Analytic, experimental, and theoretical neuroepidemiology: applications to occupational neurology.

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.

Neuroepidemiology. Incidents, incidence, and coincidence.

Neuroepidemiology is concerned with the study of incidents of neurological disease occurring in a community. It deals with the distribution and dynamics of neurological disease in human populations and the factors that affect these patterns. To estimate the magnitude of the disease burden in the population, the neuroepidemiologist calculates indices of disease, such as mortality, prevalence, and incidence. In studying factors associated with disease, the investigator must establish whether the relationship (1) is artifactual, (2) appears to be the result of a chance occurrence or coincidence, and (3) has any biologic significance. The clinical neurologist is the central figure in neuroepidemiologic investigations. The greater the accuracy and completeness of the neurologist's information, the better the quality of neuroepidemiologic studies based on these data.

Paralysis of divergence in an adult with aqueductal stenosis: case report.

Paralysis of divergence was observed in an adult with membranous aqueductal stenosis. This association has not previously been reported, although the clinical syndrome of divergence paralysis has been described in several other neurologic disorders, which are reviewed. Recognition of the clinical syndrome of paralysis of divergence is important, since it may occur as an early sign of increased intracranial pressure and since it has been observed in several conditions that are amenable to treatment.

Tapia's syndrome. The erratic evolution of an eponym.

The syndrome first described in 1904 by the Spanish otolaryngologist, Antonio Garcia Tapia, has been variously interpreted by subsequent authors such that there is little current agreement as to the site of the lesion responsible for the condition or the specific symptoms included in this disorder. The confusion arose in part because Tapia's original patient had associated neurologic findings. Careful review of Tapia's reports reveals (1) that he regarded the syndrome as consisting of ipsilateral hemiplegia of the larynx and tongue with normal function of the soft palate and (2) that he believed the lesion resulting in these signs was outside the CNS.

Primary malignant nervous system neoplasms. Birth cohort effect in the elderly.

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.

Severe dementia. Prevalence and clinical features in a biracial US population.

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.

Functional disability associated with major neurologic disorders. Findings from the Copiah County Study.

The prevalence of functional disability in persons with cerebral palsy, epilepsy, stroke, Parkinson's disease, and severe dementia was assessed in a survey of every household in Copiah County, Mississippi, and all chronic-care institutions serving that county. Of the 23,842 residents evaluated, 246 had moderate to severe functional impairment accompanied by one or more of the aforementioned neurological disorders; 108 were not fully ambulatory; 59 required constant supervision because of cognitive difficulties; 54 were having at least one afebrile seizure monthly; and 25 experienced some combination of these impairments. Overall, prevalence ratios for these impairments increased markedly with age.

Racial differentials in the prevalence of stroke. Copiah County, Mississippi.

Separate surveys of households and chronic-care facilities were conducted in Copiah County, Mississippi. The household survey included screening interviews and a complete census. Board-certified neurologists, using defined diagnostic criteria, examined all consenting persons who were either eligible residents of the chronic-care facilities or household members with interview responses suggestive of stroke. In all, 250 stroke survivors were identified, yielding (as of Jan 1, 1978) a point prevalence ratio of 1,060 per 100,000 inhabitants. Age-adjusted prevalence ratios were higher for men and for blacks. Age-specific prevalence ratios increased with advancing age. Nearly 20% of identified stroke survivors had not received inpatient care for that condition.

Conditions associated with Huntington's disease at death. A case-control study.

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.

Perinatal intracranial hemorrhage. Incidence and clinical features.

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.

Prevalence of essential tremor. Results from the Copiah County study.

This investigation determined the prevalence of essential tremor in a US population. The findings were derived from a large-scale morbidity survey conducted in a rural, biracial Mississippi county (Copiah County). Both the household and the institutionalized populations of the county were included. Results were limited to persons 40 years old or older. Prevalence ratios were higher for women than for men and were higher for whites than for blacks. Age-specific prevalence ratios generally increased with age. The overall prevalence ratio was 414.6 per 100,000 inhabitants.

