Niger J Paed 2014; 41 (3):223 –228  
Sadoh WE  
Omuemu VO  
Sadoh AE  
Iduoriyekemwen NJ  
Nwaneri UD  
Adigweme IN  
Owobo AC  
Blood pressure percentiles in a  
group of Nigerian school age  
Uduebor JO  
Ekpebe PA  
Accepted: 6th April 2014  
Abstract: Background: Determi-  
nation of abnormal blood pressure  
BP) in children is dependent on  
comparison with normal percentile  
values. The commonly used Na-  
tional Institute of Health (NIH)  
standard is generated from children  
outside of Africa.  
readings were taken. Hypertension  
was defined asthsystolic and or dia-  
stolic BP >95 percentile of the  
study population.  
Sadoh WE  
Sadoh AE, Iduoriyekemwen NJ,  
Adigweme IN, Uduebor JO, Ekpebe PA  
Nwaneri UD  
Results: There were 1549 subjects,  
aged 5 to 15 years, of which 757  
(48.9%) were males. Prevalence of  
hypertension was 2.6%. Only age  
and weight were independent pre-  
dictors of both elevated systolic  
Department of Child Health,  
Omuemu VO  
Department of Community Health  
University of Benin Teaching Hospital,  
PMB 1111, Benin City, Nigeria.  
Email: sadohehi@yahoo.com  
Objective: To develop BP percen-  
tile values for Nigerian children  
based on BP cuff width 40% to  
and diastolic BP. The 5 , 10 , 50 ,  
0% of arm circumference.  
90 and 95 percentiles of Systolic  
and diastolic BP were generated  
for both males and females pupils.  
Conclusion: BP Percentiles have  
been generated using BP cuff  
width 40 to 50% of the arm cir-  
cumference for Nigerian children.  
Methods: Subjects were pupils  
from nine primary schools in Mid-  
western Nigeria recruited using a  
multi-stage sampling technique.  
Their BP was measured using a  
cuff width of 40 to 50% of arm  
circumference and cuff length of at  
least 80% of arm circumference  
respectively. The mean of two BP  
Owobo AC  
Department of Paediatrics,  
Irrua specialist Teaching Hospital,  
Irrua, Nigeria  
Keyword: Blood pressure; hyper-  
tension; childhood; percentile  
and management.  
Childhood blood pressure (BP) is an important clinical  
parameter of the wellbeing of the child thus, it is impor-  
tant to routinely measure BP of children in clinical set-  
Hypertension in children according to the Fourth Task-  
force on hypertension in children and adolescents is  
defined as elevated systolic blood pressure (SBP) and or  
tings . Childhood BP has been shown by several work-  
diastolic blood pressure (DBP) > 95 percentile for the  
ers to be strongly correlated with weight, hei-g4ht, body  
age and sex. Childhood hypertension is mostly secon-  
dary to underlying conditions while a smaller proportion  
mass index and other anthropometric indices . Higher  
BP has also been demonstrated in male compared to  
is reported to be primary or essential hypertension .  
female children in previous works . This has largely  
been related to the weight of the boys being higher than  
that of the girls. Some workers have shown higher BP in  
urban children compared to the rural children as well as  
differences in blood pressure based on socioeconomic  
Childhood essential hypertension is on the rise globally ,  
it is reported to be associated with family history of es-  
sential hypertension and childhood overweight/ obe-  
sity . Decreased physical activity, increase in sedentary  
life style including watching television and the large  
consumption of the fattening fast food are found to be  
classes in adolescent girls .  
contributors to childhood hypertension .  
It is important to measure BP in children and identify  
those with elevated BP because BP tracks from child-  
hood to adulthood . Children with elevated BP tend to  
continue to have high BP into adulthood. Thus identifi-  
cation of these individuals is important for follow up  
The increasing recognition of these facts should per-  
suade health care worker as to the need to routinely  
measure the BP of children as they present in clinical  
and other settings. It is also important to be able to  
interpret the measured BP. Interpretation of measured  
BP is usually based on comparison of the measured  
value with what is considered normal or standard values.  
