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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 13  |  Issue : 1  |  Page : 57-61

Prevalence of elevated blood pressure among primary school children in Kano Metropolis, Nigeria


1 Department of Pediatrics, Rasheed Shekoni Specialist Hospital Dutse, Jigawa State, Kano, Nigeria
2 Department of Pediatrics, Aminu Kano Teaching Department of Pediatrics, Aminu Kano Teaching Hospital, Kano, Nigeria

Date of Web Publication13-Jan-2016

Correspondence Address:
Umar Also
Department of Pediatrics, Rasheed Shekoni Specialist Hospital Dutse, Jigawa State
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0189-7969.165167

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  Abstract 

Background: The high prevalence of hypertension in developing countries has stimulated a lot of research, one of which is tracking of childhood blood pressure (BP). To the authors' knowledge, the point prevalence of elevated BP among primary school children in Kano Metropolis, Kano State, Nigeria has not been documented.
Objective: To determine the BP levels and the point prevalence of elevated BP among primary school children in Kano Metropolis, Nigeria.
Materials and Methods: A multistage sampling technique was used to select 2000 pupils from 66 primary schools in Kano aged 6–14 years. Data were collected using a standardized pretested questionnaires completed by the parents/guardians. BP was measured with a mercury sphygmomanometer. Average of three readings was recorded for each pupil as his/her BP. Weight and height were also recorded using standard techniques. Elevated BP was defined using the criteria by the 4th task force, according to age, gender, and height.
Results: A total of 2000 pupils were studied with 1058 females and 942 boys with a ratio of 1.1:1. The mean systolic blood pressures (SBP) among males and females were 93.17 ± 8.70 and 94.28 ± 9.06 mm Hg while the mean diastolic blood pressures (DBP) were 59.1 ± 6.9 and 60.3 ± 6.9 mm Hg, respectively. Overall, there was a significant positive correlation between SBP (r = 0.44) and DBP (r = 0.38) with body mass index (BMI). Using criteria by the 4th report, 3% of pupils had elevated BP in this study.
Conclusion: There is a positive correlation between SBP/DBP and BMI, the overall prevalence rate of elevated BP among the study population was 3%.

Keywords: Blood pressure, children, Kano


How to cite this article:
Also U, Asani M, Ibrahim M. Prevalence of elevated blood pressure among primary school children in Kano Metropolis, Nigeria. Nig J Cardiol 2016;13:57-61

How to cite this URL:
Also U, Asani M, Ibrahim M. Prevalence of elevated blood pressure among primary school children in Kano Metropolis, Nigeria. Nig J Cardiol [serial online] 2016 [cited 2019 Aug 21];13:57-61. Available from: http://www.nigjcardiol.org/text.asp?2016/13/1/57/165167


  Introduction Top


The 4th report on the diagnosis, evaluation, and treatment of high blood pressure (BP) defined hypertension as average systolic blood pressure (SBP) and/or diastolic blood pressure (DBP) that is, ≥95th percentile for sex, age, and height on three or more occasions.[1] The value of childhood BP measurements in predicting future BP status has been demonstrated in various studies [2],[3] deploying tracking. Tracking is defined as the tendency of subjects to maintain their relative position within the distribution of BP as a function of age.[3] Therefore, measurement of BP in children and young adults is important in the early detection and prevention of adult hypertensive disease.[4] In an attempt to study and prevent the development of hypertension, there is a growing interest in measuring BP in children because the nature of essential hypertension may be more clearly understood if it could be studied early in the course of its natural history.[5]

The prevalence of hypertension varies from one location to another even in the same region, depending on the criteria used for defining hypertension.[6],[7],[8],[9] In Nigeria, Bugaje et al.[8] found a prevalence rate of 3.7% in their study of 2035 adolescents in Zaria. Similarly, Einterz et al.[7] reported a prevalence rate of 3.3% among 904 children in Benue State aged 2–20 years. He also found raised BP to be more predominant among late adolescents. Ujunwa et al.[10] reported a prevalence rate of 5.4% among 2694 adolescents in Enugu. They also reported the highest rate of raised BP among the mid and late adolescents. Asani and Bode-Thomas [11] reported a prevalence rate of 9.52% among 1807 children, aged 6–14 years in Jos metropolis; they also found the prevalence to be higher with increasing age, but Ekunwe and Odujinrin [12] reported a prevalence of 1.8% in Lagos. In another study, Abu-Bakare and Oyaide [9] reported a prevalence rate of 6.8% among 684 secondary school students in Benin. Bello [13] reported a prevalence rate of 14.4% among 404 children in Esie near Ilorin. He also noted that the early adolescents have the highest rate of hypertension. Antia-Obong and Antia-Obong [5] in their study involving urban and rural primary school children in Ibadan described rates of 4.8% and 4.5%, respectively. Ayoola [14] reported a prevalence rate of 3.3% among 487 adolescents aged 11–19 years in Ile-Ife. Similarly, Chiolero et al.[15] reported a prevalence rate of elevated BP of 9.1% and 10.1% among boys and girls, respectively, in Seychelles. They enrolled 18,119 children aged 5–16 years in the study. Mahyar et al.[16] reported prevalence rates of 6.5% and 12.8% for systolic and diastolic high BP, respectively, among 789 primary school children aged 7–12 years in Eghbalieh Iran.