Epidemiologic study of primary intracranial neoplasms.

The incidence of primary intracranial neoplasms in Rochester, Minn, from 1935 through 1977 is reviewed with regard to whether the tumor was diagnosed because of symptoms arising before death or was found incidentally at autopsy. Among males, the overall age-adjusted incidence rate of cases diagnosed before death was 8.3 per 100,000 population per year, which included a rate of 4.0 for gliomas, 1.2 for meningiomas, and 1.5 for pituitary tumors. Among females, the comparable overall rate was 10.1; that included a rate of 4.1 for gliomas, 2.6 for meningiomas, and 1.7 for pituitary tumors. Of all autopsies on subjects aged 55 years and over, about 1% confirmed or discovered gliomas and slightly more than 1% confirmed or discovered meningiomas.

Prevalence of Parkinson's disease in the Parsi community of Bombay, India.

A door-to-door survey was carried out to screen a community of 14010 people (Parsis living in colonies in Bombay, India) for possible neurologic diseases. High school graduates, social workers, and medical students administered a screening questionnaire that had been shown in a pilot survey to have a sensitivity of 100% for identifying those with Parkinson's disease. Neurologists used defined diagnostic criteria to evaluate individuals positive on the screening survey. There were 46 people (25 men, 21 women) who suffered from Parkinson's disease (328.3 cases per 1000 population). The age-specific prevalence ratios increased consistently with age. Age-adjusted prevalence ratios were slightly higher for men.

Prevalence of essential tremor in the Parsi community of Bombay, India.

A door-to-door survey for neurologic diseases was conducted in a community of 14,010 people (Parsis living in colonies in Bombay, India). Neurologists used defined diagnostic criteria to evaluate persons with positive results on the screening survey. Two hundred thirty-three people (104 men; 129 women) were identified as having essential tremor. The overall prevalence ratio was 1663.1 [corrected] per 100,000 population. Age-specific prevalence ratios increased with age. Age-adjusted prevalence ratios were similar for men and women. To the best of our knowledge, this is the first community-based survey for essential tremor in Asia.

Presenile dementia in Israel.

A nationwide epidemiologic study of presenile dementia of the Alzheimer type (PDAT) with onset through age 60 years was carried out in Israel. The Israeli National Neurologic Disease Register and clinical records of all patients discharged from hospitals between 1974 and 1983 with a neurologic or psychiatric diagnosis suggestive of dementia were reviewed. A total of 71 Jewish patients with onset of PDAT between 1974 and 1978 was ascertained. The age at onset in these patients ranged from 43 to 60 years. The median survival was 8.1 years, with slightly longer survival if onset occurred before age 55 years, even after correction for expected mortality according to age and sex. The average annual incidence rate per 100,000 population at risk was 2.4 in the population aged 40 through 60 years. Although the incidence rates were slightly greater for women, the difference between the rates by sex was not statistically significant. The age- and sex-adjusted incidence of PDAT per 100,000 population was significantly higher in those born in Europe or America (2.9) than in those born in Africa or Asia (1.4). No significant difference in survival was found between these two groups. The curve of the incidence rates by age for PDAT in Israel is continuous with that for senile dementia of the Alzheimer type collected by similar methods elsewhere, which suggests that one disease process may account for both conditions.

A prevalence survey of Parkinson's disease and other movement disorders in the People's Republic of China.

A door-to-door survey was conducted in six cities of the People's Republic of China. A total of 63,195 individuals were sampled during 1983 to determine the prevalence of major neurologic disorders. The survey involved a complete census, followed by a pretested interview and brief screening examination with a high level of sensitivity for detecting individuals with frequently occurring neurologic diseases, including movement disorders. Subjects with abnormal responses or findings were examined by a neurologist. There was 100% cooperation among the study subjects. Twenty-eight individuals alive on prevalence day (Jan 1, 1983) were identified as having Parkinson's disease, yielding an age-adjusted (to the 1960 US population) prevalence ratio of 57 per 100,000 population. All subjects were older than the age of 50 years. After the fifth decade of life, the age-specific prevalence ratios increased with age.

