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The Mayo Clinic medical records system and records-linkage system have been used to study trends in the incidence of stroke in Rochester, Minnesota, for comparison with U.S. stroke mortality trends. This study extends the observations back through 1935. The average annual incidence rate for the period 1935 to 1944 was 188 and 179 per 100,000 population for men and women, respectively--not significantly different from 200 for men and 178 for women for the period 1945 to 1954. The blood pressure level in these patients did not affect probability of survival or recurrent stroke. The trend in the incidence rate of stroke for women showed no change for the 20 years from 1935 to 1954, after which there was a gradual decline. For men there was little change until 1969, after which there was a sharp decline. We suggest that the gradual decline in U.S. stroke mortality rates for this early period may include an artifact introduced by changing codes and changing fashions of diagnosis.

The available evidence suggests that there may be two subtypes of AD-- inherited and noninherited. Inherited AD may have certain characteristics, e.g. younger age at onset and some clinical signs or symptoms, which distinguish them from noninherited cases. It is possible that the noninherited type of AD may also have a similar genetic defect as the inherited kind, the only difference being that in one case the defect is inherited from the parents and in the other the defect arises de novo during embryogenesis. An environmental factor operating during embryogenesis may be responsible for causing a genetic defect which later manifests as noninherited AD. Currently, however, there is no precise way to separate these two subtypes. The exact proportion of all cases of AD which are inherited on a genetic basis is not known, but it must be small. The mode of inheritance of genetic AD is not known. It must be emphasized that the subtypes of inherited and noninherited AD are not synonymous with the older categorization of AD into presenile and senile AD.

"Hot water epilepsy" (HWE), precipitated by a bath or shower in hot water, has been described infrequently in the literature. We report 279 cases of HWE that were seen between 1980 to 1983 in Bangalore, South India. We found HWE to be more common in children, with cases more frequent among male than female patients (2.6:1). Complex partial seizures constituted the main clinical presentation (67.0%); HWE accounted for 4.4% of all complex partial seizures and generalize tonic-clonic seizures seen at our center during the 1980-1983 period. Although prognosis seems favorable 25.4% of our patients developed nonreflex epilepsy within 1-3 years. They were managed with antiepileptic drugs and the use of lukewarm water for bathing.

Epidemiologic studies of epilepsy pose a number of methodologic challenges with regard to the definition, classification, and identification of cases. The use of different procedures to address these difficulties makes it imperative to exercise great caution in comparing the results of such studies. Epidemiologic investigations have been consistent in demonstrating that epilepsy is a major neurologic disease throughout the world. Analytic investigations which are beginning to identify risk factors must be continued in order to initiate broad and effective programs of prevention and control.

In a case-control study we compared 155 Nigerians affected by epilepsy, with an equal number of controls matched for age and sex, with the aim of identifying risk factors of epilepsy. Febrile convulsions and head trauma (with odds ratios of 11.0 and 13.0, respectively) were significant risk factors (p less than 0.01). Childhood immunizations were found associated with a decreased risk of epilepsy. None of the following factors was significantly associated with epilepsy: hemoglobinopathy, venereal disease, use of psychotropic drugs or alcohol, and cerebrovascular disease. Preventive measures for the risk factors identified are suggested as ways of reducing the burden of epilepsy in Nigeria.

To identify conditions associated with reduced survival in patients with Huntington's disease, we studied all 1978 US death certificates on which Huntington's disease (331.0 in the International Classification of Diseases, eighth revision) was listed. For each of the 495 cases identified, two control deaths were matched by age, race, sex, county, and year of death. Pneumonia, choking, nutritional deficiencies, and chronic skin ulcers were increased in cases relative to controls.