From the foregoing, it is obvious that BP levels and prevalence vary from one location to another; therefore, the present study was designed to determine the BP levels and point prevalence of elevated BP among apparently healthy primary school children in Kano Metropolis, Kano State, Nigeria.


  Materials and Methods Top


The study was conducted in Kano Metropolis, Kano State. Kano is located in the Sudan savannah belt of Nigeria. Kano Metropolis is made up of eight local government areas; namely Tarauni, Dala, Fagge, Gwale, Kano municipal, Nasarawa, Kumbotso, and Ungogo. It has an area of 499 km 2 with a population of 3,628,861, according to 2006 census.[17]

The study design was descriptive and cross-sectional among apparently healthy primary school children aged 6–14 years. The study was carried out over a period of 9 months (February to October 2013). Subjects with generalized body swelling, known diabetics, hypertensive or on drugs that affect BP were excluded from the study.

Institutional approval for the study was obtained from State Primary Education Board. Ethical clearance was also obtained from Medical Research Ethics Committee of Aminu Kano Teaching Hospital. Permission was also obtained from the headmasters of the respective schools. Written informed consent/assent was obtained from parents/guardians of each child.

The 2000 subjects were selected for the study using a multistage sampling technique. Three local governments were selected, and then one public and one private school were selected from each political ward with the help of the lists of the schools from the state ministry of education.[18] 22 schools from Kumbotso, 20 schools from Tarauni while 24 schools from Nasarawa Local Government. Thus, a total of 66 primary schools were selected. A proportionate number was given to each school based on their population.

Initial visits were made to each school and the subjects were familiarized with the objective of the study, the questionnaires, and consent/assent forms were distributed to the pupils for their parents/guardians to fill and give consent for the study.

Data were collected using standard pretested questionnaires filled by the parents/guardians or literate relation or neighbor. Anthropometric measurements were done using rose stadiometer and Weylux weighing scale. Body mass index (BMI) was calculated as weight divided by height squared (kg/m 2). 95th percentile from the gender specific data was taken as “obesity” while 85th percentile to < 95th percentile as “overweight.” BP was measured using mercury sphygmomanometer, according to the 4th report. Cuff sizes of 9 cm × 24 cm and 13 cm × 30 cm were used for those < 12 years and above 12 years old, respectively. Three readings were taken at an interval of 5 min for each pupil and the average was calculated. All equipment were standardized at each enrollment session. The SBP was determined by the onset of the “tapping” Korotkoff sounds (K1), while the disappearance of Korotkoff sounds (fifth Korotkoff sound K5) was the DBP.[19] The classification of BP percentiles for this study was determined using the percentile chart generated from the study subjects. The 95th percentile was used to determine elevated BP for each child's age, gender, and height.[1]

The data were analyzed with the aid of a computer using the Statistical Package for Social Sciences (SPSS) version 16. Mean values and standard deviation of diastolic and systolic pressure were calculated. Correlation coefficients of SBP and DBP with BMI were calculated using a parametric test (Pearson product moment correlation coefficient). Mean gender differences in BMI and BP were compared using z-score. P <0.05 was considered significant.


  Results Top


A total of 2000 pupils were made up of 1058 females (52.90%) and 942 males (47.10%) with a female: male ratio of 1.1:1. The age ranged from 6 years to 14 years with a mean of 10.40 ± 2.40. The mean ages of male and female subjects were 10.60 ± 2.40 and 10.20 ± 2.50, respectively.

