CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 9/10, October/November 2013
348
AFRICA
participants living in all other GPZs had a significantly higher
odds ratio of hypertension, apart from those in the south-west.
Ethnicity data were missing for 58 participants and they were
excluded from this analysis. The prevalence of hypertension
varied by ethnic group, with the highest prevalence being in the
Kanuri group (77.5%) and lowest in the Gbagyi group (25.9%)
(Table 5). Adjusting for age, gender, place of residence and
socio-economic status, the Kanuri, Nupe, Tiv, Fulani, Anang,
Hausa and Edo ethnic groups had statistically significantly
greater odds ratios of hypertension than the ‘other’ group. The
Yoruba group had statistically significantly lower odds ratios of
hypertension than the ‘other’ group.
Discussion
The prevalence of hypertension reported in this survey was
higher than in other smaller studies carried out in Nigeria, where
the prevalence ranged from 20.2 to 36.6%.
15,23-26
However the
age range of respondents as well as definitions and methods
used differed between studies. A systematic review of published
data from 43 studies in Nigeria found that the prevalence of
hypertension ranged between 8 and 46.4% depending on the
study population and definitions used.
16
A number of recent large surveys in sub-Saharan Africa
reported the prevalence of hypertension to range from 19 to
50.1%,
6,12,27-34
and a recent systematic review of surveys from
the region confirms the wide variation in prevalence estimates.
5
Prevalence of hypertension reported from different studies
in Africa shows that Nigeria has a high prevalence rate for
hypertension (Table 6). Some of the variation can be explained
by methodological differences (e.g. some have focused on only
rural populations) but variation in the age groups studied is likely
to be a major factor.
A limitation of our study was the non-availability of data
on the use of anti-hypertensive medication in the present study.
However, studies in Nigeria and other sub-Saharan African
countries report that use of hypertensive medication was very
low,
5,13,23,27,32
and so this is unlikely to have significantly impacted
on our prevalence estimate or the findings of association in the
present study. If there was any bias, our estimate would be an
under-estimate.
We observed that women had a higher prevalence of
hypertension than men in Nigeria. This corroborates the findings
of many,
4,5,24,27,35
but not all studies in Africa.
28,32,34
A unique feature of the present study is that it provides
estimates of the prevalence of hypertension among indigenously
resident ethnic groups at a national level. Only one other study
examined the association of ethnicity with hypertension in
Nigeria but it was limited to one region of the country.
15
Some evidence of ethnic variation has been reported in
Kenya where statistically significant differences between ethnic
groups were reported after adjusting for socio-demographic and
TABLE 5.ALL GRADES OF HYPERTENSIONAMONGTHOSE
AGED
≥
40YEARS IN NIGERIA, BY ETHNIC GROUP
Ethnic group
n
Mean age
±
SD (years)
Preva-
lence
(%)
95% CI
Adjust-
ed OR 95% CI
p
-value
Other group 2 024 54.7
±
12.1 41.5 37.5–45.5 1
Kanuri
333 54.4
±
11.7 77.5 71.0–84.0 3.51 2.33–5.29
<
0.001
Nupe
208 53.9
±
10.8 50.5 43.9–57.1 1.85 1.14–3.0 0.01
Tiv
342 55.9
±
13.7 44.4 37.7–51.2 1.65 1.14–2.38 0.01
Igebe
143 54.8
±
12.1 37.8 24.8–50.7 1.64 0.97–2.77 0.06
Fulani
832 54.1
±
11.3 54.6 49.4–59.7 1.47 1.11–1.95 0.01
Ibibio
210 52.6
±
11.5 38.6 30.1–47.0 1.45 0.99–2.13 0.06
Anang
132 54.2
±
11.1 34.1 27.5–40.6 1.45 1.06–1.98 0.02
Hausa
3 361 54.4
±
11.9 52.4 49.5–55.2 1.42 1.14–1.76
<
0.001
Igala
183 55.6
±
12.9 41.5 33.5–49.6 1.38 0.83–2.30 0.22
Edo
218 56.6
±
12.4 39.0 35.8–42.2 1.32 1.01–1.72 0.05
Igbirra
163 56.7
±
13.9 42.3 36.4–48.2 1.22 0.83–1.8 0.30
Ijaw
251 58.3
±
12.9 39.4 28.8–50.1 1.07 0.69–1.67 0.75
Igbo
2 017 57.5
±
12.7 40.4 37.6–43.1 1.04 0.77–1.40 0.78
Ekoi
103 57.3
±
11.0 31.1 27.1–35.0 1.04 0.79–1.36 0.80
Urhobo
266 57.9
±
13.4 36.1 27.1–45.0 0.94 0.58–1.53 0.81
Yoruba
2 525 58.5
±
12.4 39.3 36.4–42.1 0.79 0.63–0.99 0.04
Gbagyi
135 54.8
±
14.3 25.9 18.3–33.6 0.73 0.42–1.26 0.26
*Adjusted for age, gender, place of residence and socio-economic status.
