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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 3, May/June 2021
AFRICA
159
For CHD, the exclusion of Shisana
et al
. from the meta-
analysis resulted in a slightly higher effect estimate, from 4.3
to 4.8. Removing Shisana
et al.
also resulted in a significant
reduction in the level of heterogeneity, from 96 to 66%, which is
a moderate level of heterogeneity.
To assess whether excluding studies that assessed gender-
specific prevalence affected the overall prevalence effect estimate,
the South African Demographic Health Survey (SADHS)
24
and
Shisana
et al
.
27
were excluded for stroke, and Arokiasamy
et al
.,
28
SADHS
24
and Shisana
et al
.
27
were excluded for CHD. The overall
prevalence effect estimate went down slightly for stroke from 1.29
to 1.26, and went up for CHD, from 4.29 to 4.63. The heterogeneity
improved to 82% for CHD by removing those studies. For stroke,
heterogeneity did not change much, indicating that the inclusion of
these two studies did not make a significant difference.
Only SADHS 1998 reported a national incidence rate of
CHD and stroke for men and women. For men, the incidence
rates were 135 and 795 per 100 000 people for CHD and stroke
respectively, and 234 and 1 744 for women. No other studies
looked at incidence rates for either disease at a national level.
Discussion
The overall national prevalence of CHD and stroke in South
Africa between 1990 and 2017, determined from five and seven
studies, respectively, was low. This was also low compared
to the crude prevalence rate of stroke of 387.93 per 100 000
in Africa.
30
The crude prevalence of stroke was 243 cases per
100 000 population in those aged 15 years or more, and 300 cases
per 100 000 population in a rural community in north-east South
Africa.
10
Another report estimated that 842 incident cases of
stroke occurred in South Africa from 2007 to 2011.
10
Our research has highlighted only one study on incidence
and very few studies on the prevalence of CHD and stroke in
South Africa. Given the high mortality burden, we would have
expected a larger body of literature on these topics. Furthermore,
there were insufficient data to estimate the prevalence of CHD or
stroke by urban–rural residence.
Differential exposures to CVD risk factors by urban–
rural residence, among other factors, is likely to influence the
development of CHD and stroke. For example, poorer diets
with higher caloric intake, greater sedentary behaviour and lower
physical activity levels in urban compared with rural residents
lead to higher rates of obesity, diabetes and hypertension
in urban subjects. The uptake of these unhealthy lifestyle
behaviours, together with the above cardiometabolic conditions,
contribute to a greater risk for developing CHD and stroke in
urban versus rural residents. Therefore, more epidemiological
research needs to be conducted in both urban and rural areas,
by gender and across population groups, because differential
exposures to risk factors is likely to influence the burden of CHD
and stroke.
31
Detailed and accurate information across these
subgroups on the incidence and prevalence of CHD and stroke is
essential for the prevention and management of CVDs.
32
Although some studies have found that self-reported estimates
were congruent with clinically measured estimates of disease,
33,34
others found that there were major differences between self-
reported measures and actual clinical measurements.
35,36
There
is also evidence that even though rates may seem low for CHD
and stroke, this may be due to poor ascertainment or because
it is under-diagnosed.
37,38
This could be a contributory factor to
the low rates found in this study. There is, therefore, a need to
determine prevalence estimates based on clinical assessments
rather than relying on self-reported estimates, as this will likely
provide a more accurate picture.
Although resting 12-lead electrocardiographs (ECGs) are
available and inexpensive diagnostic tools for CHD, they have
limited sensitivity and specificity for the diagnosis of acute
coronary syndromes.
39
ECGs are inadequate screening tests
in research settings where reproducibility is of paramount
importance.
40
A standardised system, for example, the Minnesota
coding system, is required when conducting epidemiological
studies to ensure uniformity of interpretation. However, this has
its disadvantages and may lead to over-reading.
40
To determine the true burden of stroke, community-based
studies that include brain imaging for accurate classification
of stroke would be optimal, but such studies are expensive and
challenging to conduct, particularly in low-resource settings.
31,41
A possible solution may be to establish well-structured CHD
and stroke registries nationally. However, such an undertaking
requires much effort and infrastructure costs to ensure good
co-ordination and communication across centres.
42
Furthermore,
there needs to be continuous monitoring and quality control to
optimise data capturing.
The limitations of this review are that the 12 included studies
were based on self-reported conditions and only one study was
found that estimated incidence rates in CHD and stroke. Also,
due to the small number of studies found, we were unable to
conduct meaningful subgroup analyses. Only English language
studies were included in this review. Grey literature, pre-prints
and theses were also not included. The strength of this study was
that we were able to provide pooled prevalence estimates of CHD
and stroke in South Africa, which to date has not been done.
Conclusions
The findings of this review quantify the overall national
prevalence of CHD and stroke, which was found to be low
and may be due to the absence of the relevant evidence in the
literature. This highlights the need for reliable and nationally
representative data, as well as data by urban–rural residence,
population group and gender, to identify high-risk, vulnerable
communities. This can be achieved by the introduction of well-
structured registries to correctly identify the burden of CHD
and stroke in South Africa, which in turn could inform health
policies and the delivery of appropriate healthcare services.
This study was funded by the South African Medical Research Council
(SAMRC) with funds from the National Treasury under the SAMRC
Computative Intramural Research Fund (SAMRC-RFA-IFF-02-2016).
References
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World Health Organization. Cardiovascular diseases – Fact sheet N 317.
World Health Organisation. Available from: www.who.int/mediacentre/
factsheet/fs317/en/. Updated 2016 June.
2.
World Health Organization. World health statistics 2012. Geneva: World
Health Organization, 2012.
3.
Strong K, Mathers C, Leeder S, Beaglehole R. Preventing chronic diseases:
how many lives can we save?
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2005;
366
:1578–1582.