title: What we truly know about occupation as a risk factor for ALS: a critical and systematic review.
abstract: Occupational and environmental exposures may contribute to the risk of developing sporadic amyotrophic lateral sclerosis (ALS). To summarize the available evidence, a systematic review of the literature on occupation as a potential determinant of ALS was performed according to the MOOSE guidelines. From MEDLINE, EMBASE, CINAHL, and Cochrane databases, selected studies were methodologically appraised according to Armon's classification system for ALS risk factor studies. Each occupation studied was reclassified according to the International Standard Classification of Occupations (ISCO-88). The vote-counting method was applied to summarize the data. Of 3773 potentially relevant studies, 51 were initially included. Of these, 12 studies provided risk estimates for individual occupations--one case-control, two register-based case-control, and nine register-based cohort studies. All studies fell into Armon's level of evidence class IV, indicating methodological limitations. Due to the heterogeneity of study methodology, data could not be pooled. The vote-counting method revealed several candidate occupations: veterinarians and other health workers, athletes, hairdressers, power-production plant, electrical and military workers. However, well designed studies with standardized assessment of occupation are needed to provide a more definitive answer about exogenous risk factors of ALS.
authors.affiliation: Department of Neurology, Rudolf Magnus Institute of Neuroscience, University Medical Centre, Utrecht, The Netherlands.
authors.forename: Nadia A
authors.initials: NA
authors.lastname: Sutedja
authors.forename: Kathelijn
authors.initials: K
authors.lastname: Fischer
authors.forename: Jan H
authors.initials: JH
authors.lastname: Veldink
authors.forename: Geert J M G
authors.initials: GJ
authors.lastname: van der Heijden
authors.forename: Hans
authors.initials: H
authors.lastname: Kromhout
authors.forename: Dick
authors.initials: D
authors.lastname: Heederik
authors.forename: Mark H B
authors.initials: MH
authors.lastname: Huisman
authors.forename: John J H
authors.initials: JJ
authors.lastname: Wokke
authors.forename: Leonard H
authors.initials: LH
authors.lastname: van den Berg
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000209:etiology* / Q000235:genetics; D016208:Databases, Factual; D006801:Humans; D016273:Occupational Exposure / Q000009:adverse effects*; D009790:Occupations; D012196:Review Literature as Topic; D018570:Risk Assessment; D012307:Risk Factors; D014481:United States