The BP standards generated by NIH and the Nation1,a12l  
High Blood Pressure Education Program (NHBPEP)  
from data obtained from Caucasian, African American,  
latino and Asian children would seem ideal for most  
children globally and it is currently being used. How-  
ever negroid children from Africa were not included in  
the data base. The African American children may not  
adequately represent the African children since they may  
be exposed to different stressors as their environments  
are different. In addition, the method of measuring BP  
from which the NIH BP standards were derived is  
flawed. Cuff specification that include bladder width  
that is 40 - 50% of mid arm circumference and bladder  
length that is 80 100% of the mid arm circumference  
will produce a more accurate measurement of BP than  
the previous specification that included the cuff width of  
19 private schools in the three selected wards from  
which 30% each of private and public schools were se-  
lected from a list of alphabetically arranged schools.  
Thus, three public and six private schools were selected  
using a systematic sampling technique after randomly  
selecting the first school (second stage). The school  
sample size was determined as the ratio of the product of  
index school population and study sample size (1549)  
over the pooled population of the nine selected schools.  
The school sample size was thus determined in propor-  
tion to school population. A systematic sampling  
method was employed to select pupils from each school.  
Evaluation of selected pupils  
An informed written consent was obtained from the par-  
ents of each selected pupil. Any child whose parent de-  
clined to give consent was replaced by the next pupil on  
the sampling list selected using the sampling interval  
and whose parent gave consent. A socioeconomic class  
was ascribed to each selected pupil using the method  
/3 or 3/4 of the arm’s length, the specification with  
which the NIH standards were derived . The cuff speci-  
fication has been corrected by the steering committee of  
America Heart association (AHA) in recommending  
cuff size that included bladder width and length that is  
described by Olusanya et al . The selected pupil then  
had a thorough general and systemic examination with  
emphasis on the cardiovascular system. The weight was  
measured with the shoes, wrist watches, belts and other  
thick clothing taken off and the subject was in his or her  
school uniform only. The Omron body composition  
monitor (BF511Netherlands) was employed to measure  
the weight. The pupils were instructed to stand erect and  
looking straight ahead on the weighing machine. The  
weight once captured was displayed on the machine.  
The weight was read to the nearest 0.1 kg. The height  
was taken with the aid of a stadiometer with the pupils’  
shoes and stockings off, the pupils were instructed to  
stand against the stadiometer with the heels, buttocks  
and occiput resting against the stadiometer. The chin  
was raised so that the subject was looking ahead with  
the upper border of the ear canal in the same horizontal  
plane as the lower border of their eye socket (Frankfurt  
plane). The height was read to the nearest 0.1 cm. The  
Body Mass Index (BMI) for age was then computed for  
the pupils as the ratio of the weight in kg/ square of the  
cumference for children, in 1988 .This specification  
0 - 50% and 80 – 100% respectively of mid arm cir-  
was also recommended by the 1996 update of4the Task  
Force on Blood Pressure Control in Children and the  
NHBPEP . Previous Nigerian studies on childhood  
hypertension have relied on the NIH standards which are  
now considered flawed. This indicates the need for ap-  
propriate standards.  
In this study, we set out to determine the BP pattern of a  
population of Nigerian primary school pupils aged 5 –  
5 years and derive BP percentiles based on the new  
cuff specification.  
Subjects and Methods  
This cross sectional study was conducted in Egor Local  
Government Area (LGA), of Edo state of Nigeria as part  
of a larger study to evaluate cardiovascular risks in chil-  
dren. The LGA has an estimated total population of  
height in metres (m ).  
The blood pressure was measured in the right upper arm,  
except where there was an injury to the arm (one pupil).  
The pupils were made to sit down and relax for about 3  
39,899 of which 119,038 are aged less than 15 years .  
It is predominantly urban with ten political wards of  
which two are rural. This study was conducted over a  
six months period (September 2011 to February 2012).  
This period included the times the schools were in ses-  
sion. Ethical approval for this study was obtained from  
the Ethics Committee of the University of Benin Teach-  
ing Hospital, Benin City.  
minutes before the BP was measured. An appropriate  
sized cuff, with bladder width of about 40 - 50% of the  
arm circumference and the bladder length of at least  
80% of the arm circumference was utilised . The cuff  
was smugly applied to the right upper arm and the cuff  
inflated to about 10 mmHg above the systolic BP by  
palpation. The bell of the stethoscope was then applied  
over the brachial artery as the cuff was slowly deflated  
Sampling technique  
at a rate of 2mm per second . The first Korotkov sound  
was taken as the systolic BP while the fifth Korotkov  
sound represented the diastolic BP. Two BP readings  
were taken three minutes apart and the average was  
taken as the patient’s BP. Hthypertension was defined as  
elevated SBP or DBP >95 percentile for the age and  
sex of the percentiles derived in this study.  