Brain injury due to head trauma. Epidemiology in urban areas of the People's Republic of China.

A door-to-door survey was carried out in six cities of the People's Republic of China during 1983 in a well-defined population of 63,195 to determine the prevalence of frequently occurring neurologic disorders, including brain injury. In the survey, trained health workers conducted a complete census and administered a questionnaire that had been pretested to assure a high level of sensitivity in identifying individuals suffering from brain injury due to head trauma. All those with responses suggesting brain injury were examined by senior neurosurgeons who used uniform diagnostic criteria and reviewed available medical records to establish a diagnosis. There was 100% cooperation with the screening and diagnostic phases of the survey. Based on this investigation, the age-adjusted (to the 1960 US population) prevalence ratio for brain injury due to head trauma is seven per 1,000, and the incidence rate is 56 per 100,000 per year. The ratios and rates are higher in male than female subjects. The main cause of brain injury due to head trauma in the People's Republic of China is bicycle accidents.

Human T-lymphotropic virus type I antibodies in the serum of patients with tropical spastic paraparesis in the Seychelles.

Tropical spastic paraparesis (TSP), a chronic myelopathy of unknown etiology, was studied in the Seychelles. Human T-lymphotropic virus type I (HTLV-I) and human immunodeficiency virus antibodies were determined using an enzyme-linked immunosorbent assay and confirmed with an indirect fluorescent antibody test in serum samples of 20 patients with TSP and 16 controls. Test results indicated that 17 patients (85%) and two controls (transverse myelopathy and clinically probable multiple sclerosis) were positive for HTLV-I. Serum samples of nine healthy controls and five with other neurologic diseases were negative for HTLV-I. No serum samples were positive for human immunodeficiency virus. Estimated relative risk for TSP in those subjects whose serum is positive for HTLV-I antibodies is 40. This result is highly statistically significant. Although primarily associated with adult T-cell leukemia and non-Hodgkin's lymphoma, HTLV-I could also be an etiologic agent of TSP.

Trends in incidence of dementing illness in Rochester, Minnesota, in three quinquennial periods, 1960-1974.

We ascertained the incidence of dementias of all causes between 1960 and 1975 among citizens of Rochester, Minnesota. Study of all medical records yielded incidence rates for the quinquennial periods of 1960-1964, 1965-1969, and 1970-1974. In the population at risk (30 years or older), the age-adjusted rates (per 100,000 population/year) for Alzheimer's disease (clinically diagnosed or pathologically confirmed, or both) in the three periods were: 104.9, 80.8, and 96.6. The rates for dementia of all causes were: 160.6, 122.0, and 136.8. Calculation of 95% confidence intervals showed that the incidence rate for dementia or Alzheimer's disease has not changed in this 15-year period in Rochester, Minnesota. Assuming no demented patients younger than 29 years, the incidence rates in the three quinquennial periods for all dements were 79.4, 60.3, and 67.7; for Alzheimer's disease they were 51.9, 40.0, and 47.8.

Motor neuron disease in the United States, 1971 and 1973-1978: patterns of mortality and associated conditions at the time of death.

Mortality rates for deaths "due to" and "with" motor neuron disease are presented for the first time. Age-specific mortality rates increase with age until 70 to 74 years and then decline. There appear to be no major differences by race in the age-adjusted mortality rates, but these rates are higher for males both white and nonwhite. A case-control study of all deaths with amyotrophic lateral sclerosis (ALS) was conducted for deaths due to ALS in the year 1971. Conditions associated with ALS at the time of death include pneumonia and bronchopneumonia, symptoms referable to respiratory system, superficial injury to shoulder and upper arm, essential benign hypertension, chronic skin ulcer, and malnutrition. No association was found between ALS and malignancies, Parkinson's disease, or dementia.