CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 9/10, October/November 2013
346
AFRICA
Declaration of Helsinki. Written informed consent was obtained
from participants after an explanation of the nature of the study.
Statistical analysis
A customised database was created in Microsoft Access and two
trained data-entry clerks entered the data. Data entered by one
operator were checked by the second operator and corrections
were made when necessary. Quality assurance procedures included
a random verification of filled forms completed in the field and
at the project office. The data were cleaned and analysed using
a statistical package (Stata 11; StataCorp, College Station, TX).
Prevalence estimates together with 95% confidence intervals
(CI) for hypertension are presented. Multiple logistic regression
analysis was performed to identify risk factors for hypertension
and to estimate adjusted odds ratios (OR). All the analyses
accounted for clustering (design effect) due to the cluster
sampling design adopted for the study. Missing values were
excluded from all the analyses;
p
-values
<
0.05 were considered
statistically significant.
Results
A total of 13 591 people took part in the study, 13 504 (99.4%)
of whom had a valid blood pressure measurement. The mean
age of participants was 55.9 years (
±
12.4) (men: 56.8; women:
55.2 years). The mean age of respondents in the south-east
geo-political zone was the highest (58.6
±
12.8 years) and it was
the lowest in the north-east zone (53.8
±
11.6 years). The mean
age in the north-west was 54.2 years (
±
11.8), in north-central
it was 55.8 years (
±
12.7), in south-south it was 56 years (
±
12.2) and in south-west, 57.8 years (
±
11.8). Over 60% of those
surveyed were under the age of 60 years.
There were more females in the sample (54.1%) than males,
and rural respondents constituted 77.6% of the sample (Table
1). Over 50% of the study population belonged to the four most
populous ethnic groups in Nigeria: Hausa, Igbo, Yoruba and
Fulani.
The overall prevalence of hypertension was 44.9% (95%
CI: 43.5–46.3%). The prevalence of grade 3 hypertension (the
TABLE 1. DEMOGRAPHIC CHARACTERISTICSAND MEAN BLOOD
PRESSURE OF THE STUDY POPULATION
Parameters
Frequency
(n)
Percent
(%)
Mean systolic
BP (mmHg) (SD)
Mean diastolic
BP (mm Hg) (SD)
surveyed
13 504
138.2 (25.9)
83.9 (15.3)
Age groups (years)
40–49
4 858 36.0
130.2 (21.8)
81.9 (14.2)
50–59
3 554 26.3
139.3 (26.0)
85.1 (15.4)
60–69
2 758 20.4
144.0 (27.0)
85.2 (15.8)
70–79
1 643 12.2
146 (27.6)
84.4 (16.3)
≥
80
691
5.1
146.3 (28.6)
84.4 (16.6)
Gender
Male
6 203 45.9
136.8 (24.6)
83.4 (15.0)
Female
7 301 54.1
139.3 (27.0)
84.2 (15.6)
Residence
Rural
10 478 77.6
137.2 (25.5)
83.1 (15.0)
Urban
3 026 22.4
141.6 (27.1)
86.6 (16.1)
Literacy
Literate
5 891 43.6
136.4 (25.1)
83.7 (15.3)
Illiterate
7 613 56.4
