DS. If the adolescents in this study had been assessed solely using the distribution from the United States,6 it would not have been possible to identify overweight among them. Assessment using the Spanish distribution,8,9 in contrast, makes it possible to implement interventions to reduce the weight of those categorized above P95 for W/A, which could reduce the development of possible metabolic disturbances which would be caused by excess body fat.
Furthermore, the use of H/A distributions developed for healthy individuals is inappropriate for assessing the growth of people with DS; therefore, it is recommended the development of specific reference distributions to monitor the growht of individuals with the DS.
The weight-for-height and BMI-for-age indexes, which assess the harmony between the dimensions body mass and height, were not investigated in this article based on the fact that the two distributions developed for individuals with DS6,8,9 do not provide data for these indexes.
The distribution published by Mustacchi et al.,19 which was compiled in Brazil, was not used in this study because it only covers the age group from 1 to 8 years of age. Furthermore, for operational reasons, two other distributions4,5 developed for individuals with DS were also not used in the analysis. A distribution developed in Sweden4 does not present the curves in percentiles, whereas a distribution developed in the United Kingdom and Ireland5 does not provide the 5th and 95th percentiles.
Myrelid et al.5 also compared anthropometric data from Swedish children and adolescents with DS with the DS-specific distribution from the United States.6 The authors observed discrepancies such as, for example, the mean height of the Swedish DS subjects at 18 years of age was greater than that of the individuals from the United States. In terms of weight, the authors observed the inverse relationship: the mean weight of the Swedish adolescents with DS at 18 years corresponded to the 50th percentile for boys and the 25th percentile for girls on the distribution from the United States.6 The authors attributed these differences to ethnic diversity and the different sample sizes.
In Portugal, Fernandes et al.10 examined 196 children aged 0 to 48 months with DS and 96 siblings of these children who did not have DS. When they compared their results with the DS-specific distribution from the United States.6 The authors observed that the Portuguese children had a similar growth to those in the United States up to 24 months of age, but, from 24 to 48 months, they exhibited higher values for length and weight.
In a study carried out in Chile, Pinheiro et al.16 conducted research with 116 children and adolescents with DS, aged from 3 months to 18 years. These authors assess agreement between diagnoses of W/A and H/A indexes according to the DS-specific distributions from the United States6 and Spain8,9 and also with the National Center for Health and Statistics (NCHS) curves.26 The authors observed that there was very little agreement between the distributions in terms of the indexes analyzed; nevertheless, they indicated that the distribution from Spain was more appropriate for assessing nutritional disorders among these children.
There is no consensus related to reference distributions and classification criteria to be used for assessing the nutritional status of children and adolescents with DS. Although specific distributions have already been developed in some countries,3-6,8-10,12,13,18 there are no records of studies carried out in Brazil which have compiled weight and height distributions from a representative sample of individuals with DS. The need to use distributions produced specifically for this group is based on the recognition that their growth and development is different.
The weak agreement observed between the distributions analysed indicates that carrying out longitudinal studies with representative samples of individuals with DS in Brazil would be of great utility to understanding the process of growth and development in these children and adolescents and would allow the development of reference distributions specific to this population group. Such studies would make it possible to construct specific curves, which would be an aid in the identification of the weight alteration, primarily overweight, which are often observed in this group.
The authors would like to thank Professor Luzia Giannini Cruz for her help with fieldwork and Professor Renan Moritz Varnier de Almeida for help analyzing the data. The authors are also grateful to the students Anna Caroline Mendes Cardoso, Letícia Ferreira and Thais Fernandes.
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Correspondence: No conflicts of
interest declared concerning the publication of this article. Suggested citation:
Lopes TS, Ferreira DM, Pereira RA, da Veiga GV, de Marins VM.Assessment of anthropometric
indexes of children and adolescents with Down syndrome. J Pediatr (Rio J). 2008;84(4):350-356.
Rosangela Alves Pereira
Universidade Federal do Rio de Janeiro
Instituto de Nutrição Josué de Castro
Departamento de Nutrição Social Aplicada
Av. Brigadeiro Trompowsky, s/nº - CCS - BLOCO J - 2º ANDAR - Ilha do Fundão
CEP 21941-590 - Rio de Janeiro, RJ - Brazil
Tel.: (21) 2562.6679
Manuscript received Dec 27 2007, accepted for publication May 28 2008.
No conflicts of
interest declared concerning the publication of this article.
Suggested citation: Lopes TS, Ferreira DM, Pereira RA, da Veiga GV, de Marins VM.Assessment of anthropometric indexes of children and adolescents with Down syndrome. J Pediatr (Rio J). 2008;84(4):350-356.