Case reports and case series dealing with multiple primary malignant neoplasms provided useful criteria for defining and documenting this phenomenon. The formation of tumor registries greatly aided in identifying a sufficient number of multiple primary cancer patients and facilitated case-control comparisons. Reports of two or more neoplasms occurring together in the same individual do not constitute proof of a significant association; the tumors must be shown to occur together more frequently than expected by chance. The person-years approach applied to data derived from a well-defined population makes it possible to compare the observed and expected number of subsequent primary cancers. The results of the most sophisticated procedures are no better than the quality of the data, however, and one must critically examine possible sources of bias before accepting statistical significance as representing biologic significance.

Tropical myeloneuropathies include tropical ataxic neuropathy and tropical spastic paraparesis. These disorders occur in geographic isolates in several developing countries and are associated with malnutrition, cyanide intoxication from cassava consumption, tropical malabsorption (TM), vegetarian diets, and lathyrism. TM-malnutrition was a probable cause of myeloneuropathies among Far East prisoners of war in World War II. Clusters of unknown etiology occur in India, Africa, the Seychelles, several Caribbean islands, Jamaica, and Colombia. Treponemal infection (yaws) could be an etiologic factor in the last two. Tropical myeloneuropathies, a serious health problem, are multifactorial conditions that provide unsurpassed opportunities for international cooperation and neurologic research.

The purpose of this investigation was to document the prevalence of severe dementia among different racial groups residing in the same community--Copiah County, Mississippi. Both household and institutionalized populations were included. For either sex, the prevalence ratios of all severe dementia and clinically diagnosed severe senile dementia of the Alzheimer's type were at least as large among blacks as among whites. For either race, the corresponding prevalence ratios were greater in females. For each race and sex, the corresponding prevalence ratios increased with advancing age. Finally, in the population studied, approximately 1% of individuals 40 years old or older had severe dementia. This figure increased to 7% for individuals 80 years old or older.

All eligible adult cases of completed ischemic stroke (N = 112) derived from a prevalence survey of the Parsi community in Bombay, India, served as the basis of a case-control study of risk factors. The stroke morbidity rate in this group was similar to that reported for North America. A control subject free of stroke was selected randomly from the same population and matched to each case by age and sex. Information was obtained on various risk factors. Hypertension, both by history (odds ratio = 10.8) and by examination (odds ratio = 2.1), had a statistically significant association with stroke (p less than 0.01). This is one of the first community-based case-control studies of stroke in a large developing country.

The only measures of morbidity for Guillain-Barré syndrome in well-defined populations in the continental United States come from Olmsted County, Minnesota, and San Joaquin County, California. The estimated incidence rates are between 1 and 2 cases per 100,000 population per year. Despite the hazards of generalizing from such small samples, these are the only estimates available. Large case series have suggested that the syndrome is more common in males, that it may occur at any age, and that it is frequently associated with some antecedent infection. Only two case-control comparisons have been carried out which reveal an association between Guillain-Barré syndrome and an infection 1 month prior to onset of neurological symptoms. A recent survey of four states in the United States revealed that the risk of Guillain-Barré syndrome among individuals receiving immunization against influenza A/New Jersey is 7.3 times the risk among the nonvaccinated. Aside from these investigations and one study linking Guillian-Barré syndrome and high antibody titers to cytomegalovirus, adequate epidemiologic studies to test suggested etiologic hypotheses have not yet been carried out. The rarity of the condition and the variations in its clinical presentation and course pose certain problems for epidemiologic investigations. Strategies for overcoming these difficulties are discussed.

Birth and perinatal records from all medical facilities serving the Rochester, Minn population from 1965 through 1974 were reviewed for cases of intracranial hemorrhage. Among a total of 10,850 live births, 12 documented cases of hemorrhage were found, yielding an average rate of occurrence of 1.1/1,000 live births. To investigate the role of some 30 potential risk factors, a case-control study was undertaken. Only prematurity and respiratory distress syndrome (RDS) were significantly associated with intracranial hemorrhage. This study demonstrates that neonatal intracranial hemorrhage is relatively common, associated with prematurity and RDS, difficult to recognize clinically, and characterized by poor prognosis.

