|Year : 2014 | Volume
| Issue : 1 | Page : 24-29
Prevalence of thinness among adolescents in Kano, Northwestern Nigeria
Muhammad S Mijinyawa, Shehu M Yusuf, Ibrahim D Gezawa, Baba M Musa, Andrew E Uloko
Department of Medicine, Bayero University, Aminu Kano Teaching Hospital, Kano, Nigeria
|Date of Web Publication||7-Apr-2014|
Ibrahim D Gezawa
Department of Medicine, Aminu Kano Teaching Hospital, 3452 Kano
Source of Support: None, Conflict of Interest: None
Background: Thinness in older children has been associated with delayed pubertal maturation, reduced muscular strength and work capacity. There is paucity of studies on thinness among adolescents in Nigeria. Objectives: The aim of this study was to determine the prevalence of thinness among adolescents in Kano, Northwestern Nigeria . Materials and Methods: In this descriptive cross-sectional survey, we used a multi-staged random sampling technique to select 718 students from six secondary schools in Kano metropolis. A pretested questionnaire was used to collect socio-demographic data. Physical measurements for weight and height were carried out using standard procedures. Results: The overall prevalence of thinness was 60.6%, with a higher prevalence among boys (63.0%) compared with girls (58.7%). Grades-I, II and III thinness were found in 26.0%, 15.5% and 19.1% of the studied subjects respectively. The prevalence of grade III thinness was higher among boys (19.4%) compared with girls (18.8%). The rate of thinness was observed to increase with age up to 16 years after which it starts to fall. Older age was also found to be independently associated with thinness among our subjects. Conclusion: The prevalence of thinness among adolescents in Kano is high, with a slightly higher rate in boys than girls. There is need for concerted effort by policy makers to come up with programmes aimed at reducing the burden of undernutrition among school children in our setting.
Keywords: Adolescents, Kano, Nigeria, prevalence, thinness
|How to cite this article:|
Mijinyawa MS, Yusuf SM, Gezawa ID, Musa BM, Uloko AE. Prevalence of thinness among adolescents in Kano, Northwestern Nigeria. Niger J Basic Clin Sci 2014;11:24-9
|How to cite this URL:|
Mijinyawa MS, Yusuf SM, Gezawa ID, Musa BM, Uloko AE. Prevalence of thinness among adolescents in Kano, Northwestern Nigeria. Niger J Basic Clin Sci [serial online] 2014 [cited 2019 Mar 20];11:24-9. Available from: http://www.njbcs.net/text.asp?2014/11/1/24/130165
| Introduction|| |
Adolescence is the period of physical, psychological and social maturation from childhood to adulthood. During adolescence, 20% of final adult height and 50% of adult weight are attained, bone mass increases of 45% and dramatic bone remodelling occur while soft tissues, organs and even red blood cell mass increase in size.  An estimated 20% of the total world population are adolescents. The adolescent population in developing countries is much higher compared to developed countries as reflected in Salvador where they constitute 26% of the population compared to the USA's 14% adolescent population.  Data from the United Nations indicates that as at 1995, total adolescent population from the developing world stood at 914 million with a projected rise to 1.13 billion by the year 2025.  With improving maternal and child health in recent years, Africa is likely to experience an adolescent population growth that will rapidly surpass those of Asia and Latin America.
Over the years, the presumption that adolescents are less susceptible to disease and suffer relatively fewer life-threatening conditions has limited research interest in this group. Furthermore, adolescent health needs are not adequately met resulting in huge social and economic issues to their immediate families and the general population. Yet, it is common knowledge that adolescents constitute a significant population that shapes the future of any nation economically since they represent a huge potential work force and future leaders. Adolescent health thus becomes very relevant in determining the social and economic life of any nation.
