|Year : 2019 | Volume
| Issue : 2 | Page : 238-244
Sonographic determination of normal subcutaneous fat thickness in children in Southern Nigeria
AI Ngaji1, EE Ekanem2, DE Bassey1, GB Inah1
1 Department of Radiology, University of Calabar, Calabar, Nigeria
2 Department of Paediatrics, University of Calabar, Calabar, Nigeria
|Date of Acceptance||23-May-2018|
|Date of Web Publication||7-Feb-2019|
Prof. E E Ekanem
Department of Paediatrics, University of Calabar, Calabar
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Subcutaneous fat is a highly active metabolic tissue that exerts control on numerous biochemical and physiological processes in health and disease. Children are particularly susceptible to nutritional problems, hence the need to measure subcutaneous fat thickness (SFT) which can be used to determine their body composition. Ultrasonography provides an affordable, noninvasive, available technique of achieving this. Objective: The aim of this study was to determine the normal values of SFT at the triceps, subscapular, and abdomen in children age 1–5 years using ultrasound in southern Nigeria. Materials and Methods: This was a prospective study of 1750 healthy children age 1–5 years in nursery and primary schools in Calabar, Nigeria. Their body mass indexes were calculated from their weights and heights, while their triceps fat thickness (TFT), subscapular fat thickness (SuFT), and abdominal fat thickness (AFT) were measured using a 7.5-MHz linear array transducer of a Hitachi portable ultrasound machine. Results: The mean TFT value for girls was 4.6 ± 2.0 mm and 3.99 ± 1.8 mm for boys. Girls had mean SuFT value of 2.37 ± 1.41 mm and boys 2.14 ± 1.02 mm. The mean AFT value for girls was 5.53 ± 2.94 mm and for boys 4.53 ± 2.37 mm. The values at all sites were generally higher in females than in males. Conclusion: This work has provided a sonographic normogram of SFT at various sites for preschool children in Nigeria.
Keywords: Children, subcutaneous fat thickness, ultrasonography
|How to cite this article:|
Ngaji A I, Ekanem E E, Bassey D E, Inah G B. Sonographic determination of normal subcutaneous fat thickness in children in Southern Nigeria. Niger J Clin Pract 2019;22:238-44
|How to cite this URL:|
Ngaji A I, Ekanem E E, Bassey D E, Inah G B. Sonographic determination of normal subcutaneous fat thickness in children in Southern Nigeria. Niger J Clin Pract [serial online] 2019 [cited 2019 Feb 17];22:238-44. Available from: http://www.njcponline.com/text.asp?2019/22/2/238/251779
| Introduction|| |
Subcutaneous fat is the fatty or adipose tissue lying directly below the skin in a region called dermis. Recent advances in molecular biology are helping to redefine the role of adipose tissue. This organ was perceived as a passive storage site for excess fat, but it is now considered a highly active, finely tuned metabolic tissue exerting control on numerous biochemical and physiological processes in both health and disease. Measurement of the thickness of subcutaneous fat is important in several areas of medicine. Its major use is in the assessment of nutritional status or in the monitoring of dietary manipulation to alter this status. The most commonly used indirect method for estimating body fat is based on measurements of subcutaneous fat tissue.
The most widely used technique for measuring the thickness of subcutaneous fat, which is often used as an estimate of whole body fat, is the skinfold calipers. Unfortunately, it is difficult to obtain accurate measurements with the caliper method, although it is simple and inexpensive, because of the compressive action of the calipers and its inability to exactly separate muscle from fat, and it is very painful in infants.
Other techniques include the total body water, bioelectrical impedance, and densitometry. Densitometry is a technique that uses air displacement plethysmography. It is extremely simple to operate, safe, and noninvasive, but it is expensive.
Total body water is based on the nutrition model of body composition. Bioelectrical impedance determines body composition based on the body's measured impedance to passing current.
Imaging modalities such as plain chest radiography, computed tomography, magnetic resonance imaging, and dual energy X-ray absorptiometry can also be used in measuring subcutaneous fat thickness (SFT), but are clearly unsuitable for neonatal and childhood studies both for technical and practical reasons ranging from cost to nonavailability, technical complexities, inaccuracy, and radiation exposure.,
Ultrasound, on the other hand, is a cheap, easy-to-operate, and readily available method of measuring SFT with no exposure to radiation. It is painless and noninvasive, and therefore the most suitable imaging modality.
