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

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.

Dental X‐rays and the risk of intracranial meningioma

“…This method was applied using different time scales, including years before reference date, calendar year, and age. 28,29 Important residual confounding was not identified by age, nor was race (white or other) an important confounder. Given observed associations between education and case-control status and the likelihood of variation in use of dental services by education, we adjusted for education (schooling beyond high school or not).…”

Herbicides and the Risk of Neurodegenerative Disease

“…There was an increased risk of ALS among employees of the Dow Chemical Company who were exposed to the herbicide 2,4-dichlorophenoxyacetic acid versus other Dow employees (Burns et al, 2001). Similar studies have found positive associations for populations exposed to pesticides (McGuire et al, 1997;Qureshi et al, 2006), and the relationship was found to be dependent on dose (Morahan & Pamphlett, 2006). Overall, the relationship tends to be stronger for males than females (McGuire et al, 1997;Morahan & Pamphlett, 2006).…”

“…Similar studies have found positive associations for populations exposed to pesticides (McGuire et al, 1997;Qureshi et al, 2006), and the relationship was found to be dependent on dose (Morahan & Pamphlett, 2006). Overall, the relationship tends to be stronger for males than females (McGuire et al, 1997;Morahan & Pamphlett, 2006). In one study using participants in the American Cancer www.intechopen.com Society's Cancer Prevention Study II, no association between pesticide exposure and ALS was detected (Weisskopf et al, 2009).…”

Case Series Investigation of Amyotrophic Lateral Sclerosis (ALS) Among Former Kelly Air Force Base Workers

“…McGuire et al 27 saw associations, but no dose-response trends, between ALS and the occupational use of cleaning solvents/degreasers as well as alcohols and ketones; however, they found no association between ALS and solvent usage overall. They did, however, find an unexpected association between ALS and insecticides/agricultural chemicals.…”

“…Care must be taken when interpreting the results of many ALS risk factor studies, as most employ a case-control design and depend largely upon subject recall to measure past exposures. Indeed, a couple of studies based on independent, third-party characterizations of past exposures, particularly those related to occupation, found no significant associations between the studied exposures and ALS.26, 27 …”