Results

The total study population comprised 70 955 males and 77 180 females, with 39 458 and 45 694 respectively aged 15 and over. Two people, in whom the history from the relatives suggested a stroke, had moved from the area between the time of the census and the time of the study, and three had died. Five people gave a history suggestive of stroke but on examination had made a full recovery. Four people were identified subsequent to the census but before the date for point prevalence of impairment and disability and were therefore included. No one under the age of 15 was identified as having had a stroke.

Other causes of hemiplegia identified in persons over the age of 10 were febrile illness in childhood (28) including meningitis and measles, cerebral malaria (10), cerebral palsy (27), head injury (seven), polio with upper and lower limb involvement (two), likely cranial space occupying lesion (two), hydrocephalus (three) (all with bilateral signs), and near drowning in one giving a total of 80 cases.

A total of 108 people were identified as fitting the criteria for the study. In only 14 of those included in the study were actual hospital records identified although more names were identified from ward admission books. Of the new people identified from hospital records five, when subsequently reviewed, had made a complete recovery and the remainder had died after discharge. Only 13 gave a history of having had any contact with physiotherapy services since their discharge from hospital and only five of these were identified from physiotherapy records. No new persons were identified from the health centres or physiotherapy records.

There were 61 men and 47 women. The median age for both sexes was 70 years (range 18–100). Median age at the time of first stroke was 65 years (range 15–100) (men 66 years; women 65 years). Thirty (49%) men were 65 years and older compared with 33 (70%) women, and 11 of the 15 over 85 were men. Age specific rates of prevalence are shown in table1. Table 2 shows age specific rates for those requiring help in at least one activity of daily living.

The calculated prevalence/100 000 for the whole population (148 135) was 73, whereas for those aged 15 and over (85 152) it was 127 (155 for men and 103 for women). The prevalence for those aged 55 and over was 566, with 623 for men and 510 for women. The rate for those aged 65 and over was 876, with 975 for men and 786 for women.

All but two had been born and brought up in Hai district and all had spent their adult life living there except for three who had travelled with their work at times.

There was no history of hypertension in 69 patients, of whom 61 had never had their blood pressure measured. Of the 25 taking antihypertensive drugs at the time of their stroke four had been on treatment for less than 1 year; 11 further patients had defaulted from treatment, five within the year before stroke. Three patients had been diagnosed to be hypertensive at some stage but had never received treatment. Of the 40 who had had their blood pressure measured in the year before their stroke only 14 (35%) had had this measured more often than every 3 months.

After the stroke 56 (52%) received treatment for high blood pressure at some time. However, after discharge from hospital (or after the stroke in those not admitted) 44 (41%) had never had their blood pressure measured whereas seven (6%) had only had it measured once. Of the remainder only 20 (19%) had had their blood pressure measured at least monthly.

Seven had had a previous stroke and one a transient ischaemic attack. Two gave a history of angina and one a history of claudication. Type II diabetes mellitus was present in three. Two were pregnant at the time of their stroke. Sixteen were current smokers and 11 ex-smokers. Only one was taking aspirin regularly before the stroke and only one after the stroke.

All of the patients were fully independent with maximum Barthel scores before their first stroke. Territory of stroke was right carotid in 67, left carotid in 40, and bilateral in one. No patients with involvement of the posterior circulation were identified but these patients are much more difficult to identify on screening.

At the time of examination 80 (74%) had no dysarthria, 15 slight slurring, six (6%) were difficult to understand, four were incomprehensible, and three were aphasic. Only one had impaired swallowing. Visual fields were normal in 76 (70%), with homonymous hemianopia or visual inattention in 20 (19%) whereas it was impossible to assess the remaining 12. Twenty three (21%) were bedbound, 12 (11%) chairbound, 12 (11%) housebound, 53 (49%) had limited mobility, and eight were independently mobile.

The figure shows the percentages of men and women dependent for activities of daily living as assessed by the Barthel score. Median Barthel score was 17 and 37 had a Barthel total of <10.

Forty one (40%) were independent for washing, dressing, bathing, feeding, transferring, or toileting, the criteria used to define “assistance in at least one self care activity” in the Auckland study.3 Median age for this group was 67 years (range 18–92 years) whereas median age at first stroke for this group was 58 years (range 15–90 years). This independent group included 31 (51%) of the men and only 10 (21%)of the women.

Discussion

This type of study is difficult to perform in rural Africa. A conventional prevalence study would include persons who had ever had a stroke and had recovered. However, in this population where contact with western style health services is infrequent, ascertainment for those with a history of stroke who had made a complete recovery would be unreliable without a longer and more complicated screening questionnaire. Verification would also be much more difficult and unreliable than in those patients in whom there was a residual deficit. In fact only eight patients were identified as having had a stroke from which they had made a complete recovery.

