Incidence of Epilepsy in Rural Central Ethiopia

Transcription

1 ~ ~~ ~~ Epilepsia, 38(5): , 1997 Lippincott-Raven Publishers, Philadelphia 0 International League Against Epilepsy Incidence of Epilepsy in Rural Central Ethiopia Redda Tekle-Haimanot, *Lars Forsgren, and *Jan Ekstedt Department of Medicine, Addis Abnba University, Ethiopia; and *Department of Neurology, Umed University Hospital, UmeB, Sweden ~ ~ ~ Summary: Purpose: To study the incidence of epilepsy in a rural area of Ethiopia. Methods: A community-based study was performed in a random sample of villages with 61,686 inhabitants in a rural area of central Ethiopia. In a door-to-door survey, all inhabitants in the study area were interviewed about seizures. A standardized protocol was used. All new cases with epilepsy that had occurred since a previous study was made 3.5 years earlier were included. Fifty-three of the subjects were investigated with EEG. Results: One-hundred thirty-nine incident cases were identified, corresponding to an annual incidence of 64 in 100,000 inhabitants [95% confidence interval (CI) 44-84]. The corresponding rate for males was 72 (CI ); for females, it was 57 (CI 31-84). The highest age-specific incidence occurred in the youngest age groups (0-9 years); the next highest was in the group aged years. Generalized convulsive seizures occurred in 69%, partial seizures occurred in 20%, and unclassifiable seizures occurred in 11%. Seizures occurred daily in 10% and weekly in another 14%; 33% had monthly seizures. Twenty-two percent had a family history of epilepsy. A history of head trauma was ascertained in 5.7% and was the most common possible etiologic factor identified. Thirteen percent were treated with antiepileptic drugs (AEDs). Conclusions: The incidence of epilepsy in Ethiopia is high. A high incidence in combination with a prevalence of epilepsy in the study area comparable to that in the rest of the world may be explained by a high degree of spontaneous remission of epilepsy and/or a high mortality due to epilepsy. Despite health education on epilepsy given to the community, a minority of subjects were treated with AEDs, which may reflect the inadequacies of the health services and transportation difficulties faced by the patients. Key Words: Epidemiology-Incidence-Seizures-Epilepsy- Africa. The limited available prevalence studies from developing countries show variations which may be explained in part on the basis of differences in investigatory methodologies. There are also pockets or foci of populations in which a high prevalence of epilepsy has been reported. These include the Guaymi Indians in Panama with a prevalence of 57 in 1,000 (l), the Pogoro tribe in Tanzania with a prevalence of 20 in 1,000 (21, and inhabitants of Grand Bassa County of Liberia with a prevalence of 28 in 1,000 (3). In a recent review of management of epilepsy in developing countries, Kshirsagar and Shah (4) refer to the claim that epilepsy in developing countries may be twice that in the developed countries. This may be true. However, available community-based epidemiological studies do not appear to confirm the claim, at least in the two general African populations studied. Community-based studies in Nigeria (5) and Accepted December 19, Address correspondence and reprint requests to Professor R. Tekle-Haimanot at P.O. Box 4147, Addis Ababa, Ethiopia. our own survey in Ethiopia (6) have reported prevalences of 5.3 and 5.2, respectively. Almost no studies have been made of the incidence of epilepsy in developing countries. We are aware of only one such study, made in Africa (7). We report the results of a incidence study of epilepsy in a rural Ethiopian population. MATERIALS AND METHODS Study area and population The study was conducted in the rural subdistrict of Meskan and Mareko district in the central Administrative Region of Shoa. The subdistrict is situated 130 km south of Addis Ababa, the national capital. The total population of the subdistrict was 182,000. The population is organized into peasant and urban dwellers associations. There are three towns with six urban dwellers associations and 82 peasant associations (villages) in the subdistrict. Topographically, the subdistrict is divided into highlands in the north and lowlands in the south. The ethnic groups in the surveyed areas were Oromo, Amhara, Kembata, Tigre, and Gurage. The Gurage 541

