CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 5, September/October 2011
262
AFRICA
Township (SOWETO) of Johannesburg, South Africa, using the
population census figures of 2001. From the time of initiation
of the study until the end of 2009, 1 029 participants have been
studied.
A standardised questionnaire
18-25
was administered to obtain
demographic and clinical data. In order to avoid translational
errors, the questionnaire was not translated into an African
language, but study assistants familiar with all languages spoken
in SOWETO and who either previously lived in or currently
reside in SOWETO assisted with the completion of each ques-
tionnaire. However the majority of participants were reasonably
proficient in English.
Only same-sex assistants were used to assist each family
member with the completion of the questionnaire. Assistance
was provided only when requested. Study assistants first visited
homes of subjects who agreed to participate in the study in order
to familiarise participants with the questionnaire. The ques-
tionnaire was completed at a subsequent clinic visit and then
ambiguities were checked by performing a follow-up home visit.
If family members were absent at follow-up home visits, data
were checked with them personally via telephonic conversations
whenever possible. Ambiguities in answers to the questionnaire
were detected by an independent observer prior to a second home
visit. A pilot study was conducted in 20 participants to ensure
that data obtained in the questionnaires were reproducible when
obtained with the assistance of two separate study assistants.
The questionnaire requested specific answers to date of birth,
gender, previous medical history (including the presence of
hypertension, diabetes mellitus and kidney disease), previous
cardiovascular events (including stroke, myocardial infarction or
heart failure), the presence of angina pectoris, prior and current
drug therapy (analgesic, antihypertensive use and glucose lower-
ing agents included), smoking status (including the number of
cigarettes smoked in the past and at the present time), daily
alcohol consumption (beer, traditional beer or other forms of
alcohol and the daily quantity), caffeine consumption (number of
cups of tea or coffee and whether they are decaffeinated, and the
number of colas a day), exercise frequency, and family history of
hypertension. For females, menstrual history, history of pregnan-
cies and use of oral contraceptives was evaluated. Most of the
questions simply required a ‘yes’/‘no’ answer, but understanding
was assessed by requesting some short answers. If participants
were unable to provide the name of medications taken, these
were obtained on a second home visit.
High-quality conventional BP measurements were obtained
by a study nurse using a standard mercury sphygmomanometer,
as previously described.
19
After being trained in the procedure,
including being shown the pitfalls of BP measurement (position-
ing of the cuff, positioning of the arm, first estimating systolic
BP using a radial pulse measure in order to avoid inflating cuff
pressures too high, detecting auscultatory gaps, releasing valve
pressure at the correct speed, using the correct cuff size, etc) the
observer demonstrated an ability to perform the procedure on 20
participants.
The study assistant was able to measure BP on a separate
group of 20 participants, including patients with hypertension,
to within 4 mmHg of an experienced investigator obtained with
a stethoscope with two ear pieces. The study assistant was also
able to detect phase I and V sounds under different circum-
stances, including in the presence of a wide auscultatory gap and
where phase V Korotkoff was taken as a ‘muffling’ rather than a
‘disappearance’ of sounds (Blood Pressure Measurement,
British
Medical Journal
, BMA House London).
A standard cuff with a 12
×
24-cm inflatable bladder was
used to assess conventional BP, but if upper arm circumference
exceeded 31 cm, larger cuffs with a 15
×
35-cm inflatable blad-
der were used. After 10 minutes of rest in the seated position,
five consecutive BP readings were taken 30 to 60 seconds apart
with the participants in a seated position, followed by a pulse
rate count. The cuff was deflated at approximately 2 mmHg per
second, and phase I (systolic) and phase V (diastolic) BP was
recorded to the nearest 2 mm Hg. The average of the five read-
ings was taken as the office BP.
In the present study, quality control of conventional BP
assessments was assessed as previously described.
26
Only 0.68%
of visits had fewer than the planned BP recordings. The frequen-
cy of identical consecutive recordings was 0.87% for systolic and
2.24% for diastolic BP. The occurrence of BP values recorded as
an odd number was 0%. Of the systolic and diastolic BP read-
ings, 30.1% ended on a zero (expected
=
20%).
Body height, weight, waist and hip circumference, and
triceps and subscapular skin-fold thickness (Harpenden Skinfold
Calliper, Bedfordshire, UK) were measured during the clinic
visit by a trained observer. Height and weight were measured
with the participants standing and wearing indoor clothes with
no shoes. Waist and hip circumferences were measured accord-
ing to conventional techniques. Body mass index (BMI) was
calculated as weight in kilograms divided by the square of height
in metres, and waist-to-hip ratio was calculated as an index of
central obesity. Participants were identified as being overweight
if their BMI was
≥
25 kg/m
2
and obese if it was
≥
30 kg/m
2
.
Participants were identified as having central obesity if waist
circumference exceeded 102 cm in men and 88 cm in women.
Blood samples were obtained on the day of the visit and the
South African National Health Systems Laboratories (NHSL)
contract laboratory services (established for scientific studies)
performed a full blood count and differential count, measured
urea, creatinine and electrolyte concentrations, assessed liver
function (from alanine transaminase, aspartate transaminase,
gamma glutamyl transpeptidase, alkaline phosphatase, albumin,
total protein and plasma albumin, total bilirubin, and conjugated
and unconjugated bilirubin concentrations), measured plasma
urate concentrations, determined a lipid profile (total cholesterol,
and low-density lipoprotein cholesterol, high-density lipoprotein
cholesterol and triglyceride concentrations), and performed a
blood glucose measurement and percentage glycated haemoglo-
bin (HbA
1c
). A ‘spot’ urine analysis was also performed to screen
for major clinical conditions, such as diabetes mellitus (DM) and
renal pathology.
Cardiovascular risk was defined using two approaches. Risk
was assessed according to the Southern African Hypertension
Society (SAHS) guidelines
27
which are similar to the recently
published European Society of Hypertension/European Society
of Cardiology (ESH/ESC) guidelines.
16
These guidelines suggest
that antihypertensive treatment should be instituted in people
with a high or very high added risk, which equates to an absolute
10-year risk of a cardiovascular event of 20–30% (high added
risk) or
>
30% (very high added risk).
16,27
Second, cardiovascular risk was defined according to
the World Health Organisation and International Society of
