CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 7, August 2012
372
AFRICA
through a variety of mechanisms.
17
Diet can, therefore, be seen as a risk factor for CVD and
dietary recommendations create the cornerstone in prevention of
CVD.
17
To be effective and successful, any dietary intervention
programme should be focused, using dietary messages,
educational material and nutritional advice targeted at specific
groups.
18
It is therefore important for prevention of CVD to know
which groups within a population have a high risk for CVD and
which risk factors should be targeted with dietary interventions.
In this study of an African population undergoing a
nutritional transition in the North West Province of South
Africa, we explored the associations between SES (measured
by level of urbanisation, education and employment) and CVD
risk factors (including diet and nutrient intakes) that were
prevalent in 2005 when the baseline PURE data were collected.
PURE is an acronym for the 12-year Prospective Urban and
Rural Epidemiological study, which is investigating the health
transition in urban and rural Africans between 2005 and 2017.
The objective of this study was to assess whether social drift in
CVD risk has taken place over a period of nine years in Africans
of the North West Province, by comparing the findings of the
baseline PURE study data to those reported for the THUSA
study,
4
which was collected from 1996 to 1998.
Methods
This analysis is based on cross-sectional data collected at
baseline in 2005 as part of the North West Province, South Africa
leg of the international 12-year PURE study. The PURE study is
investigating the effects of the health and nutritional transitions,
and specifically of NCDs or chronic diseases of lifestyle in urban
and rural subjects.
Migration stability was the main selection criterion within
the chosen rural and urban communities. Four different areas
of residence were used in the subject recruitment for the PURE
study. Community A, a rural community, was located 450 km
west of Potchefstroom on the highway to Botswana. Community
B, a deep rural community 35 km east of A, was only
accessible via a gravel road. Communities C and D were urban
communities; C was the established Ikageng township, part of
the greater Potchefstroom, and D was the informal settlements
surrounding community C.
A random household census regarding number of people, their
ages and health profiles was done in 6 000 houses (1 500 in each
community). Every head of a household gave signed consent to
fill in the census questionnaire (see appendix on CVJA website
under journal archives). If a person refused or was not at home,
the next house was taken and a non-complier questionnaire was
filled in. From the data obtained, a paper selection of possible
subjects with no reported NCDs, tuberculosis or diagnosed HIV
was made.
A total of 2 010 apparently healthy African volunteers, 35
years and older, were then recruited. Participants were fasted
(10–12 hours) for the baseline blood sampling and other
measurements. Trained field workers assisted in providing
information to the participants in their language of choice.
Participants received feedback regarding their blood pressure,
fasting glucose concentrations and HIV status, and were referred
to the nearest clinic or hospital where necessary. Travelling
expenses of participants were covered.
Ethical approval was obtained from the Ethics Committee
of the North-West University, Potchefstroom, South Africa
(ethics number: 04M10) and signed informed consent forms
were received from all participants. Subjects were provided with
background information on the study and its purpose, and they
were informed that participation was voluntary and they could
withdraw at any time. Permission to conduct the study was
also obtained from the North West Department of Health, tribal
chiefs, and the local government authorities of each selected site.
Structured, validated demographic, socio-economic and
lifestyle questionnaires were administered by trained field
workers during home visits in the language preferred by
the participants. The questionnaires used were adapted from
those used by all countries participating in the PURE study. A
quantitative food frequency questionnaire (QFFQ), validated for
this population,
19
was administered by trained field workers using
food models and food photographs of different portion sizes to
assess habitual dietary intakes. The food data were converted to
nutrient intakes using the South African food composition tables
and computer program of the South African Medical Research
Council.
20
Anthropometric measurements were done by trained
biokineticists. Height was measured to the nearest 0.5 cm with a
stadiometer (Invicta, IP 1465, UK) and weight was determined
on a portable electronic scale to the nearest 0.01 kg (Precision
Health Scale,A&D company, Japan).All the measurements were
done according to the guidelines adopted at the National Institute
of Health-sponsored Arlie Conference.
21
Body circumferences of
participants were measured in light underwear with calibrated
instruments (Holtain – unstretchable metal tape; John Bull –
calipers). Body mass index was calculated by dividing weight in
kilograms by height in square metres.
Every participant who signed an informed consent form was
tested for HIV infection, but was given the choice of knowing
his/her status. Whole blood was used for the determination of
HIV status, making use of the First Response (PMC Medical,
India) rapid HIV card test. If tested positive, the test was repeated
with the Pareeshak (BHAT Bio-tech India) card test. Pre-test
counselling was done in groups of 10 persons before the blood
sample was taken, and post-test counselling was individualised,
according to the protocol of the National Department of Health
of South Africa.
A disposable needle was used to draw blood from the ante-
cubital vein in the right arm of the participants. For plasma,
each collection tube was filled to its capacity to ensure optimal
blood:anticoagulant ratios. The tubes were inverted five times to
ensure thorough mixing of the contents of the tube. The tubes
were placed in ice boxes after labelling.
A new sterile transfer pipette was used to aliquot blood cell,
serum and plasma samples for analysis. Serum was prepared by
allowing blood to clot at room temperature for 30 min; it was
then centrifuged at 2 000 ×
g
for 15 min at 10ºC. Blood was
centrifuged within two hours of collection, separated and stored
at –70ºC. Plasma samples were collected in ethylenediamine
tetra acetic acid (EDTA) tubes, centrifuged at 2 000 ×
g
for 15
min at 4ºC and transferred to cryo-tubes for storage at –70ºC.
Both systolic and diastolic blood pressures were obtained
using an OMRON automatic digital blood pressure monitor
(Omron HEM-757). Subjects did not smoke, eat, exercise or do
any intense activities for 30 min before taking the measurements,
and they were rested and calmed for 10 min before doing the
