Basic HTML Version
14
VOLUME 9 NUMBER 1 • MARCH 2012
RESEARCH ARTICLE
SA JOURNAL OF DIABETES & VASCULAR DISEASE
A
collaboration between the University of Stellenbosch and the
Cape Peninsula University of Technology, investigating the
30-year cardiovascular risk profile of South Africans, has recently
been published.
1
In particular, South African individuals of mixed
ancestry with non-diabetic hyperglycaemia and undiagnosed and
self-reported diabetes were assessed.
The urban community of Bellville South, Cape Town provided
583 participants without a history of cardiovascular disease, who
were eligible for lifetime estimation of risk for cardiovascular dis-
ease. High cardiovascular disease risk (> 20%) was evident in nor-
moglycaemic and younger subjects (under 35 years). Significant
predictors of cardiovascular disease were found to be sibling his-
tory of diabetes, and levels of triglycerides, low-density lipoprotein
cholesterol and glycated haemoglobin (
p
< 0.001).
High lifetime risk of cardiovascular disease in South
Africans of mixed ancestry: findings of the Bellville,
South Africa pilot study
‘The high lifetime risk in normoglycaemic and younger subjects
may be considered a warning that cardiovascular disease might
take on epidemic proportions in the near future in this country’
developed for the assessment of cardiovascular disease risk over a
10-year period in general populations. The 10-year time frame of
these models has faced criticism as the lifetime risk may be high,
whereas the 10-year risk prediction may be low.
An algorithm allowing for 30-year risk assessment has recently
been developed. Although this provides a lifetime risk level, criti-
cism is that this method oversimplifies the risk and may also lead
to overuse of medication. This method is additionally limited by
patient-specific issues, such as socio-economic status and ethnic-
ity.
Individuals of mixed-ancestry from the Bellville South commu-
nity between the ages of 35 and 65 years were randomly selected
for the cohort. Trained personnel administered a questionnaire
designed to retrospectively obtain information on lifestyle factors
such as smoking and alcohol consumption, physical activity, diet,
family history of cardiovascular disease and diabetes, as well as
demographic considerations. A detailed drug history was obtained
and clinical measurement included height, weight, hip and waist
circumferences, body fat measurements and blood pressure.
Other than self-reported diabetic subjects, all participants under-
went a 75-g oral glucose-tolerance test, with fasting blood glu-
cose determinations in all participants. Blood assessments included
plasma glucose, glycosylated haemoglobin (HbA
1c
), low-density
lipoprotein cholesterol, high-density lipoprotein cholesterol and
triglycerides.
Relationship between dysglycaemia and
cardiovascular risk
Previous studies of the South African population have indicated
marked geographical and ethnic variations in the prevalence of
diabetes. The South African Indian popula-
tion has the highest incidence of diabetes,
followed by individuals of mixed ancestry.
Mortality from cardiovascular disease is two-
to four-fold higher in individuals with type 2
diabetes mellitus. The relationship between
dysglycaemia and cardiovascular disease is
linear, and sometimes starts below the diag-
nostic level of diabetes.
The aim of this pilot study was to assess
the lifetime cardiovascular disease risk in the
mixed-ancestry population of South Africa
in individuals with non-diabetic hypergly-
caemia, undiagnosed diabetes, known dia-
betes and normoglycaemia.
Cardiovascular risk assessment:
10- vs 30-year models
Mathematical equations incorporating major
cardiovascular disease risk factors (age,
gender, high blood pressure, smoking, dys-
lipidaemia and diabetes), as well as models
from the Framingham Heart Study and the
UK Prospective Diabetes Study have been
Table 1.
Cardiovascular disease risk factors used in the equation in different age groups.
Age groups (years)
CVD risk factor
20–30
31–40
41–50
51–60
% males
9.5
16.7
36.50
37.3
% BMI < 25 kg/m
2
50
22.95
30.81
20.71
% BMI ≥ 25, < 30 kg/m
2
29.17
24.59
25.12
29.80
% BMI ≥ 30 kg/m
2
20.83
52.46
44.08
49.49
SBP (mmHg)*
112.7 ± 13.9
113.9 ± 13.7
119.4 ± 17.1
125.6 ± 17.6
TC (mmol/l)*
4.7 ± 1.1
5.1 ± 1.0
5.4 ± 1.1
6.0 ± 1.2
HDL-C (mmol/l)*
1.2 ± 0.26
1.2 ± 0.37
1.3 ± 0.35
1.3 ± 0.36
% smoking
63.27
49.18
47.42
44.72
TRTBP
10.42
12.30
25.59
47.45
Diabetes status
% IFG
2.04
4.96
5.63
3.52
% IGT
2.04
13.22
15.02
20.60
% undiagnosed DM 4.08
5.79
13.62
18.59
% self-reported DM 0
5.79
6.57
14.07
Lipid full (%)
#
8.5 ± 6.9
19.4 ± 13.0
35.1 ± 17.6
56.6 ± 18.2
*Replicated measurements,
#
Mean ± standard deviation.
CVD, cardiovascular disease; BMI, body mass index; SBP, systolic blood pressure; TC, total cholesterol;
HDL-C, high-density lipoprotein cholesterol; TRTBP, treatment for blood pressure; IFG, impaired fasting
glucose; IGT, impaired glucose tolerance, DM, diabetes mellitus.