CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 5, September/October 2011
AFRICA
263
Hypertension (WHO/ISH) risk prediction charts for low- and
middle-income countries.
28
These guidelines suggest that antihy-
pertensive therapy is instituted when there is an absolute 10-year
risk of a cardiovascular event of
>
30%.
28
The WHO/ISH risk
charts guidelines exclude an analysis of the impact of adiposity
(as well as HDL cholesterol, and a family history of premature
CVD), and risk in the 20–40 year age category.
As we previously demonstrated that obesity is highly preva-
lent and contributes to cardiovascular damage in urban, devel-
oping communities in South Africa,
18–24
and we have noted that
a significant burden of severe hypertension (BP
≥
180/110
mmHg) exists in participants younger than 40 years, we focused
our analysis on the SAHS/ESH/ESC guidelines which do not
discount these factors. With respect to target-organ changes,
only plasma creatinine concentrations were employed to identify
organ damage, although national guidelines suggest that urinary
microalbumin and electrocardiography criteria also be included,
27
and international guidelines suggest that echocardiography and
the assessment of vascular structure and function be included.
16
The reasons for adopting this approach in the present study are
as follows. National guidelines only advocate the measurement
of urinary microalbumin in patients with DM.
27
Moreover, in the
present study some participants did not provide urine samples.
The high prevalence of obesity (~40%) considerably limited the
value of electrocardiographic criteria for left ventricular hyper-
trophy in this study; and the high prevalence of obesity resulted
in echocardiographic and vascular data (aortic pulse-wave veloc-
ity) being unavailable in a subset of participants.
The combined evidence for decreasing BP to targets lower
than 140/90 mmHg in patients with DM or renal dysfunction is
controversial.
29
Blood pressure was therefore only considered as
uncontrolled if the average clinic reading was
≥
140/90 mmHg
even in participants with DM or renal dysfunction. Moderate
and severe hypertension or moderate and severe increases in
BP values were identified as systolic BP
=
160–179 mmHg or
diastolic BP
=
100–109 mmHg (moderate hypertension) and
systolic BP
≥
180 mmHg or diastolic BP
≥
110 mmHg (severe
hypertension).
16,27
Diabetes mellitus was defined as the use of
insulin or oral hypoglycaemic agents, or a fasting blood glucose
≥
7.0 mmol/l, or a post-prandial glucose
≥
11.0 mmol/l and an
HbA
1c
value
>
6.1%.
30
Statistical analysis
For database management and statistical analysis, SAS software,
version 9.1 (SAS Institute Inc, Cary, NC) was employed. Data
are shown as mean
±
SD or percentages. Age adjustments were
determined from multivariate regression models and differences
in proportions were identified using Fisher’s exact test.
Results
Table 1 gives the characteristics of the normotensive participants,
the hypertensive patients not receiving therapy, and the hyper-
tensive patients receiving therapy; 23.5% of the participants
were hypertensives receiving antihypertensive drug therapy and
22.6% were hypertensives not receiving therapy. Both untreated
and treated hypertensives were older, and had an increased BMI,
waist circumference and waist-to-hip ratio. A greater proportion
of untreated and treated hypertensives were obese, and either
receiving therapy for DM or had a fasting blood glucose
≥
7.0
mmol/l or a post-prandial blood glucose
≥
11.0 mmol/l and an
impaired blood glucose control (HbA
1c
>
6.1%).
A greater proportion of treated hypertensives had dyslipi-
daemia (total cholesterol
>
6.5 mmol/l, or LDL cholesterol
>
4.0 mmol/l, or HDL cholesterol
<
1.0 mmol/l in men and
<
1.2 mmol/l in women). Only 14.6% of participants smoked.
Few participants had pre-existing cardiovascular disease. A
greater proportion of treated hypertensives had slightly elevated
creatinine concentrations (115–133
μ
mol/l in men and 107–124
μmol/l in women).
Table 2 shows BP values, BP control rates and the severity of
high BP in normotensive participants, hypertensive patients not
receiving therapy, and hypertensive patients receiving therapy.
Both the hypertensives not receiving therapy and the hyperten-
sives receiving therapy had markedly higher BP values than the
normotensive participants, even after adjustments for age. The
untreated hypertensives had higher BP values than the treated
TABLE 1. CHARACTERISTICS OF STUDY PARTICIPANTS
Normo-
tensives
Untreated
hypertensives
Treated
hypertensives
Number
554
233
242
Age (years)
33.8
±
14.5 50.4
±
15.9* 60.9
±
11.9*
% female
66.3
55.4
74.0
Body mass index (kg/m
2
)
27.1
±
7.4 30.6
±
7.5* 33.8
±
7.9*
% overweight/obese
21.7/30.7 24.0/51.1* 26.0/61.2*
Waist circumference (cm)
83.8
±
14.7 94.1
±
15.4* 100.3
±
13.9*
Central obesity (%)
31.0
50.5*
70.0*
Waist-to-hip ratio
0.80
±
0.09 0.87
±
0.11* 0.88
±
0.10*
Regular tobacco intake
(% subjects)
15.0
21.5
7.0
Regular alcohol intake
(% subjects)
21.7
27.5
17.4
% with diabetes mellitus
3.1
9.9*
30.2*
% with dyslipidaemia
19.7
24.9
30.6*
% with CVD
4.7
2.6
2.5
% with elevated serum
creatinine
0.9
3.0*
7.4*
CVD: cardiovascular disease. *
p
<
0.001 vs normotensives.
TABLE 2. BP, CONTROL OF BPAND SEVERITY OF BP
Normo-
tensives
(
n
=
554)
Untreated
hypertensives
(
n
=
233)
Treated
hypertensives
(
n
=
242)
BP values
Systolic BP (SBP) (mm Hg)
116
±
11 151
±
20*
†
143
±
23*
Diastolic BP (DBP) (mm Hg)
77
±
8
97
±
10*
†
89
±
13*
Age-adjusted SBP (mm Hg)
120
±
17 148
±
16*
†
136
±
18*
Age-adjusted DBP (mm Hg)
78
±
11 96
±
10*
†
88
±
11*
Control rates
% uncontrolled SBP
0
66.1*
51.2*
% uncontrolled DBP
0
85.0*
47.5*
% uncontrolled SBP and DBP 0
100.0*
64.1*
Severity of increased BP
% with stage I BP
‡
0
57.5*
40.1*
% with stage II BP
‡
0
27.0*
14.0*
% with stage III BP
‡
0
15.5*
9.9*
‡
See text for definitions. *
p
<
0.0001 vs normotensives.
†
p
<
0.0001 vs
treated hypertensives.
