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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 29, No 6, November/December 2018
AFRICA
367
the stressor; emotional avoidance or passive coping, resulting
in withdrawal or loss of control to a stressor; and seeking
social support.
13-17
Findings have shown that DefS involves a
beta-adrenergic-mediated pattern of stimulation that causes
increases in systolic blood pressure (SBP) and cardiac output via
central cardiac mechanisms. Emotional avoidance is mediated by
alpha-adrenergic pathways, causing elevated DBP via vascular
mechanisms, with increases in vascular resistance and decreases
in stroke volume.
15,16
Ineffective ways of coping and a lack of social support among
black teachers from an urban environment were the major
factors that resulted in hypertension.
16-19
However, trajectories of
culture-specific coping styles may further expand our knowledge
on stress-related hypertension, and have not yet been investigated
in SSA. Hence, we took the current findings one step further
by examining prospective associations between hypertension,
depression, coping style and cultural coping in a South African
bi-ethnic gender cohort over a three-year period.
Methods
The Sympathetic Activity and Ambulatory Blood Pressure in
Africans (SABPA) prospective study was conducted in 2008/9
and 2011/12 (Fig. 1). This three-year follow-up investigation
was performed using a similar methodology to the baseline
evaluation, with clinical assessments done over a 48-hour
period. The recruitment, selection process, methods and ethical
considerations have been described extensively elsewhere.
18
Black Africans (blacks) and Caucasian Africans (whites)
included 409 school teachers (aged 20–65 years) from the Dr
Kenneth Kaunda Education District in the North-West Province,
South Africa (Fig. 1). Teachers were chosen as participants to
ensure homogeneity with regard to socio-economic status. They
all had tertiary education (diploma/degree) and were in the same
profession, with access to medical aids and benefits, such as
annual bonuses and pension funds. The teachers resided in the
Potchefstroom, Ikageng and Klerksdorp suburbs, with access to
electricity and running water.
Exclusion criteria included tympanum temperature above
37.5°C, use of psychotropic substances, and blood donors
or individuals vaccinated within three months before data
collection. For the current sub-study, only teachers participating
in both phases (
n
=
359) were included.
All participants provided their signed, informed consent.
The study was approved by the ethics committee of the North-
West University (NWU-00036-07-A6) and complied with the
Declaration of Helsinki criteria for human research.
Clinical measures were done over 48 hours on working days
of the week. On day one, between 07:00 and 08:00, teachers were
fitted with 24-hour ambulatory BP monitors and accelerometers.
The BP monitors were fitted onto each teacher’s non-dominant
arm and hip, using suitable cuff sizes (Cardiotens CE120
®
,
Meditech, Budapest, Hungary; Actical
®
, Montreal, Quebec).
Teachers proceeded with their normal daily teaching and
extra-curricular activities and were asked to record occurrences
of stress, physical activity, headache, syncope, dizziness, nausea,
palpitations, hot flushes and visual disturbances on their
ambulatory diary card. Blood pressure (BP) was automatically
measured by the Cardiotens CE120
®
devices at intervals of
30 minutes between 08:00 and 22:00 and at intervals of 60
minutes between 22:00 and 06:00 the following morning, with
a successful mean inflation rate of 84.9 and 91.8% for the black
and white groups at the second phase, respectively. Cohort
members were classified as hypertensive using the European
Society of Cardiology guidelines when they recorded an average
24-hour BP of
≥
130 mmHg SBP and/or
≥
80 mmHg DBP.
After school, at 16:30, participants were transported to
the North-West University’s Metabolic Unit research facility
for an overnight stay in a well-controlled setting where they
were familiarised with the study set-up. Registered clinical
psychologists supervised each member’s completion of a
psychosocial battery, followed by dinner for the participants
at 18:00. Teachers were asked to go to bed at 22:00 and to fast
overnight in preparation for the second day’s clinical measures.
On day two, they were woken at 07:00 for anthropometric
measurements and were in a semi-recumbent position for at least
30 minutes before a registered nurse took fasting blood samples
and trained staff performed a battery of clinical assessments.
Medical history and medication usage questionnaires were
completed. Immediately available results were communicated
to the participants where-after they received breakfast and were
transported back to school.
The Actical
®
omnidirectional accelerometer measured the
total energy expenditure of each participant for 24 hours. The
device was set to 15-second intervals to measure the movement
of the participants while they engaged in normal daily activities.
Gamma-glutamyl transferase (
γ
-GT) levels were measured as a
marker of alcohol abuse and cotinine levels reflected smoking
status.
20,21
All anthropometric measures were conducted in
triplicate by ISAK (International Society for the Advancement
Exclusion criteria: pregnancy, lactation, users of
α
- and
β
-blockers,
psychotropic substance abuse, blood donors/vaccinated in previous
3 months, tympanum temperature > 37.5°C
Black and white teachers, aged 20–65 years
Invited:
n
= 2 170
Screened:
n
= 471
Phase 1:
Non-respondents: 62
Responders: 409 eligible and enrolled
Whites (209)
101
♂
108
♀
Blacks (200)
101
♂
99
♀
Phase 2:
3-year follow up
(
n
= 359)
Whites
Deceased: 1
♂
, 1
♀
Pregnant: 1
♀
Losses: 7
♂
, 12
♀
Blacks
Deceased: 5
♂
, 2
♀
Lactating: 1
♀
Losses: 6
♂
, 14
♀
Fig. 1.
Designof thebi-ethnic gender cohort of theSympathetic
Activity and Ambulatory Blood Pressure in Africans
prospective study.