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Amyotrophic lateral sclerosis mortality among native‐born and migrant residents of California and Washington

Numerous descriptive epidemiologic studies of amyotrophic lateral sclerosis (ALS) have attempted to uncover patterns of disease distribution that might provide a suggestion as t o the etiology of this disease. The discovery of a relationship between latitude and the frequency of multiple sclerosis has stimulated the investigation of geographic patterns in the distribution of ALS. A great proportion of this research has been based o n national and international mortality statistics because of the difficulty of obtaining accurate prevalence and incidence data for a relatively rare disease. These studies suggest that, with the exception of foci of disease o n the Manana Islands in the Western Pacific’ and on the Kii Peninsula, Japan,’ rates of ALS have been remarkably uniform in the countries Statistics on U.S. mortality likewise suggest n o state or regional differences in mortality rates.3” Because mortality studies of this type depend on comparison of rates in different populations, interpretation of the results must take into account geographic variations in medical care, diagnostic facilities, coding of deaths, and death certification. The present study is an investigation of death rates from ALS in nativeborn Californians and Washingtonians and in migrants t o these states from different regions of the continental United States. This design allows for a comparison of rates among people who were born in various areas of the country but were subject t o similar standards of medical care and certification at the time of death.