Current epidemiologic studies of the inherited ataxias are limited by complex and confusing systems of nomenclature and by the lack of minimal diagnostic criteria. Despite the difficulties of comparing one study to another, most descriptive investigations provide a prevalence estimate of less than 6 cases/100,000. In isolated, inbred populations, a prevalence as high as 23 cases/100,000 has been reported. Neuroepidemiologic techniques and current knowledge concerning the epidemiology of the inherited ataxias can be applied to future studies in three broad areas--definition, classification, and etiology. Future etiologic investigations based on a goal-oriented, collaborative effort following a case-control format offer the greatest likelihood of success.

Analytic neuroepidemiologic studies can be particularly valuable in identifying factors associated with either a high or low risk of disease in the industrial environment. Intervention strategies can then be formulated and the effectiveness of such programs can be tested using the techniques of experimental neuroepidemiology. By constructing mathematical models (theoretical neuroepidemiology) of actual situations, it is possible to attempt to predict how the frequency of disease will change if certain aspects of the environment are modified.

Mortality rates for deaths 'due to' and 'with' hereditary ataxias are presented for the first time. Age-adjusted mortality rates were higher for whites than for nonwhites of either sex, and for men in both racial groups. Age-specific mortality rates for whites showed a peak for 'hereditary spinal ataxia' in the 20-29 age group. For the other types of ataxias they were low until age 40 and increased thereafter. Heart diseases were a frequent cause of death in people dying 'with' hereditary ataxias. The median survival (from birth) for hereditary spinal ataxia in whites was 35 years.

Results for non-simultaneously diagnosed malignant tumors from Connecticut indicate that individuals with one malignant neoplasm have 1.29 times the risk of developing a new independent primary tumor when compared to individuals who never had cancer (P less than 0.01). However, the increased risk of multiple primary tumors is highly selective on a site-specific basis. Table 135 presents Connecticut Registry data indicating the risk of a subsequent primary malignancy by anatomic site of the later primary in patients with a first primary cancer. Tables 136 and 137 present tabulations for anatomic sites with statistically significant excesses and deficiencies, with an analysis by time interval between the two malignancies. Finally, Table 138 presents figures showing histologic confirmation for site-group paris with significant excesses of observed-over-expected later primary malignant neoplasms. The reader should bear in mind that just as the risk of subsequent primaries varies with the anatomic site of the subsequent primary (Table 135), the risk is also highly dependent upon the anatomic site of the first primary cancer (Chapters 6-12).

A census, uniform screening questionnaire, and simple screening neurologic examination were administered in a door-to-door survey to residents of Quiroga, Ecuador, a rural community in the Andes Mountains. The screening procedures had been pretested to assure a high level of sensitivity for detecting children and adults with major neurologic disease. A total of 1,113 participated in the study. Of these, 399 had responses or findings suggesting the presence of neurologic disease. These individuals were then examined by a neurologist, who used fixed diagnostic criteria. The prevalence ratios (per 1,000) for the most common neurologic conditions identified in this survey are: recurrent/persistent severe headache = 68.3, and epilepsy = 17.1.

This article addresses three questions to be answered during the planning of prevalence surveys of chronic disorders in geographically defined populations: (a) Should personal interviews be used alone (i.e. without accompanying physical examinations) to find and confirm cases in a household population? (b) As an alternative means of identifying cases, is it adequate to review patient records from hospitals and clinics serving the population to be surveyed? (c) Should population members residing in institutions of long-term care be made ineligible for the anticipated survey? Data on major neurologic disorders, obtained from the Copiah County Study, are used to suggest caution in answering any of these questions in the affirmative, since in particular circumstances the consequences for the intended research may be serious or even disastrous. For example, with 42% of Parkinson's disease cases diagnosed for the first time during the study, a casefinding approach solely through medical-care providers would have been highly questionable for that disorder.

