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WATER HARDNESS AND STROKE DEATHS/Comstock et al.
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smoking and strokes. Stroke 5: 483-486, 1974
Winton EF, McCabe LJ: Studies relating to water mineralization and health. J Am Water Works Assoc 62: 26-30, 1970
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three communities of the southeastern United States. In Kessler
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water-hardness in three matched communities in Los Angeles.
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epidemiological study of geographic differences in stroke mortality. II. Results. Stroke 8: 551-557, 1977
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205
hardness of local water supplies. Lancet 1: 827-831, 1968
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between water hardness and death rates in cardiovascular diseases. Acta Med Scand 178: 239-252, 1965
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to the sources and hardness of their water supplies. J Hyg
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36. Crawford MD, Gardner MJ, Morris JN: Changes in water
hardness and local death-rates. Lancet 2: 327-329, 1971
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Incidence of Stroke in an African City: Results from
the Stroke Registry at Ibadan, Nigeria, 1973-1975
B.O.
O S U N T O K U N , O.
BADEMOSI, O.O.
A . B . O . O Y E D I R A N , A N D R.
AKINKUGBE,
CARLISLE
S U M M A R Y Studies based on hospital populations reported from negro communities in several countries in
Africa1 suggest that cerebrovascular disease (CBVD) shows increasing mortality and morbidity in Africans
although 2 decades ago CBVD was believed to be uncommon. We report the first study in the African to determine the incidence of stroke in an urban area, Ibadan, Nigeria.
Stroke Vol 10, No 2, 1979
A STROKE REGISTER (which included subarachnoid hemorrhage (SAH) infracerebral
hemorrhage (CH), cerebral infarction (CI), but excluded transient ischemic attacks, (TIA) and subdural
hematoma) was operated for Ibadan, Nigeria, from
April 1, 1973 to March 30, 1975 as part of the international multicentric program of the Cardiovascular
Diseases Unit of the World Health Organization. Its
purpose was to study the incidence of stroke in several
communities. Total coverage of Ibadan was obtained
by notification to hospitals, general practitioners,
private nursing homes, coroner's office (for cases of
sudden death), and the office of the Medical Officer of
Health for the city. Case finding of stroke patients was
carried out by a Nursing Sister who visited various
health institutions in Ibadan at least once a week. The
register included only those resident for at least one
year in Ibadan. Neurological and clinical evaluation,
where possible, was done by 2 neurologists (B.O.O.
From the Department of Medicine and Department of Preventive
and Social Medicine (Dr. Oyediran), University College Hospital,
Ibadan, Nigeria.
and O.B.) In others, the diagnosis was based on the
case histories and results of available investigations.
Follow up after discharge from the hospitals was
difficult, for in addition to shortage of personnel, incorrect addresses given by patients made tracing an
uphill task and many patients did not return to the
clinics for evaluation. The population data for Ibadan,
provided by the Ministry of Economic Planning,
Western State of Nigeria, were based on projection of
the 1963 census.
Results
During the 2 year period, 318 patients were
registered and this number almost certainly
represented the minimum for most of the patients
were seen in hospitals and nursing homes.
Table 1 shows that the male to female ratio is 5 to 2
compared with a male to female ratio of 1.3 to 1 in the
population. The peak age-specific incidence in the
male is in the eighth decade and in the female in the
7th decade, with higher incidence rates in males than
in females in almost all age groups and generally low
incidence rates in those below the age of 40 years. The
apparently low incidence rates in 8th and 9th decades
STROKE
206
VOL 10, No
2, MARCH-APRIL
1979
TABLE 1 Stroke Registry in Ibadan 1973-75 Incidence Rates
FemaU58
Males
Age in yrs
No. of
patients
Incidence
per 1,000
No. of
patients
Incidence
per 1,000
Total
incidence
0-9
10-19
20-29
30-39
40-49
50-59
60-69
70-79
80
0
4
5
18
54
55
60
28
5
0.03
0.01
0.12
0.9
2.5
5.4
7.8
2.0
0
1
3
8
16
25
27
4
5
0.01
0.01
0.08
0.4
1.4
2.9
1.3
2.1
0.02
0.01
0.11
0.67
2.02
4.4
4.6
2.1
229
0.25
89
0.13
0.26
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in the females and in the 9th decades in the males may
be artifactual due to the low average life expectation
(about 45 years). Those in the 8th and 9th decades in
Ibadan represent only 0.7 percent of the population,
whereas 88% of the male and 85% of the female are
under the age of 40.
Table 2 shows the type-diagnoses of stroke. Two
hundred and sixteen of the patients were judged to be
hypertensive (sustained blood pressure > 160/100 mm
Hg for at least one week after stroke or found to have
other evidence of hypertensive disease — in heart,
kidneys, retina.) Eighty percent of patients with SAH
and CH, 58% of those with non-embolic cerebral infarction and 76% of those with acute but ill-defined
CBVD were hypertensive. Only 67 of the 216
hypertensive patients knew they were hypertensive
prior to the onset of stroke and 57 of them were on
specific treatment for hypertension.