Although we can be relatively sure about the diagnosis in the cases that we did see with residual disability or impairment the numbers may be a slight underestimate of the true levels.

Our estimates of age are as accurate as possible in such a population where birth certificates are almost non-existent. With the methods used to estimate age a phenomenon of “age heaping” tends to occur where ages have a tendency to be rounded up or down by people to the nearest 5 years. When our results were compared with the age of the people as recorded in the yearly census data (for which the same methods are used) they showed good agreement.

We were not able to perform a validation study in this population of the questions used and cannot, therefore, quote rates for sensitivity and specificity of the questions. A recent United Kingdom study to validate a postal questionnaire for assessing the prevalence of stroke15 found that the question “have you ever had a stroke?” had a sensitivity of 95% and a specificity of 96%. Although it is hard to extrapolate from a postal questionnaire in a United Kingdom population to a house to house survey in a rural Tanzanian population it is likely that the question “is there anyone in the household with a history of stroke?” would have a high sensitivity although the specificity is likely to be considerably less. It is worth noting that kiharusi, the Swahili word for stroke, is also used by some people for other disorders associated with the brain, such as Parkinson's disease. The questions were asked in the appropriate local languages and the enumerators had been educated at workshops about the type of patients they were looking for. Further patients with residual impairment or disability relating to stroke were not found by the additional secondary measures which was reassuring with respect to the efficiency of the case ascertainment by the enumerators and suggests that the sensitivity of the methods was high. Feedback about the results was provided to the staff of the project at the end of the study and the enumerators have asked about prevalent stroke cases in the 4 yearly censuses since then. Further cases have been identified but none of these was living in the area with a prevalent impairment or disability from stroke at the time of the study.

Ideally we would have liked to have examined a sample of the “negative” questionnaire patients to be sure they did not have stroke related disability but, as the “stroke rate” is low, this sample would have to be very large and was not feasible.

Undoubtedly non-hemiplegic strokes with, for example, disability limited to speech or visual problems, and posterior circulation strokes with, for example, symptoms restricted to balance problems, will have been missed as specific questions to identify these problems were not used. Cognitive impairment was also not assessed. However, overall, it is likely that few of the disabled patients with strokes who were left with limb weakness were missed, and it is known from studies in developed countries that most patients disabled from stroke do have residual limb weakness. To ensure full and accurate completion of the questionnaire question 3 was deliberately kept simple and did not include all the activities of daily living as assessed by the Barthel index. However, we think that in conjunction with the other questions most people disabled by stroke will have been picked up.

As each case was seen and examined by one of us to confirm or refute the diagnosis of stroke this excluded interobserver errors in the making of the diagnosis. We are therefore confident that false positive patients are unlikely, although bearing in mind that brain CT was not available. If hemiplegia is due to malignancy then without treatment the neurological deficit is usually progressive and subsequently fatal. Infectious causes are more numerous in this region compared with developed countries and include such diagnoses as tuberculoma, gumma, echinococcus cysts, and AIDS. With these conditions there are likely to be other signs and symptoms and without treatment the disease is likely to be progressive.

As expected, the main impact of stroke is in the older age groups although, with the few stroke patients in this study, the confidence intervals are wide.

One explanation of the lower prevalence is likely to be increased case fatality for strokes in a country where medical and rehabilitation services are limited. Only 13 patients had had any regular physiotherapy. No data are, however, available for case fatality for stroke in this area.

A recent paper3 described the prevalence of stroke and stroke related disability in Auckland, New Zealand from two population based studies, one in 1981 with follow up of patients to 14 years, and the second in 1991–2 with 3 years of follow up. Using an actuarial model, they looked at overall stroke prevalence by age and sex and also prevalence for incomplete recovery and those needing help in at least one self care activity (washing, dressing, bathing, feeding, transferring, or toileting). Results for the three groups age standardised to the Segi World Population 15 years and over were respectively for men 991, 493, and 156; for women 706, 448, and 188; and for the group as a whole 833, 461, and 173. Thus, the rates for those needing help in activities of daily living were a little higher than those found in this study (tables 1, 2).

From the Auckland study 20% of stroke survivors required assistance with at least one activity, most (60%) of whom required institutional care. Institutional care is not available in this area but there is a great respect for elders and an acceptance that disabled people should be looked after by their families. Some severely disabled patients had survived.

There are few data on stroke in the community in sub-Saharan Africa. In a study from central Ethiopia,16 between 1986 and 1988, a door to door survey was conducted on a stable rural population of 60 820. Thirty eight patients were found to have hemiparesis but in only nine was this thought to be secondary to cerebrovascular accident (15 cases/100 000).