One thousand, five hundred and forty nine pupils were  
selected using a multi stage sampling technique. Of the  
0 political wards, 30% (3) of the wards were randomly  
selected from a list of the political wards as the first  
stage of the sampling process . There were 8 public and  
Statistical analysis  
Blood pressure of the study population  
The data was entered into SPSS version 16 (Chicago IL)  
spread sheet and analysis done with the same tool. The  
prevalence of elevated blood pressure was presented in  
percentage. Differences in means of systolic and  
diastolic blood pressures were compared using student’s  
t test. More than two means were compared using  
one-way ANOVA with Turkey-Kramer post hoc test  
when significant. Correlation between two continuous  
variables was tested using Pearson’s correlation test.  
Multiple logistic models were made for predictors of  
elevated systolic and diastolic BP. Level of significance  
was set at p = <0.05.  
Table 3 shows the mean systolic blood pressure (MSBP)  
and mean diastolic blood pressure (MDBP) by gender of  
the pupils and by age. The MSBP of the male pupils  
rose with age from 92.1 ± 6.1 mmHg for the 5 year old  
to 113.1 ± 7.4 mmHg for the 15 year old. The difference  
in MSBP of the youngest and the oldest was statistically  
significant, p = <0.0001. Similarly, the MSBP of the  
females rose with age from 91.5 ± 11.2 mmHg in the  
five year olds to 119.0 ± 10.2 mmHg in the 15 year olds.  
The difference in MSBP between the youngest and old-  
est was significant, p = <0.0001. The Mean diastolic  
blood pressure (MDBP) of the males rose with age from  
9.0 ± 9.2 mmHg at 5 year to 73.9 ± 10.4 mmHg in the  
5 year old. The difference in MDBP of the youngest  
and oldest was significant, P = 0.0001. The females  
similarly showed a rise in MDBP with age, the differ-  
ence was significant, P = 0.001.  
Characteristics of the study population  
There were 1549 primary school pupils who were re-  
cruited for the study. They consisted of 757(48.9%)  
males and 792 (51.1%) females. The age range was 5  
to15 years with a mean age of 8.8 ± 2.2 years. The mean  
age of the female pupils 8.8 ± 2.2 years was not signifi-  
cantly lower than the male pupils 9.1 ± 2.2 years, p  
There were 41pupils with elevated SBP and / DBP  
values >95 percentile for age and sex. The prevalence  
of hypertension was thus 2.6%. Of the 41 pupils, 20  
(48.78%) were female and 21(51.22%) males. The  
prevalence of hypertension among the male and female  
pupils were 20/792(2.5%) and 21/757(2.7%)  
0.092. There were 850(54.9%) and 699(45.1%) pupils  
from the public and private schools respectively. 1510  
pupils had information to compute their SEC. Of the  
Table 3: The gender 5 , 10 , 25 , 50 , 75 , 90 and 95  
height percentiles of the study population  
Age th Mathle Perthcentilthes (inthcm)  
510 pupils, most 740(49%) were in the low SEC. The  
Ftehmale Pthercentthile (thin cm)  
5 10 25 50 75 90 95  
characteristics of the study population are shown in  
table 1.  
25 50 75  
90 95  
109 110 111 115 119 125 127 110 111 114 116 118 121 126  
107 112 116 120 123 128 130 110 112 115 120 125 128 130  
113 115 120 126 130 134 136 113 116 119 123 128 133 138  
116 119 122 127 135 141 143 116 118 122 127 133 138 140  
118 120 125 130 137 142 144 118 121 124 130 136 143 144  
118 120 127 133 139 142 145 120 124 128 134 139 144 149  
Table 1:The characteristics of the study population  
Type of school  
11 121 125 130 134 140 144 146 124 126 131 136 142 147 151  
12 124 127 131 136 143 147 149 126 128 133 137 147 152 157  
125 128 134 141 146 151 153 133 137 140 143 152 157 159  
135 136 136 143 147 152 157 137 140 143 146 153 161 163  
132 133 139 151 152 155 159 140 142 145 149 154 164 167  
yr = years; cm = centimeters  
Socioeconomic class  
The 5 , 10 , 50 , 90 and 95 percentiles of the SBP  
and DBP of the pupils according to age and gender are  
shown in figures 1, 2, 3 and 4. The age, weight, height,  
BMI were positively correlated with the SBP r = 0.32; P  
The height percentiles of the study population  
0.0001, r = 0.4; P = 0.0001, r = 0.36; P = 0.0001 and r  
= 0.3; P = 0.0001 respectively. Multiple linear regres-  
sions models showed that only age and weight were  
independent predictors of elevated SBP; P = 0.0001 and  
Table 2 shows the male and female 5 , 10 , 25 , 50 ,  
th th th  
5 , 90 , and 95 height percentiles of the study popu-  
.013 respectively. (Table 4) Similarly only age and  
weight were independent predictors of elevated DBP; P  
0.01 and 0.006 respectively. (Table 5) The age,  
Table 2: The mean weight of the pupils by age and gender  
year) Weight (Kg) Weight (Kg) P values Height (cm) Height (cm) P value  
weight, height and BMI were positively correlated with  
DBP r = 0.29; P = 0.002, r = 0.36; P = 0.0001, r = 0.030  
and P = 0.0001, r = 0.26; P = 0.0001 respectively.  