The nutritional status of adolescents contributes significantly to the health status of the community in which they reside. One of the major global health problems faced by developing countries today is undernutrition.  Thinness can be a marker of undernutrition although thin children are not necessarily undernourished. The considerable amount of epidemiological data on child and adolescent obesity is in contrast to the paucity of data regarding the prevalence of thinness or underweight among adolescents. One of the reasons given for the lack of information has been the difficulty of interpreting anthropometric data in these age groups.  The Body-Mass-Index -for-age (BMI-for-age) reference has since been recognised as the tool of choice for screening and monitoring of the nutritional status of adolescents.  However, until recently there were no suitable thinness cut-offs for 6-18-year age group, making comparisons of prevalence rates of thinness between surveys difficult.  Based on an international survey published by Cole et al.,  thinness defined as low BMI for age, was graded into mild- I, moderate-II and severe-III. There is dearth of studies on the prevalence of thinness among adolescents in Nigeria. To our knowledge, no such study has been carried out in Kano, located in the northwestern part of the country. We, therefore, set out to determine the prevalence of thinness among adolescents in Kano, northwestern Nigeria.
| Materials and Methods|| |
The study was carried out in Kano, the Capital city of Kano State in Northwest Nigeria, located between latitude 12° 00' North and longitude 8° 13'East. It occupies a total area of 499 square kilometres with an estimated population of 2,828,861 (2006 census).  Approximately 35% of the population are literate with high gender disparities in school attendance and literacy.  For example, at primary school level, the gross enrolment rate for boys is 81.3% compared to 65.5% for girls. At secondary school level, the disparity improves slightly but overall gross enrolment rates are much lower at 45.9%, compared to 73.7% at primary school level. 
The principal inhabitants of the city are the Hausa-Fulanis, although a good number of other ethnic groups, such as the Igbos and Yorubas also inhabit parts of the city. The major language spoken is Hausa, although English is also widely spoken in schools, offices and markets. Kano is acclaimed to be Nigeria's centre of commerce with its economic significance dating back to the pre-colonial era when it served as the southernmost point of the famous trans-Sahara trade routes. A sizeable number of its inhabitants are engaged in farming, some are civil servants while the rest are largely traders.
A cross-sectional survey was carried out to determine the prevalence of thinness among adolescents (boys and girls) aged 13-18 years attending secondary schools in Kano metropolis. Both private and government-owned schools were selected in order to have a fair representation from the different social strata of the society. All the students whose parents or guardians consented were studied. The students whose parents did not consent and those that have a chronic illness as well as non-Nigerians were excluded. Similarly those above 19 years and those below 13 were not recruited for the study.
Sample size determination
All students of the chosen schools within the study age group were considered. However, in each school, systematic sampling method was employed in which the students were given numbers serially according to their classroom register from JSS 1 to SS3, thereby, giving each student an equal chance. The random number table was used to select the first study subject and thereafter students were picked at regular interval (sample interval) so as to meet the sample size requirement in the school. This sample interval (SI) was determined by dividing the total number of students in the selected schools by the sample size: 9,758/1000 = 9.758 = 10.
A comprehensive list of all the secondary schools in Kano was collected from the State Ministry of Education. The schools for the study were then selected with the use of simple random sampling technique applied through the use of a table of random numbers. A Multistage sampling technique was used in selecting the study subjects. From the comprehensive list of schools obtained from the ministry of Education, five schools for males and five for females were selected using simple random technique in the initial stage. Subsequently, the number of subjects to be studied in the sampled schools was obtained based on the proportionate size of the schools. Thereafter, the class room registers were used as the sampling frames. Systematic sampling method was then used to select the subjects from each class.
Ethical approval for the study was obtained from the ethics committee of Aminu Kano Teaching Hospital, Kano. Permission was obtained from the local education authority and the Principals of the selected schools. Informed consent was also sought obtained from each participant's parent/guardian before being enrolled.
A pretested questionnaire was used to collect socio-demographic data from the respondents. The questionnaire inquired about socio-demographic characteristics, current and past medical illness and some information on eating habit. Results of basic anthropometric measurements for each participant were also recorded in the questionnaire.
