Socioeconomic disparities in adolescent growth: an anthropometric study of Nigerian school children in Lagos

Abstract

Background

The dearth of literature on studies investigating the influence of various factors impacting adolescent growth patterns in African populations remains a major challenge in growth research. The aim of the current study was to assess the variation in anthropometric dimensions estimated from stature and limb parameters of adolescent Nigerian school children based on socio-economic backgrounds in Lagos, using school type as an indicator.

Method

Ethical clearance was sought and obtained, and upon full consent of the participants, anthropometric measurements of stature, arm span, thigh, percutaneous tibial, arm, forearm, hand and foot lengths were taken from 640 adolescent school children (320 males and 320 females), aged 10–17 years, selected from public and private schools in Lagos using a systematic random method. The anthropometric protocols adopted were those recommended by the International Society for the Advancement of Kinanthropometry (ISAK); and the data collated was analyzed using descriptive statistics and inferential tests such as t-tests to determine significant differences between groups.

Result

We observed statistically significant differences in the mean of measured anthropometric dimensions between age matched private and public-school boys {Stature (167.69:160.33; p = 0.000*), Thigh length (45.92:42.66; p = 0.000*), Percutaneous tibial length (37.73:34.55; p = 0.000*), Arm length (28.89:26.81; p = 0.000*), Forearm length(26.14:23.65; p = 0.000*), Hand length (18.26:17.66;p = 0.004*), Foot length(25.07:24.08; p = 0.000*), Arm span (165.73:152.27; p = 0.000*)}, and girls {Stature (166.29:161.61; p = 0.000*), Thigh length (47.98:43.95; p = 0.000*), Percutaneous tibial length (37.43:35.35; p = 0.000*), Arm length(28.76:27.35; p = 0.000*), Forearm length (25.52:24.53; p = 0.002*), Hand length (18.07:17.76;p = 0.000*), Foot length(24.21:23.89; p = 0.023*), Arm span (164.19:154.25; p = 0.000*)}.

Conclusion

Significant male-female differences in anthropometric dimensions were greater in public than private schools, with the females exhibiting higher values than the males in the public schools, and the males recording higher values than the females in the private schools showing that school types are indicative of socio-economic status. The observed variations in anthropometric dimensions among the study population may reflect a complex interaction between growth and socio-economic status, as these factors have been found to influence adolescent growth patterns.

Introduction

Adolescents experience a critical transition from childhood to adulthood, which is characterized by rapid physical growth, psychological development, and social changes [1]. During this developmental period, the relatively uniform growth in childhood is suddenly altered by an increase in growth velocity, a sudden spurt that is influenced by sex, genetic, socioeconomic, environmental and psychological factors [2, 3].

A myriad of biological changes occur during adolescence which include sexual maturation, increase in height and weight, completion of skeletal growth accompanied by a marked increase in skeletal mass and changes in body composition. The succession of these events is consistent among adolescents. However, there may be a great deal of deviation in the age of onset, duration, and tempo of these events between and within individuals. For this reason, adolescents of the same chronological age can vary greatly in physical appearance. This has direct relevance for the nutrition requirements of adolescents [4].

The socioeconomic background and lifestyle factors that often influence patterns of nutritional intake, physical activity and other environmental stresses that affect the development of anthropometric dimensions appear to manifest significantly during the adolescent growth period [5]. These elements probably combine to mask the underlying growth pattern, thus; the widening margin of the inequalities between the poor and the better-off appears to be manifesting in the varying patterns of physical growth [6,7,8,9,10].

During childhood and adolescence, sexual dimorphism usually results from different growth velocities in both sexes. In comparison to the males, the females grow faster. The latter follows the typical human growth curve with a higher tempo and finishes their length growth earlier. After the adolescent growth spurt, the growth velocity decelerates but not in all dimensions, hence, males show a clear growth advantage in adulthood because of their later and longer-lasting growth spurt i.e., more years of physical growth [11, 12].

It is important to note that while the role of socioeconomic status (SES) in influencing growth patterns is undisputable, emerging frameworks such as the Socio-Economic-Political and Emotional (SEPE) model by Bogin [13] provides a broader perspective on growth regulation. This model includes not only traditional socio-economic factors but also psychological and emotional elements that may influence physical development. Also, studies have shown the significant role of parental education in determining body height [14, 15].