In a Nigerian town with a stable population of 20,000, a door-to-door survey was conducted, using a questionnaire involving a complete census and a simple neurological evaluation which had previously showed a 95% sensitivity and an 80% specificity for detecting neurological disease. Positive responders were evaluated and categorised, using agreed criteria for diagnoses. Nearly 100% cooperation was obtained. Life prevalence ratio for at least one episode of headache was 51/1000. Crude point prevalence ratio for migrainous headache was 5.3/100, and peak age-specific ratio was in the first decade. Prevalence ratio for epilepsy was 533/100,000 and peak age-specific prevalence ratio occurred in the 5-14 years age groups. The prevalence ratio for peripheral nerve disorders was 268/100,000, and age-specific prevalence ratio for tropical neuropathy increased with age. Prevalence ratio for stroke was rather low at 58/100,000, but was probably due to the people's attitude to the disabled elderly and high mortality of stroke which showed annual mortality rate of 70/100,000 which increased with age to 1519/100,000 per year in the eighth decade. Crude prevalence ratios (cases per 100,000) for others are 112 for neurological complications (including sciatica) of spondylosis, 15 each for poliomyelitis, motor neurone disease, development speech disorders, 10 each for syncope, hereditary neuropathies. Parkinson's disease, benign essential tremor, primary cerebellar degeneration, cerebral palsy, mental retardation, organic psychosis (probable intracranial tumor) and 5 each for muscular dystrophy, pyomyositis, spina bifida occulta, alcohol dependence and cerebral malaria. The implications of the findings are important for development of community neurological services in the developing countries.

To determine the prevalence of major neurologic disorders, a door-to-door survey was conducted in six cities of the People's Republic of China during 1983 in a well-defined population of 63,195. The survey included a complete census and a screening interview together with an examination having high sensitivity for detecting individuals with frequently occurring neurologic disorders, including epilepsy. All individuals with responses or findings suggesting neurologic disease were examined by senior neurologists using standardized diagnostic criteria. There was 100% cooperation among the study subjects. Two hundred eighty-nine individuals alive on prevalence day (January 1, 1983) were identified as having epilepsy, yielding a lifetime age-adjusted (to the 1960 U.S. population) point prevalence ratio of 4.4/1,000. There were 16 people who developed epilepsy in the sample population during 1982, providing an age-adjusted incidence rate of 35/100,000 per year. The most frequent type identified was generalized convulsive seizures. Brain injury, intracranial infection, and cerebrovascular disease, in that order, were the leading putative causes of epilepsy.

All primary intracranial neoplasms diagnosed between 1935 and 1964, inclusive, in the well-defined populations of children under age 15 residing in the state of Connecticut and the city of Rochester, Minnesota, formed the basis for this study. The tumors occurring in this group were characterized by histologic type and by the patient's sex and the age when the tumor occurred. In Connecticut, over the 30-year period, a primary intracranial neoplasm was diagnosed in 380 patients in a mean population of 582,286 children, yielding an average annual incidence rate of 2.17 cases/100,000 population per year. Of the microscopically confirmed tumors, the most common, in order, were medulloblastoma (24.2%), astrocytoma (20.6%), glioblastoma (20.3%), ependymoma (6.5%), craniopharyngioma (5.6%) and meningioma (4.6%). These figures contrast sharply with the corresponding frequency of these tumors in the adult Connecticut population. In Rochester during the same years, 12 primary intracranial neoplasms occurred in a mean population of 7,981 children, yielding an average annual incidence rate of 5.01 cases/100,000 population per year.

Descriptive epidemiologic studies demonstrate that the risk of dementia in general and of Alzheimer's disease in particular increases with advancing age, and the risk appears to be slightly greater among women. There is no firm epidemiologic evidence to suggest that Alzheimer's disease represents two distinct conditions. Demographic projections indicate that the number of affected individuals is expected to grow as the elderly segment of our population increases. Analytic epidemiologic studies have yielded a number of positive findings, including an excess of dementia, Down's syndrome, and lymphoma in the relatives of index cases of Alzheimer's disease and a greater than expected frequency of head trauma and thyroid disease among those with Alzheimer's disease. Results have not been consistent from study to study and await further confirmation. It is hoped that findings of future analytic investigations will provide much needed information required for the development of rational programs of treatment and prevention of this major health problem.