The measurement of subcutaneous fat is of interest in children when determining body composition in studies of obesity and malnutrition. In our environment, many disease conditions such as protein energy malnutrition, tuberculosis, and sickle cell disease are associated with soft tissue wasting and weight loss. Oloyede et al. demonstrated that subcutaneous tissue wasting was an important differentiating feature between pulmonary tuberculosis and paragonomiasis in children. It is therefore imperative to establish the reference values for subcutaneous tissue thickness to appropriately diagnose and monitor these disease conditions. There are no known data for normal values of subcutaneous tissue thickness in Nigeria. Lagundoye and Reddy  did a study on children with kwashiorkor more than three decades ago, hence the need for this work.
Most of the techniques used in measuring SFT may be of limited use for children in our environment due to high cost, nonavailability, and exposure to ionizing radiation. Ultrasound, on the other hand, is cheap, painless, noninvasive, and readily available.
This work was therefore designed to determine the normal values of SFT in Nigerian children using B-mode ultrasonography and anthropometric parameters that affect these values.
| Materials and Methods|| |
This was a prospective study on healthy children age 1–5 years in nursery and primary schools in Calabar, Southern Nigeria. The duration of the study was 9 months. Participants for the study were healthy children age 1–5 years randomly selected from private and public schools.
This work was carried out in Calabar, Cross River State in the south-south geopolitical region of Nigeria. There are 129 registered nursery schools in Calabar; 106 (82%) are privately owned, whereas 23 (18%) are public schools. Random selection of 16 schools from the private and 4 from the public schools were carried out by balloting. In all, 350 children (20%) were from public schools, whereas 1400 children (80%) were from private schools. Two streams for each class from nursery to elementary classes were selected (each class roughly representing an age group) by balloting. All the children in the selected stream without acute or chronic illness were recruited into the study but not before obtaining duly signed informed consent from parents and guardians. Children with chronic illness, morbid obesity, genetic disorder such as sickle cell disorder or skin disorders such as burns, and those whose parents did not consent were excluded.
The materials used were 7.5-MHz linear transducer of an ultrasound machine (model EUB-405, 2008; Hitachi, Japan), acoustic gel, weighing scale, measuring tape, infantometer, and stadiometer.
Brief information such as age, sex, gender, and any history of chronic illness was taken for each child. Anthropometric measurements [weight, recumbent length, standing height, mid upper arm circumference (MUAC)] were taken using standard procedure.
Sonographic measurement of the subcutaneous fat thickness
An ultrasound system equipped with a 7.5-MHz linear transducer was used by the same investigator.
With the patient in supine position, measurements were taken at the anatomical landmarks [as shown in [Figure 1]] on the left upper arm, midway between the tip of the acromium process and the olecranon for triceps adipose tissue, and the subscapular adipose tissue below the inferior angle of the left scapula, and the abdominal adipose tissue was measured 2 cm to the left of the umbilicus.
|Figure 1: Longitudinal sonogram and schematic diagram of the subcutaneous tissue of the abdomen – A=Epidermis and dermis; B=Subcutaneous fat; C=Deep fascia; D=Skeletal muscle; E=Peritoneal cavity|
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The triceps adipose tissue was measured with the transducer held along the length of the arm. The subscapular and abdominal adipose tissues were measured perpendicular to the length of the spine. For optimal demarcation of the fat layer, the ultrasound screen was made as dark as possible. A large amount of transmission gel was used to avoid compression of the adipose tissue by the transducer. The thickness of the subcutaneous fat was measured three times with each measurement separated by an interval of a few seconds and the mean value was taken. The transducer was lifted up and repositioned before each new measurement (to avoid compression of the fat layer). The thickness was measured from the frozen ultrasound image with electronic calipers. All measurements were performed at the end of quiet inspiration. A typical examination took 5–10 min.
Method of data analysis
Data were recorded in the participant's ultrasound worksheet and transferred into Microsoft Excel (Microsoft Corporation, USA) and Statistical Package for Social Science for windows (SPSS Inc., Chicago IL, USA) version 16.0 and double-checked to ensure accuracy of the entry. Means ± standard deviation (SD), median, and 3rd to 97th percentiles were computed for each parameter for each age following the Centers for Disease Control and Prevention and World Health Organization–recognized percentiles for norms in the pediatric age group. Graphs were also derived from the percentiles computed. Pearson's correlation was used to determine the degree of relationship between anthropometric parameters and SFT at each site of measurement.