Previous studies have reported the status of frame size variation in adolescent male [16] and female [17] in Nigerian school children in Lagos. Similar studies on the growth pattern of adolescent male Nigerian schoolchildren [18] and the anthropometric evaluation of growth variation of adolescent females in urban Lagos [19] have also been reported. However, studies investigating the patterns of growth variation based on the anthropometric evaluation of stature and limb dimensions in adolescent Nigerian school children are scanty in the literature. Therefore, this study aimed to characterize the growth patterns of anthropometric parameters in adolescent Nigerian school children, using stature and limb dimensions. Specifically, to investigate the influence of socioeconomic status, indicated by school type on these anthropometric dimensions. The hypothesis is that significant differences exist in these dimensions based on school type and sex.

Method

Study design

Cross-sectional study design was used to investigate the variation in anthropometric dimensions estimated from stature and limb parameters of adolescent Nigerian school children based on socio-economic backgrounds in Lagos, using school type as an indicator.

Study population

This cross-sectional study comprised 640 adolescent Nigerian school children (320 males and 320 females), aged 10–17 years who volunteered and satisfied the eligibility criteria. The participants were selected by multistage stratified random sampling from two secondary schools, the International School, University of Lagos with an estimated population of about 1000 pupils (constituting the middle to high-income SES group) and Oduduwa Secondary School, Mushin with an estimated population of about 1200 pupils (constituting the low-income SES group). The International School, University of Lagos, and Oduduwa Secondary Schools both involved 320 subjects each (160 males and 160 females), uniformly represented by 20 subjects for each of the 8 age groups cutting across the selected age range in the study (10–17 years). The SES classification protocol employed in this study was modified from previous studies [9, 20]. To ensure widespread of parental roots, various Nigerian ethnic nationalities were represented in the study and they include the Yoruba, Igbo, Hausa-Fulani, Edo, Ijaw, Ibibio, Efik, Igala, Nupe, Idoma, Tiv and Annang. Thus, allowing transmission of genetic traits from parent to offspring in a Mendelian heterogeneous manner.

An online sample size calculator was used to calculate the sample size [21]. To get the results that reflected the target population in terms of gender and age as precisely as needed, a 95% confidence interval (1.96 confidence interval of a population of 2,200) was assumed and a 4% margin error. Sample Size was calculated using the Cochran formula [22] where n = 600.25 (calculated sample). To increase the power of the study, this was rounded up to 640 ( the total population size used for this study). The sample size was adjusted to account for non-response and improperly filled questionnaires.

Ethical approval and consent to participate

Ethical clearance to conduct this study was sought and obtained from Health Research Ethics Committee, College of medicine of the University of Lagos and the study was observed in accordance with the principles outlined in the Declaration of Helsinki with respect to research on human subject. Written approval obtained from the authorities at the Mushin Local Education District of the Lagos State Universal Basic Education Board (SUBEB) and from the authorities at the University of Lagos International School enabled access to the study participants. Written informed consents were given by the participants before measurements were taken, which required the appendage of the signature of their parents/guardians on the consent forms as the prerequisite for the commencement of measurement. The right to withdraw, if so desired at any stage of the study was also clearly stated to the participants.

Eligibility criteria

This required the participants to be within the age range, enrolled in either University of Lagos Secondary School or Oduduwa Secondary School in Lagos and have both parents of Nigerian ancestry as confirmed from the school records. Excluded from the study were the obese, acutely-ill and physically challenged children with poor health conditions that manifested with overt signs of stunted growth. Also excluded were those who presented apparent symptomatic musculoskeletal, dermatological or congenital deformity that might affect the anthropometric measurements.

Out of the 700 adolescents initially screened for participation, 60 were excluded from the study due to failure to meet the inclusion criteria or lack of parental consent. As a result, a final sample of 640 participants (320 males and 320 females) was included in the analysis.

Anthropometric data collection

Materials

• a. Stadiometer: Alpha 220, SECA™ Stadiometer (Germany), with a measuring range of 60–200 cm. For this study, it was used for stature measurement.

• b. Segmometer: This custom-made instrument was manufactured from a steel tape 100 cm long and at least 15 mm wide which has attached two straight branches, each approximately 7–8 cm in length. For the present study, the segmometer was used to measure thigh, percutaneous tibial, arm, forearm and hand lengths.

