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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 3, May/June 2020
144
AFRICA
The mean (SD) SBP and DBP was 118 (13.2) and 71.8 (9.5)
mmHg, respectively, and BP was significantly higher among
students in the rural school than those in the urban school (Table
1). Overall, the prevalence of hypertension and pre-hypertension
was 13.1 and 15.5%, respectively (Table 2). There were no
urban–rural differences in hypertension and pre-hypertension.
Hypertension was more prevalent among male (OR = 4.3) than
female participants (Table 3).
Discussion
In this study, conducted among adolescents in a rural and urban
setting in Botswana, a high burden of hypertension was found
in constellation with obesity, tobacco use, alcohol use, obesity
and physical inactivity. All these may track from childhood
to adulthood and are predictive of increased cardiovascular
morbidity and mortality later in adult life.
10
For a country with
a high burden of HIV/AIDS, the increase in non-communicable
diseases is a challenge to the already stretched health system.
17,18
The prevalence of all the above risk factors has been increasing
among children, mainly as a consequence of urbanisation and
change in lifestyle,
11-13
with urbanisation leading to an increase
in the use of tobacco and alcohol, poor diet and physical
inactivity.
14-16
The prevalence of hypertension found in this study
was within the prevalence of 0.2 to 24.8% reported in the recent
meta-analysis of hypertension studies among African children
and adolescents.
30
Although our findings are consistent with previous studies,
we recognise that comparing the prevalence of paediatric
hypertension is a challenge due to differences in the definition
of hypertension, the age groups of the studied populations
and the blood measurement methodology. Nonetheless, the
burden of hypertension among our participants was appreciably
higher than the prevalence of 3 to 5% among adolescents in
the developed world.
31
We also observed a high prevalence of
pre-hypertension in our adolescents.
This is a cause for concern in Botswana where about a third of
adults are hypertensive.
32,33
As childhood hypertension progresses
Table 1. Characteristics of student participants at St Joseph’s and
Shakawe senior secondary schools (
n
= 252)
Characteristics
All
(
n
= 252)
St Joseph’s
(
n
= 120)
Shakawe
(
n
= 132)
p-
value
Mean age (SD), years
17.4 ± 0.9 16.74 ± 0.74 17.49 ± 0.9 < 0.001
Age groups, years
< 18 years,
n
(%)
182 (72.2)
104 (86.7)
78 (59.1)
< 0.001
≥ 18 years,
n
(%)
70 (27.8)
16 (13.3)
54 (40.9)
Gender
Girls,
n
(%)
172 ( 68.3)
83 (69.2)
89 (67.4)
0.767
Boys,
n
(%)
80 (31.7)
37 (30.8)
43 (32.6)
Height, mean (SD), cm
164.9 ± 8 163.42 ± 7.8 166.19 ± 8
0.006
Mean WC (SD), cm
69.3 ± 7.1 68.00 ± 7.8 70.49 ± 6.3
0.006
Mean weight (SD) kg
55.6 ± 9.9 55.3 ± 11.4 55.88 ± 8.7
0.670
Mean HC (SD), cm
91.3 ± 9.5 90.45 ± 11.2 92.0 ±7.5
0.208
Mean FBG (SD), mmol/l
4.70 ± 0.5 4.70 ± 0.44 4.71 ± 0.47
0.788
Mean SBP (SD), mmHg
118 ± 13.2 112.39 ± 12.6 122.62 ± 12.7 < 0.001
Mean DBP (SD ), mmHg
71.8 ± 9.5 68.5 ± 9.5
74.8 ± 8.4 < 0.001
Mean pulse (SD), bpm
80.3 ± 13.3 79.1 ± 11.7 81.4 ± 14.6
0.164
Family history of HPT,
n
(%)
75 (29.8)
42 (35)
33 (25)
0.083
Family history of DM,
n
(%)
15 (6)
10 (8.3)
5 (3.8)
0.128
Family history of stroke,
n
(%)
16 (6.3)
2 (1.7)
16 (10.6)
0.004
HPT: hypertension; DM: diabetes mellitus; FBG: fasting blood glucose; WC: waist
circumference; HC: hip circumference; BMI: body mass index; SBP; systolic blood pres-
sure; DBP: diastolic blood pressure; bpm: beats per minute, SD: standard deviation.
