CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 2, March 2012
108
AFRICA
its determinants in geographically separated black populations.
112
After a baseline risk-factor survey from 1995 to 1999, a follow-
up component was initiated in three participating countries,
including Nigeria. The five to seven years of follow up provided
information regarding changing patterns of weight and blood
pressure.
36,59
The two-year follow-up data have already identified
blood pressure as a significant determinant of all-cause mortal-
ity, with a 60% greater risk associated with each 20 mmHg
higher diastolic blood pressure.
60
In a cohort of 528 university students in Zimbabwe, Somova
assessed some psychological predictors and related them to
incident hypertension and trajectory of blood pressure variables
during a four-year follow-up period.
105
In multivariate analysis,
these psychological factors were significant predictors of hyper-
tension. Four hospital studies from four countries totalling 4 488
participants have focused on blood pressure changes under treat-
ment or no treatment, incidence of hypertension, and other health
effects of higher-than-optimal blood pressures.
33,40,48,91,92
Two of
these studies (1 186 participants) were conducted in pregnant
women.
33,40
Glucose exposure and diabetes control
: 10 studies on diabetes
mellitus or glucose tolerance status in relation to new onset of
diabetes, changes in blood glucose levels, incidence of diabetes
complications, and all-cause mortality during follow up were
found. Three were community-based studies of incident diabetes
according to baseline status for glucose tolerance.
31,39,42,45,87
In the Hindu community study in Tanzania, blood glucose and
blood pressure levels improved within four years of follow up, an
improvement that investigators ascribed to community action.
42
Over a longer period of follow up (10 years) of a South African
Indian cohort, Motala found a 0.95% annual rate of progres-
sion to diabetes.
45
Two-hour post-load glucose, body mass index
and obesity were baseline predictors of incident diabetes in this
study. Jackson
31
earlier had reported on the five-year incidence
study of Tamilian Indians first examined in Cape Town in 1965.
In Tanzania, at the diabetes clinic of the Muhimbili Medical
Center in Dar es Salaam, McLarty and his colleagues
38,101,103
monitored a group of individuals with type 1 and type 2 diabetes
from clinical diagnosis between 1981 and 1987, to approxi-
mately seven years. The death rate during follow up of the initial
cohort of 1 250 individuals was 22%; 24% of these deaths were
due to cardiovascular and renal causes. Insulin treatment was
strongly associated with death. A sub-cohort of 793 participants
was also monitored for the incidence of hypertension.
102
The
change in body mass index was the main predictor of increas-
ing systolic blood pressure. Relating data from this study to the
catchment area’s population of the study hospital, the incidence
of type 1 diabetes was ascertained.
104
The biggest hospital cohort of individuals with diabetes was
from the Yekatit 12 Hospital diabetes clinic registry in Addis
Ababa.
34,35
By 1990, this clinic had registered 1 699 patients first
diagnosed with any type of diabetes mellitus after 1969, except
for 204 patients who were lost to follow up. Their follow up
over varying durations has provided information relating to the
incidence of a range of diabetes complications and mortality.
35
Trajectories of other risk factors such as body mass index and
blood pressure variables, as predictors of survival, were alluded
to in this study.
47
Keeton
69
monitored a cohort of 62 individuals with type 2
diabetes in Cape Town, South Africa for renal outcome over a
12-year period. In this high-risk group at baseline, the death rate
during follow up was 79%, with one-third of these deaths being
related to chronic renal failure. The study found a correlation
between deteriorating kidney function and blood pressure vari-
ables. Varying time to event was not accounted for in the data
analysis.
Smoking exposure:
gold miners in South Africa are legally
required to have an initial and a yearly medical examination at
the Medical Bureau for Occupational Diseases (MBOD). The
registers of the MBOD were prospectively utilised in evaluating
the risk of occupational diseases and other entities, including
cardiovascular disease-related risk factors.
43,63,67
A major advan-
tage of this cohort was the completeness of data collected. The
contribution of exposure to smoking to the risk of disease has
been one of the major focus points of this cohort.
64-66
Lipid variables, dyslipidaemia and adiposity
: lipid variables
were assessed along with other risk factors in some studies.
In the Hindu study of glucose tolerance in Dar es Salaam, no
significant difference was found between the baseline and four-
year average levels of total cholesterol and triglycerides and body
mass index.
42
A cohort of 49 individuals with familial hyper-
cholesterolaemia was followed in South Africa over a 13-year
period in relation to the natural history, including cardiovascular
outcomes.
30
CVD accounted for 82% of the 11 deaths registered.
Survivors displayed an array of cardiovascular lesions.
Non-cardiovascular cohorts with potential cardiovascular appli-
cation
: the Africa Centre Demographic Information System
(ACDIS) cohort was started in 2000 in KwaZulu-Natal, South
Africa.
113
It was established to describe the demographic, social
and health impacts of the HIV epidemic in a population going
through a health transition, and to monitor the impact of inter-
vention strategies on the epidemic. As of June 2006, 85 855
participants from approximately 11 000 households have been
under surveillance. Blood pressure variables, weight and height
have been measured for women from 15 to 49 years and men
aged 15 to 54 years. Outcomes monitored included death. There
is an opportunity within this cohort to relate baseline blood
pressure variables and anthropometric measurements to incident
all-cause and cause-specific deaths.
Discussion
The sub-Saharan African region is in health transition as high
blood pressure, high cholesterol levels and tobacco usage
are already among the top risk factors of the CVD epidemic.
Empirical data demonstrate that lifestyle modification and early
diagnosis are critical for prevention of CVD. The epidemic poses
an enormous socio-economic burden and will cripple the region.
Evidence from around the world suggests that major determi-
nants of cardiovascular diseases have been identified. These
determinants are consistent across populations and regions
and may not need to be ‘rediscovered’ in sub-Saharan Africa.
10
However, as recognised by other investigators,
114
a better under-
standing of their epidemiology in SSA ‘will permit the develop-
ment of more effective public health interventions to forestall a
future epidemic of CVD’.