• c. Large sliding caliper: A Rosscraft™ Campbell Anthropometry kit caliper 20 (Rosscraft, Canada) with two straight branches that allow measurement of large bone breadths. For the present study, the large sliding caliper was used for foot length measurement.

• d. Lufkin steel tape: A Lufkin W606PM flexible steel tape, non-extensible, no wider than 7 mm and have a stub of at least 4 cm before the zero line. For this study, it was used to measure the arm span.

Methods

The anthropometric parameters measured include stature, thigh length, percutaneous tibial length, arm length, forearm length, hand length, foot length and arm span, which were according to the anthropometric protocols recommended by the International Society for the Advancement of [23], with the measuring instruments read and recorded to the nearest 0.1 cm for all the measurements.

• a. Stature: The subject was required to stand with the feet together, with the heels, buttocks and the upper part of the back touching the scale of the stadiometer. The head was held in the Frankfort plane and this was achieved when the Orbitale (lower edge of eye socket) was in the same horizontal plane as the tragion (the notch superior to the tragus of the ear). With the hands of the measurer placed far enough along the line of the jaw of the subject to ensure that upward pressure is transferred through the mastoid process, the subject was instructed to take and hold a deep breath. The head board of the stadiometer was then placed firmly down on the vertex.

• b. Thigh length: With one branch of the segmometer placed on the marked Trochanterion site, and the other end placed on the marked Tibiale laterale site, the thigh length was measured as the distance between the marked anatomical landmarks.

• c. Percutaneous tibial length: One branch of the segmometer was placed on the marked Tibiale mediale site and the other is positioned on the marked Sphyrion site. The distance between the two landmarks was measured and this represents the tibial length.

• d. Arm length: One branch of the segmometer was held on the marked Acromiale site, while the other was placed on the marked Radiale site. The distance between the two landmarks was measured and this represents the arm length.

• e. Forearm length: With one branch of the segmometer held against the Radiale site and the other branch placed on the Sphyrion landmark, the distance between the two landmarks was measured and this represents the forearm length.

• f. Hand length: Using the segmometer, this measurement was taken as the shortest distance from the marked Midstylion line to the Dactylion.

• g. Foot length: Using a large sliding caliper, the distance between the Akropodian and the Pternion was measured and this represents the length of the foot.

• h. Arm span: It was ensured that the participant’s head was in the Frankfort horizontal plane and the arms were outstretched at right angles to the body with palms facing forward. The length from the tip of the middle fingers of the left and right hands when raised parallel to the ground at shoulder height at a one-hundred-and-eighty-degree angle was then measured with a Lufkin steel tape.

Quality control

Tester/measurer preparation

Preparations for the anthropometric measurements included the training of the measurer in anthropometric techniques consistent with the competence level of anthropometry technician Level 1 according to the protocol recommended by the International Society for the Advancement of Kinanthropometry (ISAK). This training was undertaken by the second author, who is an ISAK-certified Anthropometry Technician Level 2. The measurer and assistant were post-graduate students in the Department of Anatomy, College of Medicine of the University of Lagos. The measurer had reliability testing as part of the training, aimed to achieve technical errors within internationally accepted limits. All measurements were taken by the trained tester/measurer.

Measurement error

To determine measurement error intrinsic to this study, technical error of measurement (intratester and intertester) was employed as a measure of validity. The subjects, variables and measurement procedures used for the two types of TEM were the same but the tests had to be carried out independently. Since one of the testers is a certified anthropometrist, the intertester TEM was used as a measure of accuracy. The TEM provides an estimate of the measurement error in the units of measurement of the variable. This value indicates that two thirds of the time a measurement should come within +/- of the TEM.

Statistical analysis

The data collated was analyzed using Statistical Package for the Social Sciences (SPSS) for windows, version 20.0, Armonk, New York: IBM Corporation. Kolmogorov-Smirnov test was employed to test the normality of the sample. All the data were analyzed for mean and standard deviation. The student t-test was used to analyze the differences between independent groups at a 95% confidence interval (P < 0.05).

Results

The results obtained were summarized using the tables. The Kolmogorov-Smirnov test revealed normal data distribution, with the test statistics found not to be statistically significant (P > 0.05) for all the parameters employed in the study.