139.5 (26.5)
84.0 (15.3)
Geo-political zone
North-east
1 707 12.6
144.4 (27.7)
90.4 (16.5)
South-east
1 657 12.3
138.4 (28.0)
79.0 (14.8)
South-south
1 845 13.7
133.1 (25.9)
77.9 (14.8)
North-west
3 577 26.5
140.3 (24.3)
87.5 (13.7)
South-west
2 708 20.1
137.1 (26.4)
81.9 (15.0)
North-central
2 010 14.9
135.0 (23.4)
83.9 (14.5)
Socio-economic status
Most affluent
4 383 32.5
135.2 (24.5)
82.5 (14.7)
Moderately affluent
4 676 34.6
137.2 (25.4)
82.9 (14.9)
Least affluent
4 445 32.9
142.1 (27.4)
86.3 (16.1)
Body mass index
Underweight
1 495 11.1
134.3 (25.9)
81.2 (15.8)
Normal
8 156 60.4
136.1 (25.1)
82.7 (14.9)
Overweight
2 588 19.2
142.3 (26.1)
86.4 (15.2)
Obese
1 113
8.2
147.9 (27.5)
89.8 (15.4)
Missing data
152
1.1
TABLE 2. PREVALENCE OF HYPERTENSIONANDASSOCIATION
WITH SOCIO-DEMOGRAPHIC FACTORS
Parameters (n)
Any
hypertension
SBP
≥
140,
DBP
≥
90 mmHg
Hypertension
grade 2 and 3
SBP
≥
160,
DBP
≥
100 mmHg
Hypertension
grade 3
SBP
≥
180,
DBP
≥
110 mmHg
% 95% CI
% 95% CI
% 95% CI
All ages (13 504)
44.7 43.5–46.3 22.0 20.9–23.2 9.9 9.2–10.6
Age group (years)
40–49 (4 858)
32.1 30.2–33.9 12.8 11.6–14.1 5.4 4.6–6.2
50–59 (3 554)
47.1 44.9–49.2 23.4 21.5–25.2 10.3 9.1-11.4
60–69 (2 758)
54.2 52.1–56.3 28.4 26.6–30.3 12.8 11.5–14.1
70–79 (1 643)
57.1 54.2–59.9 31.2 28.7–33.6 14.9 13.0–16.8
≥
80 (691)
58.2 54.4–61.9 32.9 29.4–36.3 15.9 13.1–18.7
p
<
0.0001
p
<
0.0001
p
<
0.0001
Gender
Male (6 203)
42.6 40.9–44.4 19.2 17.8–20.5 8.5 7.7–9.3
Female (7 301)
46.8 45.3–48.4 24.5 23.1–25.9 11.1 10.1–12.0
p
<
0.0001
p
<
0.0001
p
<
0.0001
Residence
Rural
43.0 41.3–44.6 20.5 19.2–21.8 9.1 8.3–9.8
Urban
51.6 48.4–54.9 27.3 24.5–30.2 12.8 10.9–14.8
p
<
0.0001
p
<
0.0001
p
<
0.0002
Literacy
Literate (5 891)
42.0 40.0–43.9 19.9 18.4–22.2 8.9 7.9–9.8
Illiterate (7 613)
47.2 45.5–48.9 23.6 22.2–25.1 10.7 9.8–11.6
p
<
0.0001
p
<
0.0001
p
<
0.001
Geopolitical zone
North-east (1 707)
60.5 55.1–65.8 33.5 28.7–38.2 16.5 13.1–20.0
South-east (1 657)
41.0 38.0–44.0 20.7 18.4–23.0 9.9 8.3–11.5
South-south (1 845)
34.2 31.2–37.2 17.0 14.6–19.4 7.0 5.4–8.7
North-west (3 577)
51.5 48.7–54.2 24.2 21.6–26.8 10.1 8.5–11.6
South-west (2 708)
40.1 37.1–43.2 19.7 17.4–22.0 9.2 7.9–10.5
North-central (2 010)
39.5 35.7–43.3 17.4 14.8–19.9 7.6 6.2–8.9
p
<
0.0001
p
<
0.0001
p
<
0.0001
Socio-economic status
Affluent (4 383)
39.2 37.4–41.0 18.0 16.7–19.3 7.7 6.8–8.6
Moderately affluent (4 676) 43.5 41.4–45.5 20.0 18.5–21.6 8.8 7.8–9.8
Least affluent (4 445)
52.1 49.9–54.2 28.1 26.1–30.1 13.3 11.8–14.7
p
<
0.0001
p
<
0.0001
p
<
0.0001
Body mass index (13 352)
Underweight (1 495)
39.6 36.6–42.6 18.7 16.5–21.0 8.5 6.9–10.1
Normal (8 156)
41.7 40.1–43.2 19.5 18.3–20.7 8.5 7.7–9.3
Overweight (2 588)
50.9 48.7–53.2 26.0 24.0–28.0 11.9 10.5–13.3
Obese (1 113)
59.8 56.3–63.2 34.2 31.1–37.4 16.2 13.9–18.4
p
<
0.0001
p
<
0.0001
p
<
0.0001
