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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 25, No 6, November/December 2014
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AFRICA
decade 40s and above (Fig. 3), consistent with post-menopausal
hormonal changes related to the observed increase in androgen
levels post menopause.
32
Knowing that obstructive sleep apnoea/hypopnoea syndrome
(OSAHS) is a risk factor for developing HTN, post-menopausal
women with OSAHS showed a higher prevalence of HTN when
compared to those without OSAHS and to all pre-menopausal
women.
33
It was also noted in the same study that among females
with OSAHS, post-menopausal women had higher SBP and
DBP averages when compared to pre-menopausal women. This
may have been due to falling oestrogen levels in post-menopausal
women, because oestrogen decline causes a rise in BP via the
activation of the renin–angiotensin system, which in turn explains
the observed higher plasma renin levels in post-menopausal
females compared to males and pre-menopausal females.
32
Furthermore, endothelin levels are higher in post-menopausal
females, which explains in part the observed higher BPs, since
endothelin causes sodium re-absorption, which in turn causes
higher BP.
32
All of these factors make increasing age a risk factor
of acquiring HTN in females, considering also the observation
that about 60% of females aged
>
65 years are hypertensive.
32
HTN in Sierra Leone and the Gambia
This study highlights the high prevalence of HTN in the
Gambia and Sierra Leone. HTN seems to be highly prevalent
as a CVD in the sub-Saharan African region,
19
and may be
rising over time. In 2006, a cross-sectional study in Uganda
revealed that 252 individuals out of the 842 participants (29.9%)
were hypertensive.
30
In 2007–2008, a study in Kenya found that
50.1% of 4 396 subjects were hypertensive.
1
In 1991–1995, HTN
prevalence in rural and urban Cameroon was 17.3%; however, in
2003, the rate rose by an additional 7.3%.
34
HTN in Sierra Leone was reviewed in several studies. Between
1983 and 1992, HTN accounted for about 7.5% on average of all
deaths in Freetown, the capital of Sierra Leone.
35
A retrospective
study, published in 1993, showed that among 87 subjects, 59
individuals were hypertensive.
36
HTN prevalence, according to the HTN definition of
≥
160/95 mmHg, was measured in four Sierra Leonean towns
and villages. In 1998, in Njala Komboya and Kychum, HTN
prevalence was 24.8 and 17.6%, respectively.
37
Similarly, in 1999,
HTN prevalence was 23.4 and 14.7% in Freetown and Port Loko,
respectively.
38
Recently, in Bo in 2009, 25.2% of 3 944 individuals
aged
≥
15 years old were hypertensive according to the HTN
definition of
≥
140/90 mmHg; however, the study showed no
difference in BPs between males and females.
29
HTN prevalence
by calendar year seems to agree with our results, showing that
SBP and DBP LSmeans tended to be higher in the later years
(2003 and 2009) than in the earlier years (2001 and 2002).
Several studies reviewed HTN in the Gambia. In 1996–1997,
the HTN prevalence, according to the definition of
≥
160/95
mmHg, was 7.1%, whereas by 1998, it rose to 10.2%, an
increase of 3.1% in a year.
34
According to the HTN definition
in the current study (
≥
140/90 mmHg), van der Sande showed
in 1997 that 24.2% of 6 048 individuals in the Gambia were
hypertensive.
23
Although the prevalence of HTN seems to be
high in the Gambia, a study in 2001 pointed out that HTN
prevalence in the Gambia varies with the specific geographical
area in the country.
39
These results show the high prevalence rate of HTN in the
Gambia and Sierra Leone. Comparatively, in our current study,
the HTN prevalence rate in both countries combined was 46.2%
among females (
n
=
1 399), 43.2% among males (
n
=
1 215), and
44.8% overall (
n
=
2 614).
Influence of low SES
One major dilemma in sub-Saharan Africa is the low SES of
countries in the region, including the Gambia and Sierra Leone.
It was estimated that the total number of hypertensive adults
in developing countries in 2000 was 639 million, compared to
333 million in developed countries,
20
which is a result of the
difference in SES.
18
The low SES establishes a variety of factors contributing
to the prevalence of HTN, including a low HTN treatment
rate, low levels of education and awareness, high salt and low
potassium intakes, as well as an increased stress level. All these
factors contribute directly or indirectly to the HTN prevalence
rate among countries in the sub-Saharan African region.
18,34
Evidently, low SES was linked to high BP means, with a stronger
effect on females than males.
40
HTN treatment and SES
The treatment rate of a chronic disease depends on several
factors, including the cost of the treatment associated with
the disease. As mentioned, the SES of Sierra Leone and the
Gambia is low and this may contribute to lack of availability of
antihypertensive treatment.
18
A study in Kenya showed that only
15% of hypertensive individuals were able to obtain treatment
for HTN.
1
A low SES contributed to the government not having
adequate amounts of medications to distribute among patients.
In a 1999 survey in Cape Town, South Africa, 15.5% of
patients reported that during filling prescriptions, insufficient
medication was supplied.
41
A low SES also contributed to
individual patients not having enough income to pay for the
medications. In the Gambia, in 2006, the rate of unemployment
was high.
42
Therefore, the inability to obtain medication was a
factor contributing to the high HTN prevalence rate.
Education levels and SES
The awareness of HTN was previously correlated with the
prevalence rate of the disease.
22
This awareness is usually
provided by schools as well as public healthcare facilities.
Establishment of schools has been difficult in societies with low
SES. Concerning school education, in the Gambia, a research
study showed that 10 and 56% of women aged 10–25 (
n
=
50) and
35–50 (
n
=
50) years, respectively, were unable to read, whereas
34% of 50 males aged 35–50 years were unable to read.
42
A
study in Tanzania also pointed out that SBP was associated with
education, which in turn was associated with SES; the higher the
SES, the lower the SBP.
21
Establishment and funding of public healthcare facilities,
such as medical schools and nursing schools, has also been
difficult in low SES countries. In 2000–2010, there were 0.4
physicians and 5.7 nurses and midwives per 10 000 individuals
in the Gambia, while in Sierra Leone, there were 0.2 physicians
and 1.7 nurses and midwives per 10 000 individuals. On the other