Blood pressure levels

[Table 1] shows the mean BP levels according to age and sex. The overall mean SBP was 93.17 ± 8.70 mm Hg for males and 94.28 ± 9.06 mm Hg for females. The difference is statistically significant (z = 2.790, P < 0.05). The SBP shows a gradual increase with age for girls from 85.87 ± 5.81 mm Hg at 6 years to 101.75 ± 9.29 mm Hg at 14 years of age. A similar pattern was observed in boys until the age of 10 and 13 years when a slight declined was observed with subsequent increase thereafter. The overall mean DBP for females is 60.31 ± 6.96 mm Hg, which is higher than the 59.12 ± 6.96 mm Hg for males. The difference is statistically significant (z = 3.831, P < 0.05). The DBP also shows a gradual increase with age for both sexes.
Table 1: BP levels according to age and sex (mean±SD)

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Relationship between blood pressure and body mass index

There was a significant positive correlation between SBP and BMI in girls for ages 9, 10, 12, 13, and 14 years. While in boys only 8, 12, 13, and 14 years of ages show strong positive correlation. The DBP also shows a positive correlation in girls from 9 to 13 years ages, while in boys only 6, 7, and 13 years of ages show positive correlation. Overall, there was a significant positive correlation between SBP (r = 0.44) and DBP (r = 0.38) with BMI. [Table 2] shows the BMI distribution among the study subjects. The gender difference in the mean was statistically significant only in 10 and 11 years of age. The prevalence of obesity and overweight were 3.65% and 9.45%, respectively. Among subjects with elevated BP, 27.86% had obesity/overweight. [Figure 1] shows how SBP rises with increased BMI.
Table 2: Mean±SD of BMI according to age and sex

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Figure 1: Relationship of body mass index with systolic blood pressures in both sexes

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Prevalence rate of elevated blood pressure

Using the criteria proposed by the 4th report on the diagnosis of high BP, 61 (3.05%) of the 2000 subjects were found to have elevated BP. Twenty-three (1.15%) were boys and 38 (1.9%) were girls. Of these, 38 (1.9%) had elevated SBP only, 16 (0.85%) had elevated DBP while in 0.25% both SBP and DBP were elevated. There were more girls (62.3%) than boys (37.7%) with elevated BP. The highest prevalence was seen in 14 and 13 years age categories.


  Discussion Top


The overall mean SBP of 93.8 ± 8.91 mm Hg and the mean DBP of 59.8 ± 6.95 mm Hg were lower than the values reported by Ayoola [14] in Ibadan who reported mean SBP of 106.5 ± 11.8 mm Hg and mean DBP of 61.0 ± 9.0 mm Hg in his subjects. In another study, Ujunwa et al.[10] in Enugu reported higher mean values of SBP and DBP, respectively. The likely explanations are higher mean anthropometric values, involvement of only adolescents by some studies, and environmental variation could explain these higher values.

BMI was found to correlate significantly with SBP and DBP in both sexes in this study. This is in agreement with the study reported by Chiolero et al.[15] who found that both SBP and DBP were strongly associated with BMI in children of the Seychelles. In their study, overweight and obesity accounted for approximately one-fifth of all children with elevated BP, while in this study 27.86% of those with elevated BP were obese and overweight.

In this study, the mean SBP and DBPs were significantly higher in girls than boys. The findings of the present study are similar to those of previous reports from Jos and Zaria.[8],[11] Due to the earlier onset of puberty, higher BMI among girls may possibly explain this gender disparity of BP.

Using the criteria proposed by the 4th report, the prevalence of elevated SBP and DBP obtained in the present study were 1.90% and 0.85%, respectively, while 0.25% of the subjects had both SBP and DBP elevated. The overall prevalence of elevated BP in this study was 3%. This is similar to the finding by Einterz et al.[7] who reported a prevalence of 3.3%, and Bugaje et al.[8] with reported prevalence of 3.7%, and Ayoola [14] with reported prevalence of 3.3%. The prevalence is low when compared to that reported by Asani and Bode-Thomas [11] and Ujunwa et al.[10] who reported a prevalence of 9.52% and 5.8%, respectively. This difference in the prevalence could be explained by different criteria used for defining hypertension. Similarly, Chiolero et al.[15] reported a higher prevalence in Seychelles. The use of the automated device, high prevalence of overweight/obesity, use of US reference tables to define high BP could explain some of this difference. The prevalence of hypertension in the present study is higher than that reported by Ekunwe and Odujinrin [12] in Lagos, with a reported prevalence of 1.87%. The use of 97th percentile for defining high BP could account for this lower value.

The present study found a higher prevalence of elevated BP in older age groups. This is similar to the finding by Mahyar et al.[16] and Einterz et al.[7] from Benue. It contrasts with the finding of Chiolero et al.[15] where higher prevalence was reported among younger children. The possible explanations included a larger reaction alert, measurement bias with the automated device (smaller vs. larger arms), and use of American reference value for defining elevated BP.

Prevalence rate of systolic high BP was common among males in this study. This contrasts with the finding of Mahyar et al.[16] where it was common among females while Bugaje et al.[8] did not found significant sex-related differences in the prevalence of systolic high BP. Diastolic high BP in this study was common among females. This agrees with findings of Bugaje et al.,[8] Ekunwe and Odujinrin,[12] and Mahyar et al.[16] The reason why systolic high BP was common among males while diastolic high BP was common among females could be a topic of future research.

