Occupational Exposures and Amyotrophic Lateral Sclerosis. A Population-based Case-Control Study

TLDR

This study examined whether occupational exposure to metals, solvents, and agricultural chemicals increases the risk of amyotrophic lateral sclerosis (ALS). Researchers conducted a population‑based case‑control study in three western Washington counties, enrolling 174 newly diagnosed ALS patients and 348 matched controls, and had industrial hygienists blind‑assess lifetime job histories for exposure to metals, solvents, and agricultural chemicals during the period 15 years of age to 10 years before diagnosis. After adjusting for age and education, ever exposure to agricultural chemicals was associated with a two‑fold higher odds of ALS (OR = 2.0, 95 % CI 1.1–3.5), with a stronger association in men (OR = 2.4) and a dose‑response trend, while no associations were found for metals or solvents, suggesting a link between agricultural chemicals and ALS in men.

Abstract

This population-based case-control study was conducted in three countries in western Washington State to evaluate associations between workplace exposures and the risk of amyotrophic lateral sclerosis (ALS). Cases (n = 174) were all newly diagnosed with ALS by neurologists during 1990-1994, and controls (n = 348), who were matched according to age (+/-5 years) and sex, were identified via random-digit dialing or Medicare enrollment files. Four industrial hygienists blindly assessed detailed lifetime job histories for exposures to metals, solvents, and agricultural chemicals. Case-control comparisons were made for jobs held between 15 years of age and 10 years prior to the cases' dates of diagnosis. After adjustment for age and education, ever exposure to agricultural chemicals was associated with ALS (odds ratio (OR) = 2.0, 95% confidence interval (CI) 1.1-3.5); this association was observed separately in men (OR = 2.4, 95% CI 1.2-4.8) but not in women (OR = 0.9, 95% CI 0.2-3.8). Among men, the odds ratio for low exposure to agricultural chemicals (below the median level for exposed controls) relative to no exposure was 1.5 (95% CI 0.4-5.3), and for high exposure, it was 2.8 (95% CI 1.3-6.1) (p for trend = 0.03). Similar analyses based on the panel's assessment of exposures to metals and solvents showed no associations. These findings suggest an association between ALS and agricultural chemicals in men.