TABLE 6. ESTIMATES OF HYPERTENSION FROM POPULATION-BASED
STUDIES IN SUB-SAHARANAFRICA
Author (year) Place of study
Sample
size
Age
range
(years)
Prevalence
(definition 1)
(%)
Prevalence
(definition 2)
(%)
Present study Nigeria, nationwide 13 504 40+
45.9*
24.3*
Isezuo
et al
.
18
(2011)
Nigeria (rural and
urban)
782 15–65
24.5
Oladapo
et
al
.
19
(2010)
Nigeria (rural)
2 000 18–64
20.8
Adedoyin
et
al
.
20
(2008)
Nigeria (semi-urban) 2 097 20+
36.6*
Omuemu
et
al
.
21
(2007)
Nigeria (rural)
590 15+
20.2*
Olatunbosun
et al
.
29
(2000)
Nigeria, (urban)
998 16–70
10.4
Cooper
et al
.
13
(1997)
Nigeria (rural and
urban)
1 171 25+
14.5*
Andy
et al
.
15
(2012)
Nigeria (rural)
3 869 15+
23.6
Ogah
et al
.
18
(2013)
Nigeria (rural)
2 999 18+
31.8
Ekpenyong
et
al
.
38
(2010)
Nigeria (rural)
2 780 18-60
25
Maher
et al
.
25
(2011)
Uganda (rural)
6 678 All
22.5*
De Ramirez
et
al
.
12
(2010)
Malawi, Rwanda,
Tanzania (rural)
1 485 18+
22
Mathenge
et
al
.
6
(2010)
Kenya (rural and
urban)
4 396 50+
50.1
Damasceno
et
al
.
23
(2009)
Mozambique (rural
and urban)
3 323 25–64
33.1
Tesfaye
et al
.
26
(2009)
Ethiopia (urban)
3 173 25–64
31
Addo
et al
.
27
(2008)
Ghana (urban)
1 015 25+
30.3
Kengne
et al
.
28
(2007)
Cameroon (urban)
2 559 15+
20.8
Steyn
et al
.
24
(2001)
South Africa,
nationwide
13 802 15+
23.9
Van der
Sande
22
(2000)
Gambia
5 369 15+
19
Dewhurst
et
al
.
39
(2011)
Tanzania (rural Hai)
2 223 70+
69.9
Houinato
et
al
.
40
(2008)
Benin
6 853 25–64
27.9
Hendriks
et
al
.
41
(2009–11)
Nigeria, Kenya
(rural), Tanzania,
Namibia (urban)
7 568 18+ Nigeria: 19.3
Kenya: 21.4
Tanzania: 23.7
Namibia: 38
*Medication details not available
Definition 1: Diastolic BP 140 mmHg
≥
or SBP
≥
90 mmHg
Definition 2: Diastolic BP 160 mmHg
≥
or SBP
≥
95 mmHg