Table 1 presents summary of the descriptive statistics and sex differences of anthropometric parameters for the Private school boys and girls. From the table, it can be observed that the Private school boys exhibited greater values for the anthropometric dimensions than the Private school girls, except for thigh length. However, the differences were statistically significant only for forearm length and foot length, with P values of 0.016 and 0.000 respectively. The Private school girls recorded greater thigh length value than the Private school boys, with t and P values of -4.46 and 0.000 respectively. The differences are statistically significant at P < 0.05.

Table 2 shows summary of the descriptive statistics and sex differences of anthropometric parameters for the Public school boys and girls. From the table, it can be observed that the Public school girls recorded higher values in the anthropometric parameters than the Public school boys, except for foot length. However, the differences were statistically significant for thigh, percutaneous tibial, arm and forearm lengths, with P values of 0.016, 0.047, 0.048 and 0.002 respectively. The differences are statistically significant at P < 0.05.

Table 3 shows differences in anthropometric parameters of the public and private school boys as an indicator of socio-economic status. From the table, it can be observed that there exist highly statistically significant differences in the anthropometric dimensions of the Private and Public school boys, with the Private school boys exhibiting predominantly greater values in all the parameters considered in this study.

Table 4 shows differences in anthropometric parameters of the public and private school girls as an indicator of socio-economic status. Here, it can be seen that the Private school girls recorded predominantly higher values in the anthropometric dimensions than the Public school girls. It can also be observed that the differences were all significant statistically, at 95% confidence interval.

Table 1 Summary of the descriptive statistics and sex differences of anthropometric parameters for the private school boys and girls

Table 2 Summary of the descriptive statistics and sex differences of anthropometric parameters for the public school boys and girls

Table 3 Differences in anthropometric parameters of the public and private school boys as an indicator of socioeconomic status

Table 4 Differences in anthropometric parameters of the public and private school girls as an indicator of socioeconomic status

Discussion

Social gradients as a basic category of variation in growth pattern [24,25,26,27] was demonstrated in the present study, as significant differences in body size and maturation rate as indicated by anthropometric measurements such as stature, arm span, and limb lengths, were observed within a society between groups differing in some aspects of their socio-economic situations. According toPsaki et al., (2014) socio-economic status (SES) can be defined as a theoretical construct encompassing individual, household, and/or community access to resources. It is commonly conceptualized as a combination of economic, social and work status, measured by income or wealth, education, and occupation, respectively. SES has been linked to a wide range of health-related exposures and outcomes, including child undernutrition, chronic disease and infection [28,29,30].Ibeabuchi et al., (2015b) opined that the non-applicability of some of the traditional indices of SES to many developing countries has been highlighted [20], making it pertinent to adopt simpler and easily-verifiable criteria. Additionally, the use of proxies for SES such as residence area and the type of school attended has been reported [17, 19, 31]. As for the latter, economically advantaged families often prefer fee-paying private schools over minimal-fee-paying public schools because the former are better funded and provide superior educational facilities and a more positive learning environment [32].

From the present study, private school participants (boys and girls) exhibited consistently higher mean values than their public-school counterparts in all the anthropometric parameters, which include stature, thigh length, percutaneous tibial length, arm length, forearm length, hand length, foot length and arm span. This indicated that the differences in anthropometric dimensions based on SES were highly significant statistically, for all the measured variables. This is in consonance with the reports from previous similar growth studies on children [17, 19, 33,34,35] which found that the middle to high income group of the populace exhibited greater anthropometric values than the low-income groups. These findings further highlight the underlying effects of SES on growth, as it has been reported that low socio-economic factors such as poor food consumption pattern, illness, lack of sanitation, poor hygienic practices, inadequacy of parents’ education and other handicaps of poverty appear to be far more decisive than genetic predisposition in producing deviations from the normal reference growth patterns [36]. The variations observed between the two socioeconomic backgrounds may reflect the disparity associated with the onset of the adolescent growth spurt which can be due to the influence of many exogenous factors relative to socio-economic background [17, 19]. However, while socioeconomic status (SES) significantly contributes to growth patterns, previous research has also shown evidence of a community effect [37], whereby children tend to grow in relation with their community’s average height, irrespective of their individual socioeconomic or nutritional status. This phenomenon suggests that tall communities generate tall individuals even in unfavorable conditions and demonstrates that being short may not necessarily indicate poor nutrition, health, or socioeconomic status but rather reflect the norm within their community.