Ethical clearance for the study was obtained from the Health Ethics Committee of the University of Calabar Teaching Hospital. Written informed consent was obtained from the State Ministry of Health, the head teachers, and parent(s) before recruiting the children into the study.
| Results|| |
A total of 1750 children were recruited into the study with age ranging from 1 to 5 years. The overall mean age was 3.79 years with SD of 1.033. The mean age for girls was 3.8 years and 3.77 years for boys. The distribution of the children by age is shown in [Table 1].
The majority of the children were 4 and 5 years of age accounting for 32% and 30.4%, respectively, while only 0.34% of the children were 1 year of age. A total of 918 representing 52.46% of the children were girls and 832 representing 47.54% were boys.
The mean weight for girls was 18.77 ± 14.90 kg, whereas the mean weight for boys was 18.01 ± 8.39 kg. The mean height for girls was 1.03 ± 1.15 m and for boys 1.04 ± 3.41 m. The mean body mass index (BMI) for girls was 16.86 ± 4.9 kg/m 2 and for boys 16.72 ± 4.5 kg/m 2.
Subcutaneous fat thickness
The reference values for triceps, subscapular, and abdominal SFTs are presented as percentiles. The age-specific SFT percentile and curves for triceps, subscapular, and abdomen are shown in [Table 2], [Table 3], [Table 4]. Ten percentile values were computed (3rd, 5th, 10th, 25th, 50th, 75th, 85th, 95th, and 97th) within the age group of 1–5 years. The normal range of SFT at the three sites was within the 5th and 85th percentiles for all age group and sex. Children at less than 5th percentile were investigated for undernutrition, whereas children above 85th percentile were investigated for overnutrition. The percentiles describe the pattern of SFT development with age and the expected sex differences.
|Table 2: Percentiles for triceps fat thickness - for age (mm): Boys and girls age 1-5 years|
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|Table 3: Percentiles for subscapular fat thickness - for age (mm): Boys and girls age 1-5 years|
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|Table 4: Percentiles for abdominal fat thickness - for - age (mm): Boys and girls age 1-5 years|
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In boys, triceps fat thickness (TFT) 50th percentile ranged from 2.2 mm at 1 year to 3.4 mm at 5 years, whereas in girls, this ranged from 3.3 mm at 1 year to 4.0 mm at 5 years as shown in [Table 2] as well as [Figure 2] and [Figure 3]. The mean value for girls was 4.6 ± 2.0 mm and for boys 3.99 ± 1.8 mm.
|Figure 2: Percentile curves of triceps fat thickness for boys age 1–5 years|
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The 50th percentile for subscapular fat thickness (SuFT) in boys ranged from 1.6 mm at 1 year to 2.0 mm at 5 years as shown in [Table 3] and [Figure 4]. Similar values were recorded for girls as shown in [Table 3] and [Figure 5]. The mean value of SFT for girls was 2.37 ± 1.41 mm and for boys 2.14 ± 1.02 mm.
|Figure 4: Percentile curves for subscapular fat thickness for boys age 1–5 years|
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|Figure 5: Percentile curve of subscapular fat thickness for girls age 1–5 years|
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The 50th percentile for abdominal fat thickness (AFT) in boys ranged from 2.3 mm at 1 year to 4.0 mm at 5 years, whereas in girls this ranged for 4.3 mm at 1 year to 4.3 mm at 5 years as shown in [Table 4] as well as [Figure 6] and [Figure 7]. The mean value of AFT for girls was 5.53 ± 2.94 mm and for boys 4.53 ± 2.37 mm.
|Figure 6: Percentile curves for abdominal fat thickness for boys age 1–5 years|
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|Figure 7: Percentile curve of abdominal fat thickness for girls age 1–5 years|
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The normal range of SFT at the three sites was within the 5th and ≤85th percentiles for all age groups and sex as shown in [Table 2], [Table 3], [Table 4]. The values for TFT, SuFT, and AFT increase from 1 year and peak at 3 years, and then begin to decrease.
For the first year, the curves for boys and girls are practically super imposable especially for TFT. Generally, the values are also higher in girls than in boys of same age.
