ALS and heavy metals: a pilot case-control study.

We conducted a case-control study of suspected risk factors for ALS among referral patients seen at the Mayo Clinic. Responses to questions about demographic factors, diet, medical history, travel, infectious disease, and other variables were similar in ALS patients and controls. In all but a few items, the responses of the cases and controls did not differ significantly. A significant level of shared exposure to an exogenous agent or environmental insult among cases was noted mainly for heavy metals.