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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 5, September/October 2016
318
AFRICA
weight group and the other three groups, and between the
overweight and the obese groups only.
Prevalence of cardiovascular risk factors according to BMI
classification is shown in Table 3. No relationship between fat
accumulation and the presence of risk factors was observed in
this age group. Moreover, prevalence of risk factors was similar
in both genders (Table 4).
Normal blood pressure values were found in 166 (83.8%)
children and elevated values were found in 29 (14.6%) children.
Simultaneous elevation of both SBP and DBP was found in
five children, while 16 showed an increase of only SBP and
eight showed an increase of only of DBP. Hypertension was
detected in nine children and pre-hypertension in 20, without
significant difference between genders (prevalence of 3.5 and
11.1%, respectively). Positive familial history of hypertension
was identified in 132 (66.7%) children. However, this trait was
not associated with the presence of elevated blood pressure in the
studied population (
χ
2
=
0.247,
p
=
0.618).
Another cardiovascular risk factor investigated was
dyslipidaemia. The frequency of this condition was quite high,
with 69.2% of the sample having at least one lipid value out of
the normal range for this age group. This finding was unrelated
to gender (71.4% for boys vs 67.8% for girls,
p
=
0.70) and BMI.
The most common change in lipid profile was the presence of
high total cholesterol levels, followed by an increase in LDL
cholesterol and triglyceride levels. Low HDL cholesterol level
was found in 9.1% of children, without a significant difference
between genders.
Table 5 shows the correlations between the three indices of
excessive fat accumulation and birth weight and cardiovascular
risk factors. Either SBP or DBP were moderately associated with
fat accumulation. This association was significant independent of
global (BMI and % fat) or central (WC) obesity indices. However,
no significant association was observed in our study between birth
weight and blood pressure or other cardiovascular risk factors.
An inverse correlation between fat accumulation and
HDL cholesterol level and glycaemia was also observed. In a
multivariate linear regression, we observed that body weight (kg)
was the only independent predictor of SBP (SBP
=
0.402
×
body
weight
+
90.8) while the fat mass (kg) was the only independent
predictor of DBP (DBP
=
0.759
×
fat mass
+
58.1).
Table 2. Physical and clinical characteristics of pre-pubertal
schoolchildren according to body mass index classification
BMI class
Underweight
(
n
=
11)
Normal
(
n
=
152)
Overweight
(
n
=
14)
Obese
(
n
=
21)
p-
value
Age (years)
9.6 ± 1.1 9.2 ± 1.0 9.6 ± 1.3 9.4 ± 1.4 0.707
Birth weight (kg)
3.27 ± 0.6 3.12 ± 0.6 3.46 ± 0.4 3.47 ± 0.4
#
0.046
Current weight (kg) 25.6 ± 6.6 30.1 ± 5.1 42.3 ± 8.8
#
52.1 ± 11.1
#§
<
0.001
Height (cm)
137.2 ± 15.4 136.4 ± 8.3 141.8 ± 10.8 141.7 ± 7.7
#
0.054
BMI (kg/m
2
)
13.3 ± 0.8
#
16.2 ± 1.4 20.8 ± 1.4
#
26.2 ± 3.6
#§
<
0.001
WC (cm)
50.6 ± 4.7
#
55.9 ± 4.7 68.1 ± 5.8
#
78.5 ± 1.7
#§
<
0.001
HC (cm)
62.4 ± 6.4
#
68.8 ± 6.1 83.7 ± 6.1
#
91.3 ± 7.8
#§
<
0.001
WHR
0.81 ± 0.04 0.81 ± 0.04 0.81 ± 0.03 0.86 ± 0.03
#§
<
0.001
Fat mass (kg)
3.6 ± 0.7 5.3 ± 1.8 10.5 ± 3.8
#
15.3 ± 4.6
#§
<
0.001
SBP (mmHg)
99.0 ± 8.9 103.1 ± 7.6 106.1 ± 6.7 113.1 ± 8.9
#§
<
0.001
DBP (mmHg)
60.7 ± 3.3 62.2 ± 6.4 65.3 ± 7.2 70.1 ± 7.5
#
<
0.001
HR (bpm)
85.5 ± 10.3 83.2 ± 10 81.4 ± 12.5 80.2 ± 9.7 0.585
Glycaemia (mg/dl)
(mmol/l)
91.3 ± 13.4
5.07 ± 0.74
87.5 ± 14.5
4.86 ± 0.80
83.7 ± 17.8
4.65 ± 0.99
82.0 ± 14.8
4.55 ± 0.82
0.327
TC (mg/dl)
(mmol/l)
194.6 ± 40.9
5.04 ± 1.06
170.6 ± 34.5
4.42 ± 0.89
176.3 ± 35.3
4.57 ± 0.91
166.3 ± 35.5
4.31 ± 0.92
0.127
Triglycerides (mg/dl)
(mmol/l)
75.8 ± 26.7
0.86 ± 0.30
63.4 ± 30.1
0.72 ± 0.34
49.7 ± 17.9
0.56 ± 0.20
77.5 ± 35.7
§
0.88 ± 0.40
0.039
LDL-C (mg/dl)
(mmol/l)
115.6 ± 40.3
2.99 ± 1.04
105.5 ± 32.4
2.73 ± 0.84
109.4 ± 32.3
2.83 ± 0.84
97.5 ± 34.6
2.53 ± 0.90
0.458
HDL-C (mg/dl)
(mmol/l)
63.5 ± 9.89
1.64 ± 0.26
58.7 ± 13.1
1.52 ± 0.34
56.5 ± 8.67
1.46 ± 0.22
54.9 ± 12.5
1.42 ± 0.32
0.256
LDL-C/HDL-C 1.83 ± 0.7 1.82 ± 0.7 1.97 ± 0.6 1.89 ± 0.91 0.973
Data presented as mean ± standard deviation, BMI; body mass index, WC, waist
circumference; HC, hip circumference; WHR, waist/hip ratio, SBP; systolic blood
pressure; DBP; diastolic blood pressure, HR; heart rate, TC, total cholesterol;
LDL-C; low-density lipoprotein cholesterol, HDL-C; high-density lipoprotein
cholesterol.
