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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.