Characterisation of the somatic evolution of Portuguese children with Trisomy 21 - Preliminary results
We present preliminary results of a cross-sectional study which had the following objectives: 1- to develop percentile curves of weight, height and head circumference of Portuguese children with Trisomy 21 from 0 to 48 months of age; 2- a comparison of the growth of children with Trisomy 21 with a control population of their siblings, and 3- a comparison between the growth of Portuguese and American children with Trisomy 21 (based on the data of Cronk et al). We conclude that: 1- there is growth delay (weight, height, head circumference) in the Portuguese children with Trisomy 21, in all of the parameters evaluated and in all age groups; 2- Portuguese children with Trisomy 21 present values similar to those obtained by Cronk et al until 24 months of age; 3- from the age of 30 months onward Portuguese children with Trisomy 21 were heavier and taller than American children with Trisomy 21. This supports the usefulness of percentile curves specifically for Portuguese children with Trisomy 21.
Fernandes, A, Mourato, A, Xavier, M, Andrade, D, Fernandes, C, and Palha, M. (2001) Characterisation of the somatic evolution of Portuguese children with Trisomy 21 - Preliminary results. Down Syndrome Research and Practice , 6(3), 134-138. doi:10.3104/reports.106
Children with Trisomy 21 have well documented growth retardation, particularly with respect to head circumference.
In clinical paediatrics, and particularly in development disturbances, somatometric records (weight, height and head circumference) may be of value in supporting the diagnosis of a wide variety of disorders which effect people with Trisomy 21.
Portugal has a population of approximately ten million inhabitants, and extrapolating from the statistical findings of other countries, a prevalence of 10 to 15 thousand people with Trisomy 21 could be expected. This corresponds to 150 to 180 children born each year with this condition.
The main objectives of this study were:
- to develop percentile curves of somatic development (weight, height and head circumference) for Portuguese children with Trisomy 21, from 0 to 48 months of age;
- the comparative study of growth of children with Trisomy 21 with a population drawn from their siblings;
- and a comparison between the growth of Portuguese and American children with Trisomy 21 ( Cronk et al ., 1988 ).
Material and Methods
Based on some of the approaches in the literature ( Cronk et al ., 1988 ; Piro et al ., 1990 ; Lin et al ., 1991 ; Cremers et al ., 1996 ), we designed, in 1995, a cross-sectional study with standards which would allow clear presentation of percentile curves for weight, stature and head circumference of Portuguese children with Trisomy 21, important starting points for the development of a prospective study.
Most information was obtained during the evaluation of children with Trisomy 21 at the outpatient clinic for Trisomy 21 at the Development Centre of the Paediatric Department at Saint Maria Hospital and/or from the outpatient clinic of the Child Health Bulletin (previous files of children with Trisomy 21, aged from 0 to 10 years).
The study involved a population of Portuguese children with Trisomy 21 and their siblings with ages between 0 and 48 months followed at the Trisomy 21 Outpatient clinic.
The population consisted of:
- 196 children with Trisomy 21, representing approximately 32% of Portuguese children with Trisomy 21 aged between 0 and 48 months ( 551.060 *(1/900) = 612), from all parts of the country, thus forming a significant sample of the Portuguese children with Trisomy 21, 0 to 48 months old (none of whom were institutionalised); and
- 96 siblings of children with Trisomy 21, without known disorders.
The following approaches were used:
- Retrospective collection of anthropometric data registered in the Child Health Bulletins (children with Trisomy 21 with their respective siblings) and/or measurement, performed by one of the team members, suitably trained, during the evaluation of the development of children with Trisomy 21 followed at the Trisomy 21 clinic. Only the files with measurements taken within one week of the key dates were considered (key dates 0, 3, 6, 9, 12, 15, 18, 24, 30, 36, 42 and 48 months).
- Grouping of anthropometric data studied by gender and age, for children with Trisomy 21 and respective siblings.
- Adjustment of the subgroups obtained, using the Kolmogorov-Smirnov test.
- Homogenisation of the subgroups, excluding extreme values (mean plus or minus 4 standard deviations).
- Estimation of the mean value and standard deviation of all the parameters in the different subgroups.
- The data was plotted according to the different anthropometric parameters, to derive the percentiles curves 5%, 10%, 25%, 50%, 75%, 90% and 95%. Smoothing of the percentile curves was performed using the cubic 'spline' method.