Anthropometric measurements and assessment of thinness
The weight of each student was measured, with the student bare footed and with light clothing, using WEYLUX weighing scale. Their height was measured using ACCUSTAT Ross stadiometer. The students were asked to stand erect with the heels, buttocks, upper back and occiput against the stadiometer and with their caps or head ties removed. The measurements were recorded to the nearest 1 cm. The BMI was then computed using the standard formula [BMI = weight (kg)/height (m 2 )]. Thinness was defined as low BMI for age and was graded into III, II, and I (severe, moderate and mild), respectively, corresponding with BMI values of 16.0, 17.0 and 18.5 kg/m 2 , respectively, as proposed by Cole et al.,  and was derived from International Surveys (IS) based on nationally representative samples of children aged 6-18 years collected between 1963 and 1993 in the United States, Brazil, Great Britain, Hong Kong, the Netherlands and Singapore. The uses of these cut-off points were suggested to encourage direct comparison of trends in childhood thinness and overweight/obesity worldwide and have been recommended by the International Obesity Task Force (IOTF). All measurements were carried out by trained assistants and the weighing scale was assessed for proper calibration each morning before it was used.
All data obtained were analysed using statistical STATA version 11. Quantitative variables were expressed as mean (SD), while qualitative variables were expressed as number and (percentage). Student's t-tests were used to assess the significance of differences in means between the sexes at each age group. Differences in qualitative variables between groups were determined using Chi-square test. Multivariate logistic regression analysis was used to quantify the independent predictors of thinness with odds ratio and 95% CI obtained. Statistical significance was set at P < 0.05.
| Results|| |
Of the 1000 students recruited for the study, only 718 students eventually participated in the study, out of which 57% were females and 43% were males. The median age was 16 years with a range of 13-19 years. The median height was 1.57 meters, with a range of 1.20-1.88 meters while the median weight was 45 kg with a range of 24-120 kg. The median BMI was 17.86 kg/m 2 with a range of 11.31-42.97 kg/m 2 . As shown in [Table 1], all the anthropometric indices showed a sustained increase with age in both genders, with the girls being statistically significantly heavier and taller than the boys in the 13 year age group, P values 0.02 and 0.01, respectively, while in the 16 and 17-year age group, the boys were significantly heavier and taller than the females, P values 0.01 and 0.001, respectively. At the age of 18 the boys were also found to be taller than the females, P value 0.001.
The differences in the mean BMI between the sexes across all age groups were, however, not statistically significant. The overall prevalence of thinness was 60.6%, 95% C.I. (56.81-64.11) with grades-I, II and III thinness constituting 26.0%, 15.5% and 19.1%, respectively. The overall prevalence was higher (63.0%) among boys than girls (58.7%). While the prevalence of grade III thinness was found to be slightly higher among boys compared with girls (19.4% vs. 18.8), the girls had higher prevalence of grade II thinness when compared with the boys (16.4 vs. 14.2), the differences were, however, not statistically significant (P = 0.361). Analysis by age group showed that the prevalence of thinness increased with age up to 16 years followed by a decrease. Overall, the highest prevalence of thinness (93.5%) was found in the 13-year age group, while the lowest prevalence (30.4%) was observed in the 18-year age group.
[Table 2] depicts the prevalence of thinness among boys and girls, respectively, by age group.
|Table 2: Prevalence of thinness among the study subjects by age and gender|
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As shown in the Table, the prevalence of grade III thinness was highest among boys in the 13-15-year age group compared with girls in whom the prevalence of grade III thinness was higher than that in boys in the 16-18-year age group. In all the age groups, except the 17-year age group, the prevalence of grade II thinness was higher among girls compared with boys. Grade I thinness was more common among boys in the 13-18-year age group.
