CARDIOVASCULAR JOURNAL OF AFRICA • Vol 21, No 4, July/August 2010
AFRICA
207
explained to each participant and they were given an opportunity
to ask questions. Thereafter informed consent was obtained.
Urbanised blackAfrican individuals (101 men and 99 women)
between 25 and 60 years of age who complied with the inclusion
criteria of having the same socio-economic status (SES) and
work environment were included. The exclusion criteria were:
pregnancy, lactation, high temperature (
>
37°C), users of
α
- and
β
-blocking agents, users of psychotropic agents, blood donors or
having been vaccinated in the past three months before taking
part in the study.
The participants were stratified into two groups: hypertensive
(HT) and normotensive (NT) men and women. This stratification
was done according to the European Society of Hypertension
(ESH) 2007 guidelines where average 24-hour ambulatory
hypertensive status is defined as systolic and/or diastolic blood
pressure (
≥
125–130/
≥
80 mmHg).
20
The study was approved by the Ethics Committee of the
North-West University, Potchefstroom Campus, in accordance
with ethical guidelines of the World Medical Association’s
Declaration of Helsinki.
21
Experimental procedure
The experimental procedure for each participant followed a two-
day protocol. On the first day, the Cardiotens device (Meditech
CE0120
®
) was applied and programmed to record the 24-hour
BP of four participants, one each day of the working week. The
physical activity meter was fitted around the waist and a physi-
cal activity (GPAIQ) questionnaire was completed at school.
Thereafter, the four participants left to resume their normal daily
activities. The Cardiotens device recorded BP measurements in
30-minute intervals during the daytime and in 60-minute inter-
vals during the night.
At approximately 16:40 the participants were transported to
the Metabolic Unit research facility of the North-West University
(research unit for human studies) where they stayed overnight.
The unit is well equipped with 10 furnished bedrooms, a kitchen,
two bathrooms and a dining area. The procedures for the evening
included a brief introduction to the apparatus to minimise the
‘white-coat effect’,
22
and a tour of the facilities. Completion
of the psychosocial battery of questionnaires followed, under
supervision of registered psychologists and fieldworkers. The
questionnaires were arranged in such a way as to reduce the
effects of participant fatigue, with half the questionnaires being
completed before dinner, and the remaining half thereafter. The
participants had dinner at 18:00 and enjoyed their last beverages
between 20:00 and 22:00 (tea/coffee and biscuits) before going
to bed at 22:00.
The procedure for day two included the disconnection of the
Cardiotens apparatus at 06:00. After obtaining the anthropo-
metric measurements, the participants were taken to the blood
pressure station where the cardiovascular measurements were
obtained while the participants were in a semi-Fowlers position.
The same procedures were followed for the rest of the partici-
pants daily.
Demographic questionnaire
Included in the demographic questionnaire were questions on
smoking and alcohol consumption. These are self-report ques-
tions with a ‘yes’ or ‘no’ answer. Information on physical activity
levels was obtained with the Global Physical Activity question-
naire.
23
This measures the total physical activity participation in
three domains: (1) activity at work, (2) travel to and from places
and (3) recreational activities. The sum of these domains were
then evaluated and summed in calories per week. Physical activ-
ity is classified as high (vigorous-intensity activity on at least
three days, achieving a minimum of 1 500 METS-minutes/week,
or seven or more days of any activity accruing at least 3 000
METS-minutes/week) or low (not meeting any of the above
criteria).
23
Psychological questionnaires
The 28-item GHQ
13
is used for the assessment of signs and
symptoms of psychological dysfunction and is useful for under-
standing various sources of distress in occupational research.
24
The GHQ is a measure of common mental health and focuses on
symptom domains for depression, anxiety, somatic complaints
and social withdrawal.
23
The GHQ was validated for use within the Setswana-speaking
population prior to the study.
25
An example of items used in this
questionnaire include: ‘Have you found everything getting on
top of you?’, ‘Have you been getting scared or panicking for no
reason?’ and ‘Have you been getting edgy and bad tempered?’.
Each of the above are then accompanied by four possible
responses; ‘not at all’, ‘no more than usual’, ‘rather more than
usual’ and ‘much more than usual’. In this study each item was
evaluated using the binary scoring method.
26
The two least symptomatic answers are given a score of nil (0)
while the two most symptomatic answers are given a value of one
(1). Total scores exceeding the threshold of four are classified as
achieving ‘psychiatric caseness’. In general practice, individuals
classified as achieving ‘psychiatric caseness’ would be likely
to receive further attention.
25
The reliability coefficients of the
subscales for this questionnaire varied between 0.77 and 0.83.
The Patient Health questionnaire (PHQ) is a sensitive nine-
item instrument for making criteria-based diagnosis of depres-
sive disorders and it is also a reliable and valid measure of
severity of depression.
14
The scale is based on the actual nine
criteria of diagnosis of the DSM-IV depressive disorders. The
PHQ assesses diagnoses divided into threshold disorders (disor-
ders that correspond to specific DSM-IV diagnoses, i.e. major
depressive disorder) and sub-threshold disorders (disorders
whose criteria include fewer symptoms than required for any
specific DSM-IV diagnoses, i.e. other depressive disorders). The
questionnaire scores each of the nine DSM-IV diagnostic criteria
as being experienced ‘0’ (not at all) to ‘3’ (nearly every day).
For analysis, the PHQ-9 scores are divided into the following
categories of increasing severity: 0–4, 5–9, 10–14, 15–19 and
20 or greater, which represent minimal, mild, moderate, moder-
ately severe, and severe depression, respectively. Scores less than
five signify the absence of depressive disorders, scores of 5–9
predominantly represent no depression or sub-threshold depres-
sion, scores of 10–14 represent a spectrum of individuals who
may or may not display depression, and scores of 15 or higher
usually are indicative of major depression.
14
In this study, scores
of
≤
10 were considered as the absence of depression (MDD
=
0) and values
>
10 were considered as the presence of major
depression (MDD
=
1).
14
The Cronbach alpha-reliability index
for this sample was 0.81.