2 542 R. TEKLE-HAIMANOT ET AL. ethnic group, with the subethnic groups of Meskan, Mareko, Silti, and Sodo, was the predominant one. The main occupation of the inhabitants is plow-cultivation of maize, sorghum, wheat, and Teff (Eragrostis tef). The highlanders cultivate Enset (Ensete ventricosum), a false banana. The core of the underground part of the plants is used to produce the staple diet of kocho. The lowlanders eat mainly bread made from maize flour. The subdistrict is served by a health center, which is run by four general practitioners and is situated in Butajira town (population 15,000), the administrative center of the subdistrict. There are two additional satellite health stations in the subdistrict. The survey With use of a table of random numbers, a 30% random sample of the peasant associations was taken. The survey was conducted in 25 of the 82 peasant associations and in the three towns in the subdistrict. All households in the selected associations were surveyed, resulting in the inclusion of 60,820 inhabitants. In 1983 and 1985, two pilot surveys were conducted in communities near the project area. These pilot studies were used to improve on the logistics of the epidemiological studies as well as on the protocol questionnaires. Secondary-school graduates from the community were recruited and used as lay health-workers (enumerators). Recruitment criteria included sound knowledge of the local customs, culture, and dialects, as well as previous experience in similar field survey. The lay health-workers were then trained by epidemiologists and clinicians on the questionnaires and instructed in simple observations and examinations of persons with neurological problems. Experts from the Ethiopian Mapping Institute instructed them in the basic art of simple mapping of a village. The field workers traveled on foot or horseback in the villages and lived with the villagers, who in many instances provided their meals. They were thus very well accepted by the population. In each village, 2 enumerators with a supervisor mapped and numbered with chalk every house except centers of worship, schools, administrative offices, and other public facilities such as shops and millhouses. The lay health-workers then conducted doorto-door interviews and administered questionnaires to screen persons with neurological disorders. The head of the household or his wife provided information about each member of the family. All those with medical problems and physical and mental disabilities were further scrutinized through another questionnaire to screen those with symptoms and signs of the neurological disorders, including seizures. A special epilepsy form was administered to obtain additional information from persons in the household with episodes of unconsciousness with or without frothing, biting of the tongue, or incontinence of urine and from persons who had sudden jerky movements in part of the body. When possible, EEG recordings were performed on persons with active epilepsy. EEGs were recorded with a Nihon-Kohden Neurofax 7314F machine installed in a building 18m2 constructed from a transport container and situated at the Health Center in Butajira town. The enumerators with the supervisor interviewed the affected subjects and performed simple examinations according to the training they had received from neurologists. Neurologists regularly visited the villages to examine and validate symptoms and diagnosis in all subjects with possible neurological disease. Pretests of the screening instrument showed it to have a sensitivity of 91% and a specificity of 85% for the detection of epilepsy (8). Beginning in May 1990, the population was resurveyed for detection of incident cases with epilepsy. The average observation period (the period since the time of the prevalence investigation) was 3.5 years (range 2-4 years). The observation period of seizure frequency and treatment for individual persons with epilepsy (i.e., the time from initial seizure to identification) ranged from a few months to 4 years. During the investigation period for the incidence study, 3,008 persons died, 6,312 were born, 3,772 moved away, and 2,200 moved into the investigation area. The population at the end of the study was 62,552. The mean population (61,686) during the study was used for calculation of incidence. An epileptic seizure was defined as a sudden and transitory event of motor, sensory, autonomic, or psychic nature, which is assumed to be the result of transient excessive discharge of a hyperexcitable population of neurons in the brain (9). History, examination, and laboratory investigations had to make alternative diagnoses unlikely. An unprovoked seizure was defined as a seizure occurring without an identified proximate precipitant that excluded seizures associated only with an acute insult to the CNS or with generalized systemic metabolic disturbance (acute symptomatic seizures) (10). Proximate was defined to mean occurring within 7 days of an acute event or during an active process (e.g., infection, toxic process, withdrawal) (11). Seizures were classified by type according to established clinical and EEG criteria (12). Epilepsy was defined as a condition characterized by recurrent (at least two) unprovoked seizures. Head trauma refers to trauma with loss of conscious-