The present study also recorded sex differences in the anthropometric parameters of the private and public school sample. It was observed that statistically significant sexual dimorphism was more dominant in the public than the private school. The females in the public school recorded consistently higher values than their male counterparts for all the parameters except the foot length. When compared with the trend for sexual dimorphism in adults (> 18 years), it can be observed that anthropometric studies on adult populations in different climes usually report dominantly higher values for the males than the females. These previous reports on sex differences in stature [11], thigh length [38], percutaneous tibial length [39], arm length [40], forearm length [41], hand length [42], foot length [43] and arm span [44]; and a plethora of other similar studies have all reported significantly higher values for the males than the females; showing a pattern different from the adolescents of the public school involved in the present study. This variation in trend, hence the equality or less significant sex differences, or even greater adolescent female anthropometric values than the males can be explained on the basis that during childhood and adolescence, sexual dimorphism usually result from different growth velocities in both sexes. In comparison to the males, the females grow faster. The latter follow the typical human growth curve with a higher tempo and finish their length growth earlier. After the adolescent growth spurt, the growth velocity decelerates but not in all dimensions, hence males show clear growth advantage in adulthood because of their later and longer lasting growth spurt i.e., more years of physical growth [11, 12, 45]. While the present study has focused on socio-economic status as a key determinant of growth patterns, recent research has expanded our understanding of growth regulation to include socio-political and emotional factors, as outlined in the SEPE model [13]. In addition, studies have demonstrated that the level of parental education are strongly correlated with body height, with influences extending beyond access to nutrition to include factors such as emotional and self-confidence that contribute to overall child health [14, 15].

Strengths, weaknesses and limitations

The main strengths of the present study are that it provides a valuable contribution to understanding the relationship between socio-economic status (SES) and adolescent growth patterns by using school type as a practical and measurable proxy for SES. The large sample size and inclusion of both public and private schools enhance the generalizability of the findings. Additionally, the study’s focus on sex differences in anthropometric dimensions offers a nuanced understanding of adolescent growth dynamics, particularly the differential impact of SES and the timing of growth spurts between sexes. These findings serve as important reference data for growth research and public health strategies targeting adolescent populations in Africa.

The major limitations of the study are the use of school type as an indicator for SES, while practical, may not fully capture the multidimensional nature of socio-economic disparities, including parental education and income levels. Also, the present study’s cross-sectional design precludes the assessment of longitudinal growth patterns and causality between SES and growth outcomes. Moreso, potential confounding factors such as genetic influences, dietary habits, and physical activity levels were not extensively accounted for, which might have further elucidated the variations in anthropometric dimensions. Finally, the study was geographically confined to a specific region of Nigeria, which may limit its applicability to other regions with different socio-economic and cultural backgrounds.

Recommendations for further research

Future research should adopt a longitudinal design to monitor growth trends over time and establish causal relationships between socio-economic status (SES) and anthropometric outcomes. Incorporating diverse regions within Nigeria will improve the generalizability of findings. Additionally, future studies should use comprehensive SES indicators, such as parental income and education, which will likely provide a deeper understanding of the factors influencing growth. Investigating the roles of diet, genetics, and physical activity as potential confounding factors will also help to complement and enrich the findings. This will inform strategies to promote equitable adolescent growth.

Conclusion

This study assessed the variations in stature and anthropometric limb dimensions of adolescent Nigerian school children, considering sex and socio-economic status (SES) using school type as an indicator. The findings revealed significant differences in anthropometric dimensions between adolescents from public and private schools, reflecting the influence of SES on growth patterns. The private school students involved in this study exhibited consistently higher anthropometric values across all parameters compared to their public school counterparts, underscoring the impact of better access to resources, nutrition, and living conditions associated with higher SES. Sex differences were more pronounced in the public school population, where females exhibited higher values than males—a pattern attributable to the earlier onset of the adolescent growth spurt in females. These findings contribute valuable reference data for growth research, nutrition assessment, and the evaluation of secular trends in adolescent growth patterns in African populations.