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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 3, May/June 2021
AFRICA
157
and stroke. This requires the appropriate management of CVD
risk factors such as hypertension, diabetes and dyslipidaemia,
and optimal diagnosis and management of CHD and stroke by
adequately trained healthcare professionals.
We are not aware of any nationwide study in South Africa
that has assessed and pooled the available evidence on the
burden of CHD and stroke. Therefore, this systematic review and
meta-analysis aimed to estimate the pooled prevalence of CHD
and stroke in South Africa over a period from 1990 to 2017. The
findings of this systematic review and meta-analysis provide the
depth and quality of evidence, which will support and inform
policies and interventions regarding CHD and stroke in South
Africa.
Methods
The systematic review of rationale and methods was specified in
advance and documented in a protocol, which was published in
the PROSPERO register (CRD42017068585). Ethical approval
was not required for this study.
We included population-based surveys, modelling, prospective
or retrospective cohort studies, case–control studies, and cross-
sectional studies with crude or adjusted national prevalence
and incidence estimates of CHD or stroke. Our interest was in
participants with a diagnosis of CHD, namely acute myocardial
infarction (MI), previous MI (ST-segment elevation MI and
non-ST-segment elevation MI), unstable or stable angina, and
those with a confirmed diagnosis of ischaemic and haemorrhagic
stroke. Participants with a self-reported history of CHD or
stroke were also included.
A search of the following electronic bibliographic databases
was conducted: PubMed, Scopus, and Web of Science. An
additional searchwas carriedout onGoogle Scholar and reference
lists of relevant studies were used to identify publications that
could have been omitted in the database searches. The search
strategy was edited to find epidemiological studies that focused
on CHD and stroke. The search terms used are given in Table
1. The study setting was South Africa, and studies that had not
been conducted in South Africa were excluded. Only English
studies published between January 1990 and July 2017 were
eligible for inclusion in the review.
Three reviewers (NA, NP and SOMM) independently
evaluated the eligibility of the studies obtained from the literature
searches. All articles yielded by the database search were initially
screened by their titles and abstracts to obtain studies that met
our inclusion criteria. In cases of discrepancies, an agreement
was reached by discussion.
Data extraction was completed by one reviewer (NA) and
comprised study title, author(s), year of study and publication;
data source; population characteristics such as age, gender and
study setting; and risk of bias criteria. Prevalence and incidence
estimates were extracted for studies assessed to have a low or
moderate risk of bias.
One reviewer (NA) assessed the risk of bias (ROB) for each
study using a framework developed by Pillay-van Wyk
et al
.
16
The framework assesses the external and internal validity of each
relevant study and was developed for observational studies. The
overall quality score ranges from 1 to 20 (high risk of bias = 1 to
6; moderate risk = 7 to 13 and low risk = 14 to 20). This quality
assessment can be evaluated as a source of heterogeneity or in
the form of sensitivity analysis in which overall results can be
compared with those obtained from studies with defined subsets
of quality characteristics.
17
However, this was not done in this
study and was only used to assess low- and moderate-risk studies
to be included in the meta-analysis.
Statistical analysis
Themainparameters of interest were the prevalence and incidence
of CHD and stroke. Random-effects meta-analyses were used
to pool the prevalence estimates for the two cardiovascular
conditions, with 95% confidence intervals (CI) and
p
-values.
Incidence estimates were only found in one study (for both
CHD and stroke) and could not be pooled to provide an overall
estimate. The random-effects model incorporates heterogeneity
resulting from variation between studies and assigns greater
variability to the estimate of the overall effect.
18,19
Heterogeneity among study estimates was quantified using
Higgins
I
2
, which computes the proportion of variance between
studies due to heterogeneity rather than chance.
20
We considered
an
I
2
value greater than 50% as indicative of substantial
heterogeneity and conducted sensitivity analyses to assess the
robustness of the meta-analysis results in outlying effect sizes
and studies that looked at subgroups of people. To evaluate
possible causes of heterogeneity, subgroup analyses or stratified
analyses are recommended; however, if the total number of
studies is less than 10, it would not make sense to compare two
or more subgroups.
21
Stata 15
22
was used for all analyses.
Results
The PRISMA flow diagram displays the process of selecting
the studies
23
(Fig. 1). The literature search returned 2 959
publications (2 705 for CHD and 254 for stroke) from PubMed,
Scopus and Web of Science. After removing duplicates, 2 466
publications remained. After the screening of titles and abstracts,
2 343 publications were excluded, giving a total of 123 full-text
articles that were assessed. A total of 12 studies were retained for
the final review (five for CHD and seven for stroke).
The 12 studies retained provided population-level prevalence
and only one study provided incidence estimates of CHD and
Table 1. Search terms used to find CHD and stroke studies
Search Query
Coronary heart disease
#1
Search (‘Coronary disease’ OR ‘Myocardial infarction’ OR ‘Coro-
nary artery disease’ OR ‘Angina pectoris’ OR ‘Unstable angina’ OR
‘Cardiovascular disease’ OR ‘Coronary heart disease’ OR ‘Ischaemic
heart disease’ OR ‘Heart attack’ OR ‘Ischaemic heart disease’)
#2
Search (South Africa OR ‘South Africa*’ OR RSA OR Africa, South-
ern OR ‘Southern Africa’)
#3
Search (#1 AND #2)
#4
Search [#3 AND (‘1990/01/01’ : ‘2017/07/31’) AND Humans]
Stroke
#1
Search (‘Brain infarction’ OR ‘Brain stem infarctions’ OR ‘Cerebral
infarction’ OR ‘Lacunar infarction’ OR ‘Cerebrovascular disease’
OR ‘Cerebrovascular accident’ OR ‘Brain ischaemia’ OR ‘Cerebral
haemorrhage’ OR ‘Cerebral ischaemia’ OR ‘infarct’ OR ‘Cerebral
ischaemia’ OR ‘Brain ischaemia’)
#2
Search (South Africa OR ‘South Africa*’ OR RSA OR Africa, South-
ern OR ‘Southern Africa’)
#3
Search (#1 AND #2)
#4
Search [#3 AND (‘1990/01/01’ : ‘2017/07/31’) AND Humans]