25 years of neuroepidemiology in the Americas

In the Western Hemisphere, prior to 1950, there were few reliable data on the incidence, geographic distribution or population patterns of diseases of the nervous system. Impressions of prevalence were generally derived from the European literature and from a variety of case reports and relative frequencies based on clinic or hospital admissions or selected autopsy series. Since such data from different sources generally defy comparison, it has been necessary to develop data sources for defined populations to provide incidence and prevalence rates. Such an effort, initially concerned with multiple sclerosis, was launched in 1950 by NIH. International mortality statistics were also collected and analyzed and intensive population surveys in the United States and Canada were planned and carried out. In time, such efforts were extended to cover a wide variety of other chronic and subacute diseases of the nervous system, and support was provided by NIH and voluntary agencies for studies in many other countries. Independently, population studies were developed at various Universities and health care facilities in Latin America. ISSSTE in Mexico City provided a broad experience on multiple sclerosis, ALS, epilepsy, stroke and brain tumor; studies developed in the West Indies on Jamaican Neuropathy; and there were studies in several countries on cysticercosis, Chagas' disease and epilepsy. Also notable are recent studies in Guatemala and plans for geographic comparisons over the broad range of latitude in Chile. The advantages and limitations of mortality statistics will be discussed. The priorities in the selection of the disorders which were to be studied, the procedures which were developed, and the highlights of the results of such investigations will be presented. In addition to descriptive population surveys, case control comparisons and prospective studies are also being developed which seek to identify the risk factors or etiologic determinants that may account for the population pattern which have been observed.