20.1 ± 2.3  
22.1 ± 5.2  
24.1 ± 5.2  
25.4 ± 4.7  
30.4 ± 8.4  
31.8 ± 7.3  
34.1 ± 8.3  
36.5 ± 6.3  
41.7 ± 7.8  
42.3 ± 4.7  
49.9 ± 1.1  
19.9 ± 3.0  
22.0 ± 4.3  
25.4 ± 6.4  
27.3 ± 6.7  
29.1 ± 6.1  
30.6 ± 7.9  
31.0 ± 5.3  
32.3 ± 5.6  
36.0 ± 6.6  
36.6 ± 2.2  
41.6 ± 8.5  
116.2 4.0  
120.7 6.2  
124.6 7.9  
115.7 4.9  
119.7 6.9  
126.7 6.9  
127.2 12.7 129.6 8.0  
131.2 8.4  
134.1 8.4  
136.7 7.8  
139.7 9.6  
146.4 7.8  
147.8 6.0  
150.5 5.2  
131.3 8.7  
132.1 8.5  
133.6 7.1  
136.6 7.7 0.04  
142.2 9.8  
142.9 5.6  
149.8 11.5 0.89  
Table 4: Multiple linear regression model showing independ-  
ent predictors of elevated systolic blood pressure  
Variable Beta Std Error t value P value Confidence Interval  
The BP percentile generated in this study was from BP  
values obtained as the means of at least two BP readings  
using an appropriate cuff based on the circumference of  
the arm rather than the length of the a1rm as recom-  
mended by the working Group, NHBPEP .  
Constant 65.15 9.2  
7.09 0.0001 47.10 83.20  
3.68 0.0001 0.27 0.9  
0.59 0.16  
0.39 0.16  
2.74 0.013  
0.08 – 0.70  
-0.05 – 0.23  
-0.39 – 0.76  
0.09 0.071 1.22 0.22  
0.18 0.30 0.63 0.53  
The percentile values generated in this study were based  
on only the age of the child which makes it easy to use  
in a busy paediatric clinic. The NIH percentiles which is  
based on age and the height percentiles of the children is  
rather difficult to use, besides in the San Anthonio blood  
pressure study, it was shown that the contribution of  
height to BP is negligible when weight and age are con-  
trolled for. Thus the rationale for the inclusion of height  
Table 5: Multiple linear regression model showing  
independent predictors of elevated diastolic blood pressure  
Variable Beta Std Error t  
P value Confidence Interval  
Constant 46.7 7.61 6.14 0.0001 31.78 - 61.64  
0.45 0.13  
0.36 0.13  
0.012 0.06  
-0.91 0.24  
3.40 0.01  
2.74 0.006  
0.20 0.84  
-0.38 0.71  
0.19 – 0.71  
0.10 – 0.62  
-0.10 – 0.13  
-0.57 – 0.39  
percentiles to childhood BP measurement was queried .  