In both boys and girls, there is a positive correlation between MUAC and age, weight, height, BMI, triceps, subscapular, and AFTs as indicated in [Table 5] and [Table 6]. There is a strong correlation between the TFT and AFT with the MUAC (P = 0.0000). The AFT also correlated strongly with TFT (P = 0.0000) as indicated in [Table 5] and [Table 6].
|Table 5: Correlation of fat thickness with anthropometric parameters matrix for boys age 1-5 years|
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|Table 6: Correlation of fat thickness with anthropometric parameters for girls age 1-5 years|
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BMI correlated very strongly with sonographic measurements of fat thicknesses at the three sites (P = 0.000) as shown in [Table 5] and [Table 6]. The MUAC and fat thicknesses at the three sites correlated very strongly with BMI (P = 0.0000) as shown in [Table 5] and [Table 6].
| Discussion|| |
The preschool years (i.e., 1–5 years) are very important. This is the period of rapid and dramatic postnatal brain development and fundamental acquisition of interpersonal skills and cognitive development such as working memory, attention, and inhibition control. This is a critical period for the development of overweight and onset of obesity, and the risk increases for subsequent obesity later in adulthood. It is a time of transition from a direct maternal mediation/selection of diet-based nutrition to food selection that is based on self-selection and gratification.
As important as this is, very little work has been done in this age group with regard to the determination of body fat. A majority of the studies done involved the older children and adolescents.,, The reason for this could be that toddlers and children of preschool years are generally considered the most difficult phase of life to study because their performance is influenced by factors outside of experimental control such as emotional state, motivation, persistence, and comprehension of instruction.
Most of the studies involving this age group were done using the skinfold calipers to measure triceps, subscapular, biceps, and abdominal skinfold thicknesses.,, The skinfold calipers has several limitations such as its inability to separate muscle from fat and difficulty in obtaining accurate measurements due to its compressive effect on fat., More so, it is painful in infants and it is also difficult to complete measurement in very obese individuals and it is subject to observer error.,
This work provides the first published locally derived sonographic normograph for SFT in children age 1–5 years in Nigeria. In this study, the values for triceps, subscapular, and AFTs increased from 1 year of age reaching a peak at 3 years with a subsequent decrease in the value noted. This is similar to the pattern demonstrated by Addo and Himes  among American children using skinfold calipers. However, they recorded higher values than that obtained by ultrasound, and therefore the results may not have been as accurate as the results of this study because of the limitations of calipers as stated above , which include its inability to separate muscle from fat and its compressive effect on fat.
The decrease in fat thickness at the three sites after 3 years may be as a result of stored fat being converted to energy due to increased activity associated with increasing independency from this age onward.
SFTs at the three sites were generally higher in girls than in boys in the age group studied. This is similar to findings in other studies done in the adolescent age group in Nigeria.,, The reason proffered for this is that the girls lose fat less rapidly than boys so that they become fatter than boys to a steadily increasing degree during the period from 1–7 years when the overall width of subcutaneous fat layer begins to decrease.
SFT at all the sites correlated strongly with the anthropometric parameters of weight, height, MUAC, and BMI in the age range studied. This indicates that SFT by ultrasonography can serve as a suitable surrogate for these parameters, particularly the BMI.
With increasing prevalence of overweight, obesity, and at the same time increasing incidence of undernutrition in Nigeria, determination of SFT using ultrasonography should play an important role in pediatric clinical practice.
The normal values for SFT for all the sites (triceps, subscapular, and abdomen) as determined by this study lie between the 5th and <85th percentiles. Children at less than the 5th percentile should be investigated for undernutrition, whereas children being above 85th percentile should be investigated for overnutrition.
| Conclusion|| |
This study has provided a sonographic normogram of SFT for children in Nigeria age 1–5 years. It has also demonstrated that SFT strongly correlates with anthropometric parameters of age, sex, weight, height, mid arm circumference, and BMI. Children below 5th and above 85th percentiles should be investigated for undernutrition and overnutrition, respectively.
The authors acknowledge the assistant of Dr. Udeme Ekrikpo in analyzing the data. They are grateful to Miss Pauline Murphy who helped to prepare the article. Their gratitude also goes to the parent/guidance and who participated in the study.
With the availability, affordability, accuracy, and noninvasive nature of ultrasonography, the assessment of SFT by skinfold calipers should perhaps be abandoned considering its setbacks in this age group. Clinicians should use ultrasonography to assess adiposity.
Multicenter study in Nigeria to draw a normograph for the whole country is needed. Further studies should be done to relate SFT to the metabolic profile of these children.
Limitations of the study
There are paucity of local data and no local standards in Nigeria for comparison.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]