Amyotrophic lateral sclerosis and occupational heavy metal exposure: a case-control study.

A retrospective case-control study of occupational heavy metal exposure was conducted using 66 amyotrophic lateral sclerosis (ALS) patients and 66 age- and sex-matched controls. Cases were ascertained primarily through a neurology support and research clinic. The self-administered questionnaire probed potential exposure to nine heavy metals: aluminum, lead, lead alkyl, magnesium, manganese, mercury, mercury alkyl, nickel and selenium. Using McNemar's test and a Mantel Haenszel extended analysis, no association was found between heavy metal exposure and the pathogenesis of ALS in this patient population. Demographic factors, fracture history, immunizations, travel and other variables were similar in ALS patients and controls.