- Comparison between the group of children with Trisomy 21 and their siblings, using Student's t test.
- Comparison between the average of Portuguese and American children with Trisomy 21.
The data was introduced in a database specially developed for such a study using Microsoft Access. The analysis of data and the graphs were done in a spreadsheet (Microsoft Excel) and using various statistical and graphical programs (DataFit, Dplot, Graphically, Statistica, SPSS).
We considered values of p <0.05 to be statistically significant.
Abbreviations: HC = Head Circumference
Note: The units of measurement are kilograms for weight and centimetres for height and HC
|Age (months)||Measurement||Boys with Tri. 21||Brothers||p|
|Age (months)||Measurement||Girls with Tri. 21||Sisters||p|
The percentile curves for weight, length/stature, and head circumference of Portuguese children with Trisomy 21 are represented in Figures 1 to 6.
Figure 1 . Percentile curves for weight of male Portuguese children with Trisomy 21
Figure 2. Percentile curves for height of male Portuguese children with Trisomy 21.
Figure 3. Percentile curves for head circumference of male Portuguese children with Trisomy 21.
Figure 4. Percentile curves for weight of female Portuguese children with Trisomy 21
Figure 5. Percentile curves for height of female Portuguese children with Trisomy 21.
Figure 6. Percentile curves for head circumference of female Portuguese children with Trisomy 21.
Figure 7 . Comparison between the medians of weight of male Portuguese and American children with Trisomy 21 (Cronk et al, 1988)
Figure 8. Comparison between the medians of height of male Portuguese and American children with Trisomy 21 (Cronk et al, 1988)
Figure 9. Comparison between the medians of weight of female Portuguese and American children with Trisomy 21 (Cronk et al, 1988)
Figure 10. Comparison between the medians of height of female Portuguese and American children with Trisomy 21 (Cronk et al, 1988)
The use of reference charts for the monitoring of weight, height and head circumference changes, is at present a familiar routine to the majority of health professionals involved in child care, and also, increasingly to many parents. The concept of percentile curve is easily understood and these data may help in the clinical diagnosis of many conditions which may affect the psychomotor development of Trisomy 21 population.
Standard reference charts are inadequate for many children, especially those with constitutional growth disturbances. Many of the situations are rare, which may transform the task of creating a growth chart difficult, if not impossible ( Hulse, 1988 ).
Concerning Trisomy 21, much has been written ( Cronk et al ., 1988 ; Piro et al ., 1990 ; Lin et al ., 1991 ; Cremers et al ., 1996 ; Hulse, 1988 ); however, the growth charts by Cronk et al . ( 1988 ) are the ones best known and used. Other percentile charts have been published, partly because the charts by Cronk et al . do not perfectly adapt to children with Trisomy 21 from other countries ( Piro et al ., 1990 ; Lin et al ., Cremers et al ., 1996 ).
In this study, we present the preliminary results for Portuguese children with Trisomy 21. The percentile curves for weight and/or height cover the ages between 0 and 48 months. Due to lack of data on head circumference for children of ages equal to or above 30 months, we decided to present only the percentile curves from 0 to 24 months groups.
There are statistical significant differences between our children with Trisomy 21 and their siblings in all of the somatic parameters evaluated and in all age groups. This fact may be due to the genetic differences between these children with Trisomy 21 and their kin, and/or endocrinologic and metabolic disturbances (maturation delay and/or hypothalamic dysfunction leading to partial deficit of growth hormone and/or growth 'insulin-like' factors) in the children with Trisomy 21 ( Annerén et al ., 1990 ).
When comparing the mean values of the weight and height of Portuguese and American children with Trisomy 21 ( Cronk et al ., 1988 ), we confirmed that the results are similar up to 24 months of age, after which Portuguese children present slightly higher values (Figures 7 to 10 ). This may be partly due to the genetic differences between the two populations studied and the time delay between both studies. Therefore, the development of percentile charts for Portuguese children with Trisomy 21 is justified.
We wish to thank all of the children evaluated, as well as the parents of children with Trisomy 21 for their collaboration as well as the financial support given by the Commission for Investigation in Health Care.
We would also like to thank Dr. Susan Marum for the English translation of the present article.
Armando Fernandes, Child Development Centre of the Paediatric Department, Hospital de Santa Maria, Av. Prof. Egas Moniz, 1599 Lisbon, Portugal, E-mail: firstname.lastname@example.org
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