Follow-up period was short; ideally, they should have been on follow-up for longer period, especially those with elevated BP to determine if and when any develop hypertension and also detect early end organ damage. Financial and time constraints otherwise sample size should have been > 2000 to establish a nomogram.

Based on the findings of this study, the following conclusions were made: There is a positive correlation between SBP/DBP and BMI. Based on the criteria of the 4th report on the diagnosis, evaluation and treatment of high BP, the prevalence of elevated BP among primary school children in Kano Metropolis was 3%. It is recommended that School health program should be strengthened, and the BP of school children should be routinely measured for the early detection of those with elevated BP and intervention and follow-up.

All children with persistently elevated BPs were subsequently referred to the pediatric cardiology unit of Aminu Kano Teaching Hospital for a full evaluation.

Acknowledgment

We wish to thank the parents and their children for participation in the study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents. Pediatrics 2004;114 2 Suppl: 555-76.  Back to cited text no. 1
    
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Berenson GS, Cresanta JL, Webber LS. High blood pressure in the young. Annu Rev Med 1984;35:535-60.  Back to cited text no. 2
    
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De Swiet M, Fayers P, Shinebourne EA. Value of repeated blood pressure measurements in children – The Brompton study. Br Med J 1980;280:1567-9.  Back to cited text no. 3
    
4.
Shear CL, Burke GL, Freedman DS, Berenson GS. Value of childhood blood pressure measurements and family history in predicting future blood pressure status: Results from 8 years of follow-up in the Bogalusa Heart Study. Pediatrics 1986;77:862-9.  Back to cited text no. 4
    
5.
Antia-Obong OE, Antia-Obong LE. Arterial blood pressure of Nigerian urban- rural school children. Niger J Paediatr 1991;18:3-11.  Back to cited text no. 5
    
6.
Abdurrahman MB, Babaoye FA, Narayana P. Childhood hypertension in Northern Nigeria. West Afr J Med 1982;4:7-11.  Back to cited text no. 6
    
7.
Einterz EM, Hutchinson T, Flegel K. Survey of blood pressure in Nigerian children. Trop Doct 1982;12:172-5.  Back to cited text no. 7
    
8.
Bugaje MA, Yakubu AM, Ogala WN. Prevalence of adolescent hypertension in Zaria. Niger J Paediatr 2005;32:77-82.  Back to cited text no. 8
    
9.
Abu-Bakare A, Oyaide SM. Blood pressure levels in Nigerian school girls. J Trop Pediatr 1983;29:225-9.  Back to cited text no. 9
    
10.
Ujunwa FA, Ikefuna AN, Nwokocha AR, Chinawa JM. Hypertension and prehypertension among adolescents in secondary schools in Enugu, South East Nigeria. Ital J Pediatr 2013;39:70.  Back to cited text no. 10
    
11.
Asani MO, Bode-Thomas F. Blood pressure pattern and its correlates among primary school children in Jos Nigeria. Highland Med Res Ltd 2005;3:29-35.  Back to cited text no. 11
    
12.
Ekunwe O, Odujinrin OM. Proteinuria and blood pressure profile of Lagos school children. Niger J Paediatr 1989;16:15-22.  Back to cited text no. 12
    
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Bello AB. Hypertension among Nigerian children. Niger Med J 1993;25:71-5.  Back to cited text no. 13
    
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Ayoola EA. Prevalence of adolescent hypertension in Nigeria. Niger J Paediatr 1979;6:18-26.  Back to cited text no. 14
    
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Chiolero A, Madeleine G, Gabriel A, Burnier M, Paccaud F, Bovet P. Prevalence of elevated blood pressure and association with overweight in children of a rapidly developing country. J Hum Hypertens 2007;21:120-7.  Back to cited text no. 15
    
16.
Mahyar A, Ebrahemi M, Shahsavari A, Rahmani Y. Blood pressure of primary-school children of Eghbalieh city, Islamic Republic of Iran. East Mediterr Health J 2009;15:1449-54.  Back to cited text no. 16
    
17.
Kano State. Available from: . [Last cited on 2011 Jan 11].  Back to cited text no. 17
    
18.
Ministry of Education Kano State Annual Schools Census Results 2009-2010. June, 2010. p. 6-12.  Back to cited text no. 18
    
19.
Lewington S, Clarke R, Qizilbash N, Peto R, Collins R, Prospective Studies Collaboration. Age-specific relevance of usual blood pressure to vascular mortality: A meta-analysis of individual data for one million adults in 61 prospective studies. Lancet 2002;360:1903-13.  Back to cited text no. 19
    


    Figures

  [Figure 1]
 
 
    Tables

  [Table 1], [Table 2]


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