Average annual age-adjusted mortality rates for epilepsy from 33 countries for 1967-1973 were calculated and compared to earlier data (when available) from the 1950s. Rates during 1967-1973 range from 0.6 deaths/100,000/year (Denmark) to 4.0 deaths/100,000/year (Portugal). Countries in Latin America generally have high rates. With few exceptions, epilepsy mortality rates have declined over time. For each country studied, the rates are higher for males. As prevalence surveys are implemented throughout the world, we shall no longer need to rely on mortality statistics to provide some indication of the patterns of epilepsy on an international basis.

To determine which conditions may be associated with reduced survival in patients with Alzheimer's disease, we studied all death certificates in the United States for 1978 on which senile and presenile dementia (ICDA 290, N = 7,195) was mentioned. Each case was compared with two control deaths. Differences in the frequency of listing on the death certificates for the following conditions reached statistical significance: infections, trauma, nutritional deficiency, chronic ulcer of skin, foreign body in pharynx, cataract, glaucoma, blindness, deafness, Parkinson's disease, and epilepsy. There seem to be many preventable and treatable disorders in patients with senile and presenile dementia.

In 1984-85, the authors assessed the reliability of surrogate respondents to provide interview data for the specific items of a case-control study of Alzheimer's disease conducted in Italy. For all questions of the interview, responses of 52 non-demented subjects were compared to responses of their next-of-kin. In 21-27% of the pairs the next-of-kin was unable to answer questions about general anesthesia, antacid drug use, and age of mother and father at index birth. However, the surrogate respondent was able to answer 45 of 57 tested items with agreement greater than 80%. Questions about use of hard liquor and behavior pattern yielded agreement of 71-75%, while those about number of jobs, and number of cigarettes per day yielded 62-63% agreement. For those who provided information about antacid drug use, agreement was poor. These findings are encouraging for the use of next-of-kin respondents in case-control studies of Alzheimer's disease or other neurologic conditions for which the subject cannot provide historical information.

Parkinson's disease (PD) has been proposed to result from the interaction of aging and environment in susceptible individuals. Defective metabolism of debrisoquine, inherited as an autosomal recessive, has been associated with this susceptibility. In 35 PD patients and 19 age-matched controls, no significant differences in debrisoquine metabolism were found, although a trend to impaired metabolism was noted in patients with disease onset less than or equal to 40. Foci of PD patients were associated with rural living and well water drinking, or rural living coupled with market gardening or wood pulp mills. In a questionnaire survey, patients with PD onset less than or equal to age 47 were significantly more likely to have lived in rural areas and to have drunk well water than those with onset greater than or equal to age 54 (p less than or equal to 0.01). Because of population mobility in North America, a case-control study designed to test environmental, occupational, dietary and other proposed risk factors for PD was conducted in China, where the population is more stationary and the environment more stable. No significant differences in incidences of head trauma, smoking or childhood measles were found between patients and controls.

Current data indicate that mortality for primary malignant nervous system neoplasms (NSNs) provides a fairly accurate index of incidence. Average annual age- and sex-specific death rates among whites for primary malignant NSNs in the 48 contiguous United States from 1940 through 1975 showed a marked cohort effect among the elderly of either sex. For white men aged 60 through 64 years, mortality increased steadily from 5.3 per 100,000 per year for those born in 1880 to 16.1 per 100,000 per year for the 1910 cohort. No definite cohort effect was seen in the young. The increase in mortality could be due to better diagnosis and more complete case ascertainment for deaths due to primary malignant NSNs, but further studies are required to distinguish a real from an artifactual increase in mortality.