CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 2, March 2012
AFRICA
109
The present review suggests that the magnitude of the burden
of CVD risk factors, their interrelation and how they affect inci-
dent CVD in SSA are less well known. The few available studies
have several methodological shortcomings, including smaller
sample size and accordingly lower statistical power for answer-
ing relevant questions. Furthermore, the significant heterogene-
ity between studies precludes data pooling in the studies or at
individual level to increase the statistical power.
A series of reviews on cardiovascular diseases in SSA has
recently highlighted the importance of and need for local research
on CVDs and how they are currently managed in SSA.
1,10,11,115,116
Current and projected health changes operating in SSA confirm
that these countries are going through the earlier and intermedi-
ate stages of epidemiological transition.
11
This provides a unique
opportunity to probe some of the unexplained period effects in
the epidemic of CVD-associated economic expansion, which
may yield some aetiological clues to their environmental deter-
minants. The natural epidemiological experiments created by
the high prevalence of some chronic infectious diseases (HIV/
AIDS, viral hepatitis, tuberculosis) in SSA provide another
unique opportunity for assessing their contribution to the burden
of CVD.
Efforts to fill the gaps in knowledge on CVD in SSA must be
nested with interventions aimed at translating the current knowl-
edge regarding interventions into practical strategies that will
limit the burden of cardiovascular diseases in this population. In
the absence of relevant data specific to SSA, evidence derived
from other populations has been used to inform cardiovascular
disease prevention initiatives in Africa. This uncritical applica-
tion of recommendations derived from elsewhere to SSA popula-
tions may be inappropriate, as discussed elsewhere.
115
In addition, where in existence, recommendations for cardio-
vascular disease prevention in SSA have not yet embraced the
concept of the global risk approach.
118
It is well known that the
traditional single risk-factor approach to CVD prevention does
not capture the mutifactorial nature of CVD, and the continuum
of risks associated with many risk factors. This approach leads to
the inappropriate assignment of individuals to prevention thera-
pies, and inappropriate health resource allocation, and therefore
must be discouraged in SSA.
Limited resources may be a constraint to the adoption of
global risk tools, particularly those that include laboratory meas-
urements, such as lipid variables, in their calculation. However,
the WHO and other investigators have developed non-laboratory
versions of such tools.
119,120
Although these would require some
recalibration to adjust their performance to the SSA setting, the
use of such tools should be encouraged in SSA, alongside other
CVD prevention strategies. Ultimately, when local cohort data
become available, global risk tools specific to the SSA popula-
tion should be developed, given that recalibration may not be
successful in all circumstances.
Study limitations
The present review has some limitations that are worth mention-
ing. These include our inability to capture data available at only
the country level, such as theses and health reports. By restricting
the review to those articles with an abstract in English, indexed
to two major databases, we have possibly missed some studies
published in other languages and probably not indexed. This
would be the case particularly for publications in French, the offi-
cial language of a number of African countries. We are not aware
of a dedicated online scientific database for these countries.
We did not include in our search strategies terms relating to
early antecedents of CVD, such as obesity, physical activity or
unhealthy eating habits, since we felt that their effects on CVD
are mediated by the other factors accounted for in the review
(those are diabetes mellitus, hypertension and dyslipidaemia).
Similarly, scoring tools such as ‘metabolic syndrome’ and
‘absolute risk tools’ were not included in the search terms, again
as these refer to the combination of those risk factors already
included in the search terms, and their uptake in SSA remains
very limited.
Conclusions
Prospective cohort studies are needed to inform and update
our knowledge regarding the epidemiology of cardiovascular
diseases, and how this changes with time as a result of the natural
history and implementation of preventative strategies. The case
for cohort studies on non-communicable diseases in general in
Africa is available in more detail from Holmes
et al
.
121
Interaction
with investigators in SSA suggests that two limited-scale longitu-
dinal studies on CVDs are in the planning stage in SSA.
The Abuja Heart Study, which started in 2008, will follow
3 000 individuals in Nigeria for five years for CVD outcomes
in relation to socio-economic status.
122
The Prospective Urban
and Rural Epidemiological Study (PURE) is a multinational
observational study of the effects of societal changes on the
burden of chronic diseases, including CVDs.
123
Three SSA coun-
tries (Tanzania, Zimbabwe and South Africa) are involved in
this study. Collectively, these studies will provide future useful,
although still limited knowledge relating the burden of CVD in
SSA.
There is probably no requirement for cohort studies in each
SSA country, for both scientific and feasibility reasons. Filling
the gaps and providing definitive evidence on CVD in SSA may
require only continuous follow up of a diversified population of
sufficiently large size. This will provide for the investigation of
known and putative risk factors, including genetic predisposi-
tion, their interrelationships, and changing patterns with time.
Additionally, it will allow for the quantification of the burden
of CVD within the context of competing health risks, through
exhaustive baseline assessments, including the establishment of
bio-repositories for future investigations. With such a commu-
nity study set up, additional efforts could consist of establishing
multi-centre registers in major SSA hospitals to monitor the
incidence, management and outcomes of patients with specific
profiles, and regularly update prevention strategies.
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