The current NIH BP standard that is in use is limited in  
that some of the data used were single BP readings, ob-  
tained by using cuff measurement based on the length of  
the arm (two thirds or three quarters) which are consid-  
ered incorrect by American Heart Academy and the  
Fig 1: The 5 , 10 , 50 ,  
th th  
0 and 95 percentiles  
of the male systolic  
blood pressure  
working group NHBPEP . This study thus provides nor-  
mative BP percentiles us1in3 g currently agreed methods  
by NHBPEP , the AHA and 1996 update of Task  
Force on Blood Pressure Control in Children for Nige-  
rian children age 5 to 15 years. In the absence of BP  
standards using currently agreed methods for BP deter-  
mination internationally and the non-representation of  
African children living in Africa, the normative BP per-  
centiles derived in this study would be suitable for use in  
Nigerian children. Although there is another Nigerian  
study that used at least 40% of cuff width; the study was  
on adolescents aged 10 to 18 years and BP percentiles  
Fig 2: The 5 , 10 , 50 ,  
th th  
0 and 95 percentiles  
of the female systolic  
blood pressure  
were not generated .  
The prevalence of hypertension in this study is similar to  
an earlier Nigerian study on adolescents aged 10 – 18  
years in Calabar 9b,2u0t lower than some other previous  
studies in Nigeria . The higher values obtained in the  
Fig 3: The 5 , 10 , 50 ,  
previous studies may reflect the differences in the envi-  
ronment stressors, weight and parameters affecting BP.  
The influence of environment on the casual BP of chil-  
th th  
0 and 95 percentiles  
of the male diastolic  
blood pressure  
dren was demonstrated in a study by Hamidu et al , in  
Kaduna State, Nigeria where the place of residence sig-  
nificantly influenced the BP of the children from three  
different communities . The prevalence of hypertension  
in this study and most other Nigerian studies is higher  
than the 1-2% quoted among Caucasian children . This  
suggests that the prevalence of childhood hypertension  
in Nigeria is higher than that reported amongst Cauca-  
sians. It is not clear why this is so. It may be related to  
differences in environmental stressors, or genetics.  
Fig 4: The 5 , 10 , 50 ,  
th th  
0 and 95 percentiles  
of the female diastolic  
blood pressure  
However, childhood essential hypertension is reported  
to be on the rise globally and besides the possibility of  
inheriting essential hypertension from their affected par-  
ents, another important associated factor is obesity and  
overweight whose prevalence is also on the rise  
Overweight/ obesity are caused by the sedentary life-  
style that includes television watching, video gaming  
and less physical exercise. This is further compounded  
by increased consumption of fast food . Studies have  
demonstrated similar lifestyle9among Nigerian children  
who are overweight and obese .  
females in this study. Perhaps because females are  
encouraged to stay at home and engage in indoor activi-  
ties like cooking while the males engage in more physi-  
cal activities ltihke playitnh g football and other outdoor  
games. The 90 and 95 percentiles for blood pressure  
in the males aged ten years and older was lower than  
those of the females, this is also due to the fact that the  
females were heavier than the males in this study.  
It is important to initiate programmes to stop this trend  
in Nigeria as this lifestyle among children portends a  
potential for higher prevalence of hypertension and other  
cardiovascular and metabolic abnormalities if the trend  
is not checked. Lessons can be learned from the United  
States experience in which a study done in 1994 by Arar  
et al , found that 23% of the hypertensive children had  
essential hyp6 ertension. By 2001 in another study by  
Flynn et al the proportion of children with essential  
hypertension was 48.6%. This rising trend of the burden  
of childhood essential hypertension is being attributed to  
the rising prevalence of overweight and obesity  
In conclusion, BP percentiles were derived for Nigerian  
children using cuff sizes based on the arm circumference  
in this study. The older females tend to have higher BP  
values compared to the males, a reversal of previous  
trend involving younger age group. These percentiles  
will be appropriate for use in Nigerian children pending  
the development of a National BP standard for children  
derived using recently agreed cuff specification and  
from the different zones of the country and pending  
when the BP values of African children resident in Af-  
rica are included in a new global BP standard like that of  
the NIH. Furthermore, there is a need to initiate a pro-  
gramme to address weight reduction in school children,  
especially the older girls who are heavier than their male  
The MSBP and MDBP of the male pupils were lower  
than that for the females for most ages; this is at vari-  
ance with previous studies that showed a higher BP for  
the male compared to the females until adolescence  
when the females now had higher BP . The lower male  
BP in our study may be due to the similarly higher mean  
weight for the female than the males for most ages,  
showing the pivotal role that weight plays in the predic-  
tion of BP as also has been demonstrated by previous  
studies . The height did not show similar strength of  
association also indicating the less important role height  
plays in prediction of BP . This fact is further but-  
tressed by the finding of weight and age as the only in-  
dependent predictors of BP in this study.  
Conflict of interest: None  
Funding: None  
It is not clear why the older males were lighter than the  
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