Cardiovascular Journal of Africa: Vol 27 No 5 (September/October 2016)

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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 5, September/October 2016 320 AFRICA
available at the regional or national level in Angola, but a study
conducted in adults observed that 50.1% showed low HDL
cholesterol levels, while 11.1% showed hypercholesterolaemia,
and 10.6% hypertriglyceridaemia.35
The cut-off point adopted in our study, however, was used
to classify children from different genetic backgrounds and with
different dietary patterns. The prevalence of dyslipidaemias
found in our study [50% with total cholesterol levels > 170 mg/dl
(4.4 mmol/l)] is higher than the values found in some studies38-41
that used the same cut-off points. Other studies (Muscatine
study and Bogalusa Heart study) showed similar values to ours,42
however, the cut-off points were different from those used in our
study, making comparisons impractical.42
Regardless of cut-off points, it is important to highlight the
high prevalence of dyslipidaemia in children and adolescents.
For some authors, the change is due to the development of
insulin resistance, initially peripheral and later at the systemic
level.43 In our study, 16.8% of the children with dyslipidaemia
also showed impaired glucose tolerance. From the fasting
glycaemia determinations, we did not find diabetic children
in our sample. However, an inverse relationship was observed
between BMI and fasting glycaemia. This finding may be due
to the hyperinsulinaemic state of children with a higher body fat
accumulation.
Our study suggests that, similar to other countries in
sub-Saharan Africa, the high prevalence of overweight and
obesity and of other cardiovascular risk factor indicates a rapid
epidemiological transition affecting not only adults but also
children.44 Weight gain and dyslipidaemia may be associated with
environmental factors related to lifestyle, including inappropriate
eating habits and physical inactivity.
The consequences of childhood dyslipidaemia on the
cardiovascular health of adults was reported by Berenson et
al.45 who described a positive association between the extent of
arterial intima surface covered with atherosclerotic lesions and
elevated cholesterol and triglyceride levels as well as low HDL
cholesterol levels. According to Freedman et al.,46 dyslipidaemia
and overweight/obesity in childhood causes accumulation of
harmful effects over time, resulting in a thickened intima–media
layer of large arteries, atherosclerosis, arterial stiffness and
consequent increase in blood pressure, coronary artery disease
and stroke.
Limitations
Our study has some limitations. Children from a single school
were included, therefore our data cannot be translated to the
overall population of Luanda. Since the school is located in
a neighbourhood with families belonging to the middle class,
it represents only the population attending public school with
such characteristics. Moreover, the final sample (n = 198) was
sufficient to determine a prevalence around 10% only, with an
estimated error of 3.5% and power of 90%, making our study
inadequate for subgroup analysis.
We only included pre-pubertal children in the analysis to
avoid the influence of adolescence in fat accumulation. In this
group, the association between body fat and blood pressure can
be observed without the well-known influence of sex hormones.
Therefore, most of the analysis was conducted in the overall
sample, increasing the robustness of the conclusions.
Blood pressure was measured on a single day, which is
insufficient to establish a diagnosis of hypertension and rather
requires confirmation by additional measures. Our analysis,
however, was conducted by considering blood pressure as a
continuous variable.
Finally, cut-off points used in this study were based
on international references not validated for the Angolan
population. However, by using such international standards,
comparison with other studies was possible.
Conclusions
Our study shows a relatively high prevalence of obesity in
pre-pubertal schoolchildren in Angola and suggests a possible
association between fat accumulation and high blood pressure
in this age group. However, a causal relationship cannot be
established in this study given its transverse design. The high
prevalence of dyslipidaemia in the studied population deserves
attention in future studies, which should aim to investigate
potential causal relationships, including eating habits and genetic
factors. Early monitoring of blood pressure and lipid profile is
necessary for adoption of adequate prevention policies in the
area of cardiovascular health.
We acknowledge the collaboration of directors, teachers, students, parents
and guardians of the school Our Lady of Light (No 1170), the Graduate
Program in Physiological Sciences UFES. Financial support was received
from the Director of the Faculty of Medicine of the University of Agostinho
Neto, Angola and CAPES (the Brazilian Federal Agency for the Support and
Evaluation of Higher Education).
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