In multivariate logistic regression analysis adjusted simultaneously for age, sex and social status, older age was found to have a significant independent association with thinness as shown in [Table 3].
| Discussion|| |
Undernutrition among children and adolescents constitutes a serious public health problem in developing countries.  Cole et al., in a recent study, stated that undernutrition is better assessed asthinness (low BMI for age) than wasting (low weight for height). Although thinness, just like stunting and wasting, is known to lead to delayed mental development, reduced intellectual capacity, poor educational achievement, and higher morbidity and mortality rates,  its prevalence has largely been underreported in our setting. The overall prevalence of thinness in our study was 60.6%. This figure is higher than the 32.8% reported by Ejike et al., among adolescents in Umuahia, Southeastern Nigeria, but lower than the 87.2% reported by Goon et al.,  from Makurdi in north-central Nigeria. While the reported prevalence of thinness from the former study was based on the IS BMI cut-off points as in our study, in the latter survey the World Health Organization (WHO) growth reference was employed. The IS standard has been reported to under-diagnose thinness (especially grades I and II) relative to the WHO reference standard.  The difference in cut-off points used may explain the higher prevalence of thinness found in the Makurdi study. The higher prevalence of thinness in boys compared with girls demonstrated in our study is in keeping with an earlier report from southeastern Nigeria.  Other studies have reported equal prevalence rates of thinness in both genders. ,, A study from Portugal however, found a higher prevalence of thinness among girls than boys using the same cut-off point as in our study.  The fact that using different cut-off points leads to considerable differences in the prevalence of thinness and also changes the relationships between genders stresses the need for further research in order to provide reliable, internationally agreed values to define thinness and/or undernutrition.
The prevalence of grade III (severe) thinness in our study was found to be slightly higher in boys compared with girls (19.4% vs. 18.8%). This observation corroborates that of Fetuga et al., who also reported the prevalence of grade III thinness to be higher in boys than in girls among their subjects. A plausible explanation for this finding is that in our setting, boys tend to engage in more physically demanding activities than girls, including walking to school daily irrespective of the distance and partaking in rigorous sporting activities. Previous studies have reported higher levels of physical activity in children associated with active travel to school. , The increased physical activity and by extension energy expenditure, may explain why the boys in our study were found to be thinner. The prevalence of thinness increased with age in our subjects up to the age of 15 years and decreased thereafter. Similar trend in the prevalence of thinness was also reported by Fetuga et al., in southwestern Nigeria and Marques-Vidal et al., among European adolescents. Rao et al., (India) and Sahabuddin et al., (Bangladesh) on their part reported decreased prevalence of thinness with age. Possible explanations for the increased prevalence of thinness with age include morphological changes during puberty in boys  and increased physical activity.  In addition, increased restrictive eating behaviours with age may be an explanation among girls.  On multivariate logistic regression analysis, older age was found to be independently associated with thinness among our subjects. The main strength of our study is that we established the prevalence of thinness in a representative sample of adolescents attending secondary schools in our setting, using well trained assistants who undertook all anthropometric measurements under close supervision.
| Conclusions|| |
We appreciate the fact that our study has a number of limitations. The cut-off points used to define thinness in this study was derived based on arbitrarily set BMI values which reflect changes in BMI that occur with age in children outside the African continent. Ethnic-specific BMI cut-off points would have been more appropriate for defining thinness in our study population. Data on the socioeconomic status of our subjects were not detailed enough. This may explain the lack of association between social status and thinness in our study. Finally, we did not explore the dietary habit/eating pattern of our subjects which may greatly influence the distribution of thinness in our study population. Despite these limitations, this study has provided new data on the prevalence of thinness among school going adolescents in Kano that were hitherto unavailable. Furthermore, considering the fact that the sociodemographic characteristics of most urban cities in Northern Nigeria are similar, the results of this study can be generalized to school going adolescent populations in other cities in the region.
Finally, the prevalence of thinness among adolescents attending secondary schools in Kano, Nigeria, was high. There is need for concerted effort by the government and other stakeholders in the education sector to come up with nutritional intervention programmes aimed at reducing the burden of undernutrition among school going adolescents in our setting. Further studies are needed to establish the influence of parental socioeconomic status on the prevalence of thinness among this subset of adolescents in Kano, Nigeria.
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[Table 1], [Table 2], [Table 3]