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VOLUME 13 NUMBER 1 • JULY 2016
15
SA JOURNAL OF DIABETES & VASCULAR DISEASE
RESEARCH ARTICLE
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 many
other cardiovascular risk factors may soon appear in these patients
as time goes on.
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 in our study was however lower than that reported among
Caucasians. A report from Spain 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
occurrence of the metabolic syndrome and suggested that African
blacks are at lower risk than whites and Indians.
20
It has been suggested that black Africans have lower serum
lipoprotein and apolipoprotein levels than their Caucasian
counterparts.
21
Blacks have also been reported to have a lower blood
total cholesterol level when compared to whites and a comparably
higher level of HDL-C, especially among females. This was thought
to be due to the dietary pattern among blacks, which is particularly
related to low dietary fat intake, especially among Nigerians.
21
This
and possible genetic reasons may be responsible for the difference
in frequency of occurrence 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 increases the risk of
cardiovascular events for these groups of patients.
22-24
A possible
reason for the increased frequency of clustering of cardiovascular
risk factors among hypertensive subjects has been suggested to
be due to similar pathogenic pathways underlying the clustered
risk factors.
25,26
These include insulin resistance, hyperinsulinaemia,
inflammation and hyperadrenergic state.
Hypertensive subjects with the metabolic syndrome were
significantly older than their counterparts without the metabolic
syndrome. There were more female than male hypertensives
with the metabolic syndrome. Several studies have documented
increased prevalence as age increases, and more so among
females.
27-31
However, reports are not consistent as other reviews
have found marginal increase in prevalence among males.
27
These
gender-related differences may be due to differing work-related
activities, and cultural views on body fat and work-related activities.
The increasing prevalence of the metabolic syndrome may not be
implausible, since many of its components increase in prevalence
with age.
Hypertensives with the metabolic syndrome seem to have 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 interval, 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 levels
was the commonest pattern among hypertensive subjects with the
metabolic syndrome, followed by the combination of hypertension,
obesity and impaired fasting plasma glucose levels. Hypertensives
with the metabolic syndrome had higher fasting plasma glucose
levels than those without the metabolic syndrome. Impaired fasting
plasma glucose levels have been associated with an increased
likelihood of developing diabetes mellitus. These hypertensive
subjects therefore require intensive cardiovascular evaluation and
care to reverse the increased tendency towards 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 regard 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
cardiovascular disease prevalence.
Conclusion
This study shows that prevalence of the metabolic syndrome among
newly diagnosed hypertensive subjects is high and is influenced by
demographic and clinical factors such as age, gender, systolic blood
pressure and body mass index. These observations raise major
clinical and public health concerns, which include an inevitable
increase in the prevalence of cardiovascular diseases due to the
increasing frequency of hypertension and other cardiovascular risk
factors in the population.
The cost of management of cardiovascular disease is enormous,
which imposes a serious economic burden, especially on developing
countries. As urbanisationandwesternisation increase, the clustering
Table 3.
Clinical characteristics of hypertensive subjects with and with-
out the metabolic syndrome
Hypertensives Hypertensives
with MetS without MetS
Parameter (
n
= 44) (
n
= 96)
p
-value
Age (years)
57.22 ± 9.65
53.52 ± 10.58
< 0.05*
Gender,
n
(%)
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*
MetS, metabolic syndrome; BMI, body mass index; SBP, systolic blood pressure;
DBP, diastolic blood pressure; LVH, left ventricular hypertrophy. *Statistically
significant.
Table 4.
Pattern of combination of risk factors among subjects with the
metabolic syndrome
Combination of risk factors
Number (%)
Hypertension + obesity + low HDL-C 29 (20.7)
Hypertension + obesity + IFG
5 (3.6)
Hypertension + obesity + hypertriglyceridaemia
3 (2.1)
Hypertension + low HDL-C + hypertriglyceridaemia 2 (1.4)
Hypertension + low HDL-C + IFG
2 (1.4)
Hypertension + hypertriglyceridaemia + IFG
1 (0.7)
Hypertension + hypertriglyceridaemia + IFG
1 (0.7)
Hypertension + obesity + low HDL-C
+ hypertriglyceridaemia + IFG
1 (0.7)
HDL-C, high-density lipoprotein cholesterol; IFG, impaired fasting glucose.