To the Editor.—
Kilness and Hochberg reported a cluster of four cases of amyotrophic lateral sclerosis (ALS) in one South Dakota county (population 4,060) over a ten-year period and suggested that this might be related to the high selenium content of the local soil. Little is known about the cause of ALS, and any possible leads are welcome. However, a more thorough review of the literature and a more careful analysis of their data might have led to a more cautious statement than the one that has engendered deep concern in the local population and other populations where the soil contains relatively large concentrations of selenium (Rochester Post Bulletin, July 6, 1977, p 21).The average annual incidence rate for ALS in the United States is about 1.6 per 100,000 population1; thus, about 0.6 cases would be expected in the county over the ten-year period if the age and sex
Kurland LT. Amyotrophic Lateral Sclerosis and Selenium. JAMA. 1977;238(22):2365–2366. doi:10.1001/jama.1977.03280230029005
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