A research protocol for measuring the prevalence of neurological disorders in developing countries was established in a pilot study of 903 patients in a rural community in Nigeria.17 This incorporated a screening questionnaire and simple neurological examination by “non-doctor health care workers” with subsequent examination by a neurologist of patients positively identified as having a potential neurological illness. Using this, 18 594 patients were screened in a small town of 20 000,18 and 11 patients with disabilities relating to stroke were identified, giving a crude point prevalence ratio for stroke of 58/100 000. It should be noted that two of these patients were under the age of 10 and the “stroke” was thought to be secondary to sickle cell disease.

There are even fewer data on the natural history of stroke in sub-Saharan Africa. A study from Pretoria, South Africa,19which included brain CT, followed up 116 consecutive patients with stroke admitted to hospital and reported a 33.6% 1 month case fatality rate (22.4% for those with cerebral infarction and 58% for those with cerebral haemorrhage). This reflects a patient group admitted to hospital and the proportion of those patients with a stroke admitted to hospital in sub-Saharan Africa is likely to be lower than in developed countries.

In developed countries, studies looking at outcome have largely assessed cohorts of patients with incident stroke longitudinally, at set intervals (usually 6 or 12 months) after the acute event. In the Frenchay Stroke Project 976 community stroke patients were assessed at 6 months and 53% were partially or totally dependent for activities of daily living.2 In the Oxfordshire Community Stroke Project 45% of stroke victims were independent at 1 year.20

Most other studies have only followed up patients discharged from hospital after an acute stroke.21 22 Even in developed countries up to one third of patients with stroke are never admitted to hospital and therefore these figures will underestimate the disability in the population.23 There has been a wide variation in reported levels of disability in stroke survivors which is explained partly by the use of many different outcome measures and also the varying times of assessment after stroke.

Increasing age is the strongest risk factor for cerebral infarction, primary intracranial haemorrhage, and subarachnoid haemorrhage.24 In studies from developed countries there is a small increased risk of stroke in men,25 most prominent in middle age and disappearing in the very elderly people, and absent in the young. However, as more women survive to old age, more women have strokes.

Previous studies relating to stroke in sub-Saharan Africa have shown that, in those admitted to hospital, males outnumber females by 2:1 and it has been suggested that this is because women are less likely to go to hospital rather than a true reflection of a major difference in incidence.26

In addition to showing that the younger patients with strokes were more likely to have had a good outcome, our data show that the women were generally more disabled and dependent than the men. This, unlike in developed countries, cannot be explained by increased numbers of women in the older age bands of the population as the proportions were relatively equal. The apparent relative survival advantage in males in the population as a whole may be due in part to high maternal mortality rates, although despite this, in the maternal age range all cause mortality rates are higher for men than women.13 The main reason is likely to be the lack of ischaemic heart disease which causes higher mortality in developed countries and is more likely to affect men than women, particularly in the younger age groups.

In developed countries ischaemic heart disease is common among stroke patients and in those who initially survive their stroke it is responsible for half of all deaths at follow up.27However, ischaemic heart disease is rare in rural Africa as are other markers of atheroma.28 Our population has previously been shown to have a low prevalence of risk factors for coronary heart disease,29 and previous surveys in the area have shown that patients giving a history of angina or myocardial infarction are virtually non-existent. Without a high prevalence of other risk factors high blood pressure remains the main identifiable risk factor (apart from age) in this population.

Data from studies looking at prevalence of hypertension in sub-Saharan Africa show a wide variation30 with generally a higher prevalence of hypertension in urban than rural populations of the same ethnic origin. Previous data from surveys within the AMMP areas have shown rates of hypertension of 10.9% in Hai.29

An increase in blood pressure, both diastolic and systolic, within a healthy population is strongly associated with subsequent stroke risk31 whereas treatment of hypertension reduces stroke risk.32 Treatment of blood pressure is therefore the main risk factor modification applicable in this population as a whole, and in individual patients. However, the costs of antihypertensive treatment, which include case finding and monitoring, in addition to the cost of the treatment itself are often prohibitive in developing countries. This is the main reason for the high antihypertensive treatment default rates found in previous African stroke studies.28

Even if efforts to treat hypertension to prevent strokes in sub-Saharan Africa are successful, the demographic transition will inevitably bring with it a major increase in the incidence of stroke, and along with this the prevalence of disability relating to stroke. At present these patients are looked after at home by their relatives, and while numbers are small this will continue, but increasing numbers of dependent elderly people are likely to be a major burden on this care structure.