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 316 AFRICA
primary education in a public school in Luanda, the Angolan
capital. The project was carried out after obtaining authorisation
from the Provincial Directorate of Education, the Education
Chamber of Rangel municipality and the directors of the school
5008 (Our Lady of Light).
Consent for the involvement of the community in the study
was obtained in meetings with the school staff, parents and/
or guardians of the children and the children to clarify the
study purposes and methods. The project was approved by the
Independent Ethics Committee on Research of the Faculty
of Medicine of Agostinho Neto University, following the
standards procedures in human research in accordance with the
Declaration of Helsinki.
In the 2011 academic year, 1 015 students (aged five to 12
years) were enrolled in the Our Lady of Light school and 719
(70.8%) were eligible for the study (seven to 11 years). This school
was chosen because it is near the Faculty of Medicine, where
data were collected and because it is located in a neighborhood
with most of the families belonging to the middle class.
After meeting with parents or guardians, we sent an
envelope containing an invitation letter and a questionnaire
to a random subsample of 290 students. The questionnaire
required completion for information on the conditions of birth
and the child’s life, including pregnancy history, birth weight,
period of exclusive breastfeeding, self-reported diseases, and
sociodemographic information of the family. Information about
birth weight and the duration of exclusive breastfeeding in
addition to signing of the consent form were necessary for final
inclusion in the project.
Of the 290 questionnaires distributed, 248 (85.5%) were
returned. Eleven children were excluded due to lack of essential
information. Of the 237 selected, 23 did not appear at the venue
for the examination. The set of examinations to investigate the
presence of cardiovascular risk factors was performed on 214
children.
All children were classified according to the Tanner scale, 20
obtained by self-evaluation of genitalia and breast development.
According to this procedure, 16 children were excluded from our
analysis because they were in Tanner stage II, or because they
had completed 12 years between enrolment and the examination.
Therefore, the data in this study refer to 198 pre-pubertal
(Tanner stage I) and apparently healthy schoolchildren.
All study participants presented to the Laboratory of
Functional Tests and Physiology of the Faculty of Medicine on
a pre-scheduled morning in a fasting condition (10–14 hours).
Examinations were performed from June 2012 to November
2013. A previous pilot study (March 2012) was performed
on 30 children (not included in this study) to standardise the
protocol and to train examiners. Sociodemographic data (age,
gender, race, school grade), physical activity and dietary habits
were obtained in an interview with the child and the mother or
guardian.
Blood was collected by venipuncture of the forearm and
processed on the same day by the Department of Biochemistry
(Faculty of Medicine) to determine glucose, urea, uric acid,
creatinine, total cholesterol, high-density lipoprotein (HDL)
cholesterol and triglyceride levels. Only reagents of BioSystems
SA (Barcelona, Spain) were used. Low-density lipoprotein (LDL)
cholesterol concentration was calculated by the Friedewald
formula for triglycerides < 400 mg/dl (4.52 mmol/l).
Biochemical variables in the blood were classified according to
the criteria established by the American Academy of Pediatrics
and the American Heart Association (American Guidelines for
Cardiovascular Health and Risk Reduction in Children and
Adolescents 2012).21 In brief, the lipid profile was classified as
follows:
• total cholesterol < 170 mg/d (< 4.4 mmol/l): acceptable;
170–199 mg/dl (5.15 mmol/l): borderline; ≥ 200 mg/dl (≥ 5.18
mmol/l): high
• LDL cholesterol < 110 mg/dl (< 2.85 mmol/l): acceptable;
110–129 mg/dl (2.85–3.34 mmol/l): borderline; and ≥ 130 mg/
dl (≥ 3.37 mmol/l): high
• triglycerides (0–9 years) < 75 mg/dl (< 0.85 mmol/l): accept-
able; 75–99 mg/dl (0.85–1.12 mmol/l): borderline; ≥ 100 mg/dl
(≥ 1.13 mmol/l): high
• triglycerides (10–19 years) < 90 mg/dl (< 1.02 mmol/l): accept-
able; 90–129 mg/dl (1.02–1.46 mmol/l): borderline; and ≥ 130
mg/dl (≥ 1.47 mmol/l): high
• HDL cholesterol > 45 mg/dl (> 1.17 mmol/l): acceptable;
40–45 mg/dl (1.04–1.17 mmol/l): borderline; and < 40 mg/dl
(< 1.04 mmol/l): low.21
According to fasting blood glucose criteria, the children were
classified as normoglycaemic (60–99 mg/dl) (3.33–5.49 mmol/l),
glucose intolerant (100–125 mg/dl) (5.55–6.94 mmol/l) or
hyperglycaemic (> 125 mg/dl) (> 6.94 mmol/l). No child was on
treatment with insulin or oral hypoglycaemic agents.
Body weight was obtained using a digital electronic scale
(SECA, Mod 763, Germany) with 0.1-kg precision while
fasting and after voiding. Children were barefoot and clothed
with undergarments only. Height was measured using a fixed
stadiometer with 0.5-cm precision. The child was placed on the
central part of the scale platform with heels together, head and
buttocks resting against the stadiometer and eyes looking toward
the Frankfurt horizontal plane.
The body mass index (BMI) was calculated by dividing body
weight by height squared (kg/m2). Percentiles (P) of height, weight
and BMI of each child were calculated as presented in https://
2 BMI classification was obtained
according to the following World Health Organisation (WHO)
parameters: underweight (BMI < P5), normal (BMI ≥ P5 and <
P85), overweight (BMI ≥ P85 and < P95) and obese (BMI ≥ P95).23
The left arm circumference was obtained with an inelastic tape
at the midpoint between the acromion (proximal) and olecranon
process (distal). The waist (WC) and hip circumferences (HC)
were measured with an inelastic tape with the child in a standing
position and at the end-expiration phase. Measurements (0.1-
mm precision) were obtained in front of a mirror to facilitate the
tape positioning in the horizontal plane. WC was measured at the
midpoint between the lower edge of the rib cage and the anterior
superior iliac crest. HC was measured at the level of the great
trochanter, circling the hip on the most prominent point between
the waist and the thigh. The waist-to-hip ratio (WHR) was
obtained by dividing WC by HC. The thickness of four skinfolds
(triceps, supra-iliac, subscapular and abdominal) was measured
with a manual caliper (Sanny) with a precision of 1 mm.
Body composition was obtained by tetrapolar bio-impedance
with the Maltron BioScan Analyser (Model 916, Maltron Int
Ltd, UK). Two electrodes were placed on the dorsal surface of
the radiocarpal joint and metacarpal of the right hand and the
other two on the dorsal surface of the right foot (tibiotarsal