Seventeen patients (5.3%) suffered from diabetes
mellitus.
Table 3 shows the mortality in the series within 3
weeks of admission. Autopsy rate in these patients
was only 17%.
None of the 207 survivors at 3 weeks had a
recurrence of stroke. At 3 months after the ictus only
76 of the patients could be traced, and 3 of these with
an initial diagnoses of CI had suffered a recurrence.
Of the 36 patients who could be traced after a year or
more, none had suffered a recurrence: 27 were on
antihypertensive treatment.
TABLE 2 Ibidan Stroke Registry Diagnoses
No.
Subarachnoid hemorrhage
Cerebral hemorrhage
Cerebral infarction
(i) non-embolic occlusion of
precerebral arteries
(ii) intracranial cerebral
arterial thrombosis
(iii) cerebral embolism
Acute but ill-defined
cerebrovascular disease
36
50
—
Discussion
Results of this study show that stroke in the
Nigerian Africans is commoner in males, its incidence
rises with age, and the major predisposing factors are
hypertension and diabetes mellitus. In contrast to
previously held opinion, based on hospital data,2'3
stroke is not unusually frequent in young Nigerians.
The fall in the incidence rates in males in the 9th
decade and in females in the 8th and 9th decades is
probably due to under-reporting. The higher incidence
rate of stroke in Nigerian males, compared with
females, may be due to Nigerian females' better toleration of hypertension. Acheson (I960)4 showed that
in Ireland there was a strong correlation in males
between coronary artery disease and hypertension and
between hypertension and cerebrovascular disease; in
females there was no such association.
Attempts to obtain the natural history of stroke in
Nigerians were blocked by insurmountable difficulties
which prevented adequate follow up. The mortality at
3 weeks found in this study confirms that in Nigerians
the better prognosis of non-embolic CI compared with
other types and the mortality rates are similar to those
reported in other Africans.1 In the University College
Hospital in Ibadan, tetanus, meningitis and CBVD
are the major diseases of the nervous system causing
death. The annual mortality rate from CBVD, unlike
meningitis, analyzed for the period 1960-1973,
showed a continuous rise in Ibadan.5 The frequency of
CBVD as a cause of death in University College
Hospital, Ibadan, is 4.5%: the other major causes of
deaths in the medical wards of the hospital are liver
%
of total
11.3
15.7
2
0.6
145
8
45.7
2.5
77
24.2
318
100.0
TABLE 3 Mortality of Stroke Within 3 Weeks of Registration
Diagnosis
Subarachnoid hemorrhage
Cerebral hemorrhage
Cerebral infarction
(i) intracerebral arterial
thrombosis
(ii) cerebral embolism
Acute but ill-defined CVA
Total
No.
of deaths
%
of total
22
31
61.1
62.0
38
6
14
26.2
75.0
18.2
111
34.9%
STROKE INCIDENCE IN AN AFRICAN CITY / Osuntokun et al.
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diseases (12%) tetanus (9%) hypertensive heart disease
(8%) renal failure (6%) and meningitis (4%).
An association between high blood pressure and an
increased incidence of cerebrovascular disease has
been established for both CH and CI. 8 9 Reduction in
blood pressure of hypertensive patients by medical
treatment lowers the incidence of future strokes or
recurrence of strokes.10 Of the 27 patients in this community study who suffered from stroke and have been
treated with antihypertensive drugs for more than one
year, none has suffered a recurrence.
Stroke in hypertensives is frequently due to disease
of small intracerebral vessels rather than to
atheroma. 11 ' 12 Hypertension is the major predisposing
factor to stroke in the Nigerians as found in this study
and by others. 2 ' 3 In view of the several studies 1315 that
have indicated that hypertension (and not cerebral
atherosclerosis or elevated serum lipids) is the major
predisposing cause of CBVD in the African negroes,
in whom coronary artery disease is very uncommon,
early detection and treatment of hypertension should
be beneficial. This may help prevent the rising mortality and morbidity of stroke in some African communities.
Acknowledgment
The stroke registry at Ibadan was supported by grants from the
World Health Organization, Geneva, and the Senate of the University of Ibadan, Nigeria.
References
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Incidence of stroke in an African City: results from the Stroke Registry at Ibadan, Nigeria,
1973-1975.
B O Osuntokun, O Bademosi, O O Akinkugbe, A B Oyediran and R Carlisle
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Stroke. 1979;10:205-207
doi: 10.1161/01.STR.10.2.205
Stroke is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
Copyright © 1979 American Heart Association, Inc. All rights reserved.
Print ISSN: 0039-2499. Online ISSN: 1524-4628
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