SA JOURNAL OF DIABETES & VASCULAR DISEASE
RESEARCH ARTICLE
VOLUME 7 NUMBER 3 • SEPTEMBER 2010
109
black hypertensives in South Africa documented a frequency of
occurrence of 33.5%. Therefore, about a third of newly diagnosed
subjects with hypertension already have at least two other major
cardiovascular risk factors, and are already at increased risk of
developing cardiovascular events. It is also more likely that other
cardiovascular risk factors might appear in these patients over
time.
6,10
Therefore, newly diagnosed subjects with hypertension
should be adequately screened for other cardiovascular risk
factors so as to reduce the burden of cardiovascular disease in the
population.
The prevalence of the metabolic syndrome among hypertensive
subjects was however lower than that reported among Caucasians.
A report fromSpain shows that 52%of a hypertensive cohort fulfilled
the NCEP ATP III criteria for diagnosing the metabolic syndrome.
19
Some authors have linked race with the frequency of occurence
of the metabolic syndrome and suggested that African blacks are
at a lower risk than whites and Indians.
20
It has been suggested
that black Africans have lower serum levels of lipoproteins and
apolipoproteins than their Caucasian counterparts.
21
Blacks have
also been reported to have a lower blood level of total cholesterol
when compared to whites, and a comparably higher value of HDL
cholesterol, especially among females. This was suggested to be
due to the dietary pattern in blacks, which is particularly low in
dietary fat, especially among Nigerians.
21
This and a possible genetic
difference may be responsible for the difference in frequency of
occurence of cardiovascular risk factor clustering among black and
Caucasian subjects.
10,22
Hypertension has been closely associated with many other
cardiovascular risk factors. This clustering of risk factors increases
the risk of cardiovascular events for these groups of patients.
22-24
The suggested reason for the increased cardiovascular risk
factors among hypertensive subjects is the similar pathogenetic
pathways underlying the clustered risk factors.
25,26
These include
insulin resistance, hyperinsulinaemia, inflammation and the
hyperadrenergic state.
Hypertensive subjects with the metabolic syndrome were
significantly older than their counterparts without the MS. There
were more female than male hypertensives with the metabolic
syndrome. Several studies have documented increased prevalence
with increased age and the female gender.
27-31
However reports
are not consistent, as other reviews have found marginal increases
in prevalence among males.
27
This gender-related difference may
be due to differing work-related activities, and cultural views on
body fat and work-related activities. The apparent increasing
prevalence of the metabolic syndrome may be real, since many of
the components increase in prevalence with age.
Hypertensiveswith themetabolic syndrome seemto be thosewith
a greater degree of target-organ damage, as indicated by increased
prevalence of left ventricular hypertrophy and cardiomegaly. Left
ventricular hypertrophy is an important pointer to cardiovascular
risk and morbidity. Apart from this, hypertensive subjects with the
metabolic syndrome also had a higher QTc, body mass index and
systolic blood pressure than those without the metabolic syndrome.
QTc prolongation is a non-invasive marker for the development of
arrhythmias and sudden cardiac death.
The combination of hypertension, obesity and low HDL-C was
the commonest pattern among hypertensive subjects with the
metabolic syndrome, followed by the combination of hypertension,
obesity and impaired fasting plasma glucose. Hypertensives with
the metabolic syndrome had higher fasting plasma glucose levels
than those without the metabolic syndrome. Impaired fasting
plasma glucose has been associated with an increased likelihood of
developing diabetes mellitus. These groups of hypertensive subjects
therefore require intensive cardiovascular evaluation and care to
reverse the increased tendency for the development of diabetes
and cardiovascular diseases.
As Africa undergoes an epidemiological transition, the
inevitable increase in prevalence of the metabolic syndrome would
have important implications with respect to the potential rise in
the incidence of ischaemic heart disease and diabetes. Available
evidence suggests that the prevalence of cardiovascular disease
among Nigerians is increasing.
32-34
Therefore it is important to
identify high-risk individuals for target therapy to reduce the overall
prevalence of cardiovascular disease.
Conclusion
This study showed that the prevalence of the metabolic syndrome
among newly diagnosed hypertensive Nigerian subjects was high
Table 4.
Pattern of combination of risk factors among subjects with the
metabolic syndrome
Combination of risk factors
Number
(%)
Hypertension
+
obesity
+
low HDL
29 (20.7)
Hypertension
+
obesity
+
IFG
5 (3.6)
Hypertension
+
obesity
+
hypertriglyceridaemia
3 (2.1)
Hypertension
+
low HDL
+
hypertriglyceridaemia
2 (1.4)
Hypertension
+
low HDL
+
IFG
2 (1.4)
Hypertension
+
hypertriglyceridaemia
+
IFG
1 (0.7)
Hypertension
+
hypertriglyceridaemia
+
IFG
1 (0.7)
Hypertension
+
obesity
+
low HDL
+
hypertriglyceridaemia
+
IFG 1 (0.7)
HDL: high-density lipoprotein, IFG: impaired fasting glucose.
Table 3.
Clinical characteristics of hypertensive subjects with and without
the metabolic syndrome
Parameter
Hypertensives
with MS
(
n
=
44)
Hypertensives
without MS
(
n
=
96)
p
-value
Age (years)
57.22
±
9.65 53.52
±
10.58
<
0.05*
Gender
38 (27.1%)
39 (27.9%)
<
0.05*
Mean BMI (kg/m
2
)
30.15
±
5.27 24.14
±
4.10
<
0.005*
Mean SBP (mmHg)
141.36
±
23.66 130.16
±
29.50
<
0.05*
Mean DBP (mmHg)
86.17
±
18.19 80.97
±
17.54
>
0.05
Hypertensives with LVH
39 (70.9%)
56 (65.9%)
<
0.05*
Mean QTc (msec)
0.42
±
0.03
0.41
±
0.03
<
0.05*
FBS (mmol/l)
4.7
±
1.6
5.6
±
1.2
<
0.05*
BMI: body mass index, SBP: systolic blood pressure, DBP: diastolic blood
pressure, LVH: left ventricular hypertrophy.
*Statistically significant.
