The relation between amyotrophic lateral sclerosis and inorganic selenium in drinking water: a population-based case-control study.

ABSTRACT: BACKGROUND: A community in northern Italy was previously reported tohave an excess incidence of amyotrophic lateral sclerosis among residents exposedto high levels of inorganic selenium in their drinking water. METHODS: To assess the extent to which such association persisted in the decade following itsinitial observation, we conducted a population-based case-control studyencompassing forty-one newly-diagnosed cases of amyotrophic lateral sclerosis andeighty-two age- and sex-matched controls. We measured long-term intake ofinorganic selenium along with other potentially neurotoxic trace elements.RESULTS: We found that consumption of drinking water containing one or more mcg/lof inorganic selenium was associated with a relative risk for amyotrophic lateralsclerosis of 5.4 (95% confidence interval 1.1-26) after adjustment forconfounding factors. Greater amounts of cumulative inorganic selenium intake wereassociated with progressively increasing effects, with a relative risk of 2.1(95% confidence interval 0.5-9.1) for intermediate levels of cumulative intakeand 6.4 (95% confidence interval 1.3-31) for high intake. CONCLUSION: Based onthese results, coupled with other epidemiologic data and with findings fromanimal studies that show specific toxicity of the trace element on motor neurons,we hypothesize that dietary intake of inorganic selenium through drinking waterincreases the risk for amyotrophic lateral sclerosis.