Table 2.Table showing the distribution of cardiovascular risk factors among
students at St Joseph’s and Shakawe senior secondary schools (
n
= 252)
Parameters
School
Gender
All
(
n
= 252)
St Joseph’s
(
n
= 120)
Shakawe
(
n
= 132)
p
-value
Female
(
n
= 172)
Male
(
n
= 80)
p
-value
Hypertension,
n
(%)
Normal
180 (71.4) 89 (74.2) 91 (68.9) 0.380 138 (80.2) 42 (52.5) < 0.001
PreHPT 39 (15.5) 19 (15.8) 20 (15.2)
20 (11.6) 19 (23.8)
Hyperten-
sion
33 (13.1)
12 (10)
21 (15.9)
14 (8.1) 19 ( 23.8)
Overweight or obesity,
n
(%)
Underweight 25 (9.9)
11 (9.2) 14 (10.6) 0.536 9 (5.2)
16 (20) < 0.001
Normal
weight
201 (79.8) 94 (78.3) 107 (81.1)
141 ( 82)
60 (75)
Overweight/
obese
26 (10.3) 15 (12.5) 11 (8.3)
22 (12.8)
4 (5.0)
WC, cm
Normal
229 (90.9) 108 (90) 121 (91.7) 0.109 162 (94.2) 77 (96.3)
0.491
Increased 23 (9.1)
12 (10)
11 (8.3)
10 (5.8)
3 (3.8)
Fasting blood glucose, mmol/l
Normal
248 (98.4) 118 (98.3) 130 (98.5) 0.923 168 (97.7) 80 (100)
0.169
IFG
4 (1.6)
2 (1.7)
2 (1.5)
4 (2.3)
0 (0.00)
Level of physical activity,
n
(%)
Inactive
95 (37.7) 32 (26.7) 63 (47.7) 0.002 70 (40.7) 25 (31.3)
0.164
Minimal
76 (30.2) 45 (37.5) 31 (23.5)
53 (30.8) 23 (28.8)
Highly active 81 (32.1) 43 (35.8) 38 (28.8)
49 (28.5)
32 (40)
Smoking,
n
(%) 5 (2)
3 (2.5)
2 (1.5)
0.567 1 (0.6)
4 (5.0)
0.019
Alcohol intake,
n
(%)
23 (9.1) 17 (14.2)
6 (4.5)
0.008 14 (8.1)
9 (11.3)
0.425
PreHPT: pre-hypertension; HPT: hypertension; BMI: body mass index; WC: waist circum-
ference; IFG: impaired fasting glucose.
Table 3. Factors associated with hypertension among students at
Shakawe and St Joseph’s senior secondary schools (
n
= 252)
Variable
Bivariate analysis
Multivariate analysis
Crude
OR 95% CI
p-
value Adjusted 95% CI
p
-value
Gender
Female
1 (ref)
1 (ref)
1 (ref)
1 (ref)
1 (ref)
Male
3.5 1.66–7.44 0.001* 4.31 1.83–10.13 < 0.001
School
Shakawe (rural)
1
St Joseph’s (urban) 0.59 0.28–1.25 0.168* 0.62 0.26–1.44
0.263
Age
0.98 0.66–1.46 0.923
Alcohol intake
No
1 (ref)
1 (ref)
Yes
3.57 0.47–27.44 0.221 4.86 0.44–54.0
0.198
Smoking
No
1 (ref)
1 (ref)
Yes
4.65 0.75–28.91 0.1 7.47 0.544–102.59 0.132
BMI category
Normal weight
1 (ref)
1 (ref)
Underweight
0.64 1.03–7.13 0.563 0.457 0.089–2.345 0.348
Overweight/ obese 2.72 1.03–7.13 0.043* 2.998 0.716–12.56 0.133
WC
1.07 1.02–1.13 0.005
Fasting blood glucose 1.32 0.59–2.93 0.496
Physical activity
Inactive
1.19 0.51–2.77 0.681
–
–
–
Minimally active
0.65 0.24–1.76 0.393
–
–
–
Highly active
1 (ref)
1 (ref)
–
–
–
Family history of
hypertension
0.73 0.31–1.69 0.458
–
–
–
Family history of
diabetes
1.022 0.22–4.75 0.980
–
–
–
Family history of
stroke
0.425 005–3.33 0.415
–
–
–
OR: odds ratio; CI: confidence interval; WC: waist circumference; BMI: body mass index.