CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 5, June 2013
182
AFRICA
was a statistically significant relationship between hypertension
and the different socio-professional categories, except for self-
employed, privately employed and volunteer participants (
p
=
0.0031).
Diabetes was detected in 16.5% (13.8–19.6%) of the
participants with HTN and in 5.2% (3.8–7.1%) of participants
without HTN [
p
=
0.023, OR
=
0.32 (0.21–0.47)]. Moreover,
HTN was more frequent in participants with diabetes [73%
(65.1–79.9%)] than in those without diabetes [43% (40.1–
45.6%),
p
<
0.0001, OR
=
3.59 (2.46–5.25)].
Other risk factors associated with HTN were dyslipidaemia
in 71.1% (67.5–74.6%) of participants with HTN versus 59%
(55.5–62.5%) in non-HTN participants (
p
<
0.001), physical
inactivity [48.5% (43.9–52.1%) vs 40.2% (36.3–44.5%),
p
<
0.001] and abdominal obesity [47.3% (43.5–51.2%) vs 21.2%
(18.4–24.3%),
p
<
0.001].
HTN was more frequent in the case of a past history of
smoking (50.8%) (41.8–59.7%) than in passive exposure (44.8%)
(40.9–48.8%) and cigarette users (33.7%) (23.7–44.9%). A
medical history of stroke was more frequent in participants with
HTN (2.7%) (1.7–4.4%) compared with those without HTN
(0.5%) (0.2–1.4%) (
p
<
0.001). HTN was correlated with the
creatinine level (
p
<
0.05) (Fig. 3). The mean clearance rate of
creatinine gradually decreased with the duration of hypertension
(Fig. 4) (
p
=
0.26).
Discussion
In order to gather data on the frequency of HTN and associated
risk factors in urban Saint Louis residents, we carried out a
population-based, cross-sectional survey with a methodology
closed to the WHO STEPwise approach. We found a significant
increase in the prevalence of HTN.
A previous study performed in the same region in 1970
found a prevalence of 4.9% in a rural population, whereas the
prevalence was 7% in an urban population. Even though the
methodology (HTN if BP
≥
160/95 mmHg) in this study was not
similar to ours, our results suggest a significant increase in the
prevalence of HTN since 1970.
8
Moreover, Kane
et al
. in 1995
found a prevalence of 20.2% with a methodology very similar
to ours.
5
In the sub-Saharan African region, two studies have
reported a median prevalence of 28%, with a regional variation
ranging from 15 to 38.6%.
1,9
Changes in lifestyle may be the
major factor leading to this increasing prevalence of HTN and
other cardiovascular risk factors.
9-11
While we have not found significant associations between
HTN and level of education, it should be noted that previous
studies found such an association. The ENNS trial found than
HTN was twice as frequent in people with a primary level of
education than in those who had secondary or postgraduate
levels of education. This difference was higher in women: the
risk of HTN was four-fold higher in less-educated women than
in those with higher levels of education.
2
The same observation
was made in Brazzaville, Congo.
9
TABLE 1. CHARACTERISTICS OF THE STUDY POPULATION (
n
=
1 424)
Female
Male
Total
p
Sample size
983
441
1424
Age (years), mean (SD)
44.2 (17.2) 41.7 (18.9) 43.4 (7.8)
0.016
Weight (kg), mean (SD)
71.7 (17.9) 67.6 (13.6) 70.5 (16.7)
<
0.001
Height (cm), mean (SD)
163.3 (8.3) 174.9 (8.5) 166 (9.9)
<
0.001
Waist circumference (cm), mean (SD) 87.4 (16.5) 81.2 (46.8) 84.6 (15.9)
0.0003
Systolic BP (mmHg), mean (SD)
131.1 (28.7) 131.9 (22.3) 131.2 (27.8)
0.893
Diastolic BP (mmHg), mean (SD)
86.7 (24.5) 82.4 (22.4) 85.4 (22.4)
0.0001
BMI (kg/m
2
), mean (SD)
27 (7.2) 22.1 (16.2) 25.5 (6.7)
<
0.001
SD: standard deviation
TABLE 2. PREVALENCE OF CARDIOVASCULAR RISK FACTORS
IN THE STUDIED POPULATION (
n
=
1 424)
Risk factors
Prevalence, % (95% CI)
Hypertension
46 (43.4–48.6)
Abdominal obesity
33.2 (30.8–35.7)
Obesity (BMI
>
30 kg/m
2
)
23 (18.1–28.2)
Tobacco smokers
5.8 (4.7–7.2)
Physical inactivity
44.4 (40.2–49)
Diabetes
10.4 (8.9–12.1)
Raised cholesterol (
>
2 g/l )
36.3 (33.8–38.9)
Raised LDL cholesterol (
>
1.6 g/l )
20.6 (18.5–22.8)
Low value of HDL cholesterol
41.9 (39.4–44.5)
Metabolic syndrome
15.8 (14–17.8)
BMI: body mass index, CI: confidence interval.
TABLE 3. PREVALENCE OF HYPERTENSION IN
SOCIO-PROFESSIONAL CATEGORY
Number
Hypertension (%)
p
Official
71
36.6
1
Private
72
25
0.13
Self employed
496
48.2
0.06
Volunteer
9
22.2
0.39
Housewife
528
50.9
0.023
Student
130
10
<
0.001
Unemployed
35
57.1
0.045
Retired
83
81.9
<
0.001
Fig. 2. Prevalence of hypertension by age (
n
=
655).
100
80
60
40
20
0
15–24
25–34 35–44 45–54 55–64
>
65
Age category
Prevalence of hypertension (%)
88.0%
74.4%
58.0%
33.0%
23.0%
13.0%
Fig. 3. Prevalence of hypertension by creatinine clear-
ance rate (
n
=
655).
100
50
0
>
90
61–90
31–60
15–30
Creatine clearance
Frequency (%)
88%
60%
50%
34%
