CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 7, August 2012
382
AFRICA
CVD of 10.8% among a nationally representative sample of the
adult population of hypertensive Nigerians. Most studies of this
nature have been conducted in hypertensive Nigerian patients
attending healthcare facilities.
The relatively high prevalence of TOD among the community
of rural-dwelling adults is worrisome as it approaches previously
reported hospital-based values of 53.3%
13
and 60.1%.
12
Blacks
have been shown to have more severe forms of hypertension
with greater risk of TOD.
25,26
This may be due to the fact that
85.8% of the subjects were newly diagnosed hypertensives.
Some of the subjects had had their blood pressure measured
for the first time during the study. Of those who had had previous
blood pressure measurements, the definition of hypertension
by their attending medical team was 160/95 mmHg. These
physicians had failed to commence appropriate management
even at this level. Furthermore, only 18.6% of the self-reported
hypertensives were on any form of treatment, which was mostly
suboptimal. Of these, only 27.3% had their blood pressure
controlled. There is an urgent need for training and retraining of
both the care givers and care seekers at the community and PHC
levels in order to reduce the burden of CVD in the population.
The prevalence of ECG-LVH was nearly 28%, based on
Araoye’s criteria,
18
indicating that these individuals had more
severe LVH with a possibly worse prognosis. This may have
been due to a long duration of undiagnosed hypertension in the
subjects. LVH has been associated with increased incidence of
CHF, coronary artery disease, stroke, arrhythmias and sudden
death.
27
In those receiving treatment for hypertension, the
antihypertensives being used were inadequate to regress their
LVH. LVH places the subjects at risk of developing adverse
cardiovascular events. The percentage of subjects with LVH was
lower than the 31.0%
12
and 43.3%
13
obtained in previous studies,
although these were hospital based in urban settings. Another
study in hypertensive urban civil servants in Ghana found a
prevalence of 33.3%.
28
Left atrial enlargement (LAE) was present on the ECGs of
21.9% of the subjects and atrial fibrillation in 16.4%. These
are known risk factors for thrombo-embolic strokes and in
the presence of hypertension, they may worsen the prognosis.
Hypertension, a major risk factor for stroke in sub-Saharan
Africa, including Nigeria, has been reported to occur in 33 to
62% of those with cerebral infarction and 60 to 92% of those
with cerebral haemorrhage.
29
The relatively high prevalence of stroke in our study
population was 6.3% and this was comparable to a hospital-
based report of 8.9%
12
but much higher than the 0.8% reported in
a similar setting.
13
In sub-Saharan Africa, stroke is a major CVD
of public health concern, with high morbidity and mortality,
affecting people in the prime of their lives.
30,31
It also imposes
a high economic burden on the healthcare systems, which this
low-income country cannot afford.
Kidney damage was found in 27.5% of the subjects and of
these, 12.3% had microalbuminuria, while 15.2% had gross
proteinuria. There is disparity between our findings and a
previous study that reported microalbuminuria in 37% and overt
proteinuria in 2% of newly diagnosed Nigerian hypertensives.
32
Microalbuminuria is a sensitive marker for renal damage in
hypertension.
16
In our study, subjects who had ECG abnormalities and
evidence of kidney damage had statistically significantly (
p
<
0.001) higher SBP and DBP compared with subjects who had
neither TOD. In a study on TOD in hypertensive Ghanaian
civil servants,
28
trace proteins were found in 8.8%, proteinuria
in 13.4% and chronic kidney disease in 4% of the participants.
The high rate of proteinuria in our study population was a
cause of concern as efforts in the primary prevention of chronic
kidney disease should be intensified in this low-resource setting.
Failure to do so will increase the economic burden on the fragile
healthcare system.
Based on the fact that grades 3 and 4 hypertensive retinopathy
are used as evidence for TOD,
31
the prevalence of hypertensive
retinopathy in our study was 2.2% and was comparable to
the prevalence reported in studies in sub-Saharan Africa.
28,32,33
These studies reported a rarity of hypertensive retinopathy in
this region, unlike the high prevalence in economically more
advanced nations.
34
About 78% of our subjects had either grade
1 or grade 2 retinopathy.
Of the participants in this study, 10.8% had established
CVD. Of these, 6.3% had stroke, 4.6% had CHF, 3.6% had
peripheral vascular disease and 1.7% had ischaemic heart
disease. Hypertension plays a significant role in the causation
of CHF in Nigeria.
12
Heart failure is another complication
which would impose a social and economic burden on the
populace. This underscores the importance of establishing
intervention programmes for primary prevention, early detection
and appropriate management of hypertension in this rural
population. Although the prevalence of ischaemic heart disease
was low in this study, its presence in the population may be
significant, with epidemiological transition occurring at a rate
faster than previously thought.
The odds of developing TOD were highest in participants
with blood pressure
≥
180/110 mmHg, followed by newly
diagnosed hypertensives and those with diabetes. Previous
studies have shown a more positive correlation of hypertensive
TOD with SBP than with DBP.
12,35
Since hypertension is a
silent disease, there is a need to create awareness to encourage
opportunistic screening. Patients should be encouraged to adopt
healthy lifestyles for the primary prevention of CVD as they
TABLE 5. ASSOCIATION BETWEEN HYPERTENSIVE
TARGET-ORGAN DAMAGEAND SELECTEDVARIABLES
Detection of hypertension
OR* (95% CI) for
target-organ damage
Self-reported
1.00
Newly diagnosed
3.61 (0.59–8.73)
BMI
≤
24.9 kg/m
2
1.00
25.0–29.9 kg/m
2
0.95 (0.28–3.26)
≥
30.0 kg/m
2
1.44 (0.45–5.74)
Hypertension classification
BP
<
140/90 mmHg
1.00
SBP 140–159 mmHg/DBP 90–99 mmHg
1.34 (0.23–2.95)
SBP 160–179 mmHg/DBP 100–109 mmHg
1.29 (0.20–4.95)
SBP
>
180 mmHg/DBP
>
110 mmHg
4.76 (1.30–13.06)
Diabetes mellitus
No diabetes
1.00
Diabetes
1.85 (0.74–8.59)
*OR (odds ratio) adjusted for age, gender, smoking, level of education,
blood pressure control. BMI
=
body mass index.