#
Difference between normal BMI with underweight, overweight and obesity;
§
Difference between overweight and obesity.
Table 3. Prevalence of cardiovascular risk factors in
pre-pubertal schoolchildren according to presence of
overweight or obesity (high weight group)
Variable
Body weight
p
-value
Normal
High
n
%
n
%
Prehypertension
13 7.97 7 20 0.066
Hypertension
6 3.7 3 8.6 0.416
Glucose intolerance
28 17.2 5 14.3 0.868
High TC (
≥
170 mg/dl) (
≥
4.4 mmol/l)
82 50.3 17 48.6 0.998
High LDL-C (
≥
110 mg/dl) (
≥
2.85 mmol/l)
67 41.1 15 42.8 0.998
Low HDL-C (
<
45 mg/dl) (
<
1.17 mmol/l)
16 9.8 3 8.6 0.929
High triglycerides
44 26.9 10 28.6 0.985
FHH
111 68.1 21 60 0.469
TC: total cholesterol, LDL-C: low-density lipoprotein cholesterol, HDL-C: high-
density lipoprotein cholesterol, FHH: family history of hypertension.
Table 5. Correlation coefficient between age,
anthropometric variable and birth weight in cardiovascular
risk factors in pre-pubertal schoolchildren
Variable
BMI
% fat
WC
Age
r
p
r
p
r
p
r
p
Glycaemia –0.146 0.02 –0.130 0.034 –0.095 0.092 0.000 0.50
TC
–0.099 0.083 –0.006 0.136 –0.095 0.091 0.017 0.41
Triglycerides 0.086 0.115 0.081 0.129 0.143 0.022 0.111 0.60
HDL-C –0.16 0.014 –0.109 0.064 –0.142 0.023 –0.02 0.40
SBP
0.460
<
0.05 0.370
<
0.05 0.462
<
0.05 0.20 0.02
DBP
0.401
<
0.05 0.432
<
0.05 0.416
<
0.05 0.128 0.03
Birth weight 0.169 0.009 0.208 0.002 0.193 0.003 –0.015 0.42
r
: Pearson correlation coefficient; BMI: body mass index; SBP: systolic blood
pressure; DBP: diastolic blood pressure; TC, total cholesterol; HDL-C: high-
density lipoprotein cholesterol; WC: waist circumference.
Table 4. Prevalence of cardiovascular risk factors by gender
CV risk factors
Boys
Girls
p-
value
n
%
n
%
Overweight
5 6.5 9 7.4 0.975
Obese
9 11.7 12 9.9 0.875
Prehypertension
8 10.4 12 9.9 0.893
Hypertension
4 5.2 5 4.1 0.996
Glucose intolerance
15 19.5 18 14.9 0.514
High TC (
≥
170 mg/dl) (
≥
4.4 mmol/l)
34 44.1 65 53.7 0.243
High LDL-C (
≥
110 mg/dl) (
≥
2.85 mmol/l)
32 41.5 49 40.5 0.998
Low HDL-C (
<
45 mg/dl) (
<
1.17 mmol/l)
14 18.2 5 4.1 0.002
High triglycerides
22 28.6 32 26.4 0.870
FHH
56 72.7 77 63.6 0.241
CV: cardiovascular, TC: total cholesterol, LDL-C; low-density lipoprotein
cholesterol, HDL-C: high-density lipoprotein cholesterol, FHH: family history
of hypertension.