3 INCIDENCE OF EPILEPSY IN ETHIOPIA 543 TABLE 1. Age- and sex-specific incidence per 100,000 person-years of initial diagnosis of epilepsy in rural Ethiopia during a mean observation period of 3.5 years Population n Incidence Age (yr) M F Total M F Total M F Total ,241 10,350 20, ,492 7,659 16, ,479 3,754 6, ,960 3,781 6, ,349 2,418 4, ,536 1,494 3, ,216 1,138 2, , Total 30,139 31,547 61, ness or amnesia. Cases with skull fractures and open head injuries after trauma were also included in this group, regardless of the presence of loss of consciousness or amnesia. A family history of epilepsy refers to a history of epilepsy, obtained from the subject, a relative, or both, in any type of relative (first-, second-, or third-degree relative). Statistics The numerator and denominator for incidence calculations are defined herein. Confidence limits (CI) were calculated according to the method of Colton (13). The adjustment by age to the 1986 United States population (14) was made using the direct method. RESULTS One hundred thirty-nine persons with previously undiagnosed epilepsy were identified. This corresponds to an annual incidence of 64 in 100,000 (95% CI 44-84) [for males 72 (CI ); for females 57 (CI 31-84)]. The age-specific incidence was highest in the group aged 0-9 years; the next highest incidence was that in the group aged years; the third highest was in the group aged years (Table 1). Among the 139 persons with epilepsy identified, 49% were below the age of 10 years and 79% below 20 years (Table 1). The ratio of males to females was 1.2 to 1.0. Twenty percent had partial seizures with or without seizures secondarily generalized. Generalized convulsive seizures with no recognized partial onset were noted in 69%. Seizures were unclassifiable in 11%. Ten percent had seizures every day, 14% had seizures every week, and 33% had seizures every month. Ten percent had burn injuries to different parts of their body. A family history of epilepsy was ascertained in 22%. Possible etiologic factors are shown in Table 2. In 86%, the cause was unknown. Thirteen percent were receiving antiepileptic drugs (AED) therapy, all of them treated with phenobarbital. The rest were receiving herbs (17%) or holy water (7.9%) or used emulates (19%) or made sacrifices (0.7%), 42% had no treatment. EEG was recorded in 53 patients; it was normal in 38%, and demonstrated epileptiform activity in 34%, nonspecific abnormalities in 18%, and paroxysmal rhythms in 11%. Of those with abnormal EEG recordings, 20% had focal unilateral or nonfocal unilateral abnormalities suggestive of a lateralized lesion (partial epilepsy). In some subjects who clinically had only generalized convulsive seizures, the EEG showed focal epileptiform activity. These patients were classified as having partial seizures secondarily generalized. DISCUSSION Table 3 shows the incidence of the study in relation to other population-based studies of epilepsy with or without single unprovoked seizures. We are aware of only one published report on incidence of epilepsy in Africa-the study of Rwiza et al. (7) among the inhabitants of the Ulanga district of Tanzania. They identified 122 persons with onset of epilepsy during a 10-year period, corresponding to an annual incidence rate of 73 in TABLE 2. Possible etiologic factors in incident cases of epilepsy in rural Ethiopia Possible factor No. of cases Percent (%) None 120 (86.3) Head trauma 8 (5.7) Prolonged labof 7 (5.0) Neurological deficit from birthb 2 (1.4) CNS infection 1 (0.7) Stroke 1 (0.7) Total 139 (100) a During birth of the incidence case. Mental retardation.

4 544 R. TEKLE-HAIMANOT ET AL. TABLE 3. Annual incidence rates per 100,000 persons of epilepsy in population-based studies Country Reference, year No. of patients Incidence Comments ~ United States Sweden Fin 1 and Denmark Iceland Poland England France Italy Ecuador China Guam Tanzania Ethiopia Hauser et al. (lo), 1993 Blom et al. (21), 1978 Forsgren (22), 199C Sidenvall et al. (23), 1993 Forsgren et al. (18), 1996 Keranen et al. (24), 1989 Joensen (25), 1986 Gudmundsson (26), 1966 Zielinski (27), 1974 Cockerel1 et al. (28), 1996 Loiseau (29), 1990 Granieri et al. (30), 1983 Placencia et al. (31), 1992 Li et al. (32), 1985 Stanhope et al. (33), 1972 Rwiza et al. (7), 1992 Present study ; ss" included 0-15 years 217 years; ssa included 0-15 years; ssa included 217 years; ss' included 216 years ; ssll included ; ss" included ; ss" included ; ss' included ; SS' includedb a ss, single unprovoked seizures. Provoked afebrile seizures and cases with incomplete diagnostic information included. The incidence is 122 if cases with incomplete diagnostic information are excluded. 100,000. Our annual incidence rate of 64 in 100,000 is slightly lower than the Tanzanian incidence rate. The Ulanga district is the Tanzania region in which Jilek and Jilek-Aall (2) and Jilek-Aall et al. (15) reported a high prevalence of epilepsy. In the study of Rwiza et al. (7) and in our study, incidence was retrospectively assessed by asking the head of household about seizures in all family members, whether dead or alive. The period for recall of seizures was 10 years in the Tanzanian study and 3.5 years in our study. It is likely that the validity of the information is inversely related to the period of recall. The study made in rural Tanzania (7) and the present study made in rural Ethiopia showed a higher incidence of epilepsy than that reported in other continents (excluding studies that have included single or provoked seizures). The prevalence rate of epilepsy in the study area [5.2 in 1,000 inhabitants (6)] and in Nigeria (5) is not high, however, as compared with that in the rest of the world (16). A high incidence rate and normal or low prevalence rate in the same area may be due to a high frequency of spontaneous remissions. It may also be due to a higher mortality in the largely untreated African rural populations. In the investigated area, the annual crude death rate was 16.4 in 1,000 (17) and for persons with epilepsy the death rate was 31.6 in 1,000. The latter rate is based on 20 persons, in 9 of whom death was related to epilepsy (6). The high incidence reported by Rwiza et al. (7) and that in the present study is partly due to the age structure of the studied population. When rates are adjusted to the 1986 population of the United States, the crude incidence of the present study decreases from 64 to 49 in 100,000 (95% CI 46-52) and from 73 to 55 (95% CI 52-58) in the Tanzanian study of Rwiza et al. (7). The highest age-specific incidence was noted in the youngest age group (0-9 years), followed by that in the groups aged and years, for whom rates were comparable. In both the present study and the Tanzanian study (7), incidence rates were considerably higher in the group aged years and considerably lower in the elderly than the rates reported in industrialized countries (10,lS). However, the rates in those >39 years of age in the present study must be interpreted cautiously because they are based on only a few cases. The low rate noted in the elderly is probably due in part to underascertainment in this age group. The reason for the high rates noted in teenagers and young adults is unknown. The most common seizure type in the present study was generalized convulsive seizures. Most of the patients had tonic-clonic seizures. We did not subdivide the generalized convulsive seizures into subgroups because the seizure descriptions in some cases were not sufficiently detailed to allow this. Most studies of newly diagnosed patients show rates of partial seizures to be higher than that of primarily generalized seizures (10,18,19). Reasons for the low proportion of partial seizures in the present study may be that partial-onset manifestations were not

5 INCIDENCE OF EPILEPSY IN ETHIOPIA 545 observed or were later forgotten; therefore, the incidence rates and the proportion of partial seizures reported should be regarded as minimal rates. A larger proportion of primarily generalized epilepsies in the present study as compared with those reported in studies conducted in the industrialized world may be due to demography. The majority of the population (60%) in the present study were children and adolescents aged <20 years. A larger proportion with primarily generalized seizures is found in childhood populations than in adult populations (20). The period from onset of seizures until the identification as an incident case ranged from a few months to 4 years. Most persons with epilepsy had not been treated with AEDs between the onset of their epilepsy and the time of their identification by our team. When our prevalence study was performed, the families were given brief information about epilepsy and were told that it was a disorder that could be treated, often successfully, with medicines available at the local health center. Thirteen percent of the incident cases had begun AED treatment, a percentage higher than the 1.6% of the prevalence population who were receiving AED treatment (6). Yet many of the incident cases had a high seizure frequency and had not received AED treatment at the time they were identified in our study. The explanation for this may be that the previous health education, we provided about epilepsy was insufficient. However, a more plausible reason may be that health services available to these patients are inadequate. For instance, the only health center in the subdistrict does not always stock phenobarbital, the only available and affordable anticonvulsant. The center is also far from many of the villages, and the patients have difficulties in obtaining transportation. Many are forced to walk long distances to visit the clinic. Provision of repeated information to the villagers about epilepsy, as well as provision of improved access to treatment, would probably reduce seizure frequency substantially. Work to provide these has already begun in the area. The high seizure frequency in this largely untreated incidence population explains why 10% of the identified persons with epilepsy, all living in traditional round houses (tukuls) with open fires, sustained burn injuries. REFERENCES 1. Garcia F, de Lao SL, Castillo L, et al. Epidemiology of epilepsy in Guaymi indians from Bocas del Tor0 province, Republic of Panama. Epilepsia 1990;31: Jilek WG, Jilek-Aall LM. The problem of epilepsy in a rural Tanzanian tribe. Afr J Med Sci 1970;1: Goudsmit J, van der Waals FW, Gajdusek DC. 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