Objectives To examine the associations of specific occupations and occupational exposures with the risk of amyotrophic lateral sclerosis (ALS) in the Swedish population.
Methods A nested case–control study was conducted in Sweden. Patients with ALS diagnosed during 1991–2010 (n=5020) were identified from the National Patient Register and 5 controls per case (n=25 100) were randomly selected from the general Swedish population, individually matched to cases by birth year and sex. Occupational history was obtained from the Swedish censuses in 1970, 1980 and 1990. The Nordic Occupational Cancer Study Job Exposure Matrix was used to identify exposures related to individual occupations. Conditional logistic regression was used to estimate ORs and their 95% CIs.
Results Higher risk of ALS was associated with precision-tool manufacturing (OR 1.68, 95% CI 1.11 to 2.52) and glass, pottery and tile work (OR 1.76, 95% CI 1.03 to 3.00), whereas lower risk was associated with textile work (OR 0.44, 95% CI 0.21 to 0.91). None of the examined occupational exposures were associated with ALS risk overall. However, among individuals younger than 65 years of age, an association with a higher risk of ALS was found for formaldehyde (OR 1.29, 95% CI 1.00 to 1.65), and an association with a lower risk of ALS was found for methylene chloride (OR 0.49, 95% CI 0.26 to 0.93).
Conclusions We identified several occupations and occupational exposures that may be associated with the risk of ALS in Sweden. Occupational history obtained from censuses every 10 years remains a limitation of the study.
- Amyotrophic Lateral Sclerosis
- Job Exposure Matrix
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Contributors TLP, FK, CL, MF, CEW, PS, WY, FF and DPS were involved in study concept and design. TLP, FK, CEW, CL and FF were involved in study analysis and interpretation of data. TLP and FF were involved in drafting of the manuscript . All authors were involved in critical revision of the manuscript.
Funding This study was supported by the Swedish Research Council (SIMSAM grant No. 80748301 and Grant No. 2015-03170), FAS (grant No. 2011-0172), the EU Joint Programme—Neurodegenerative Disease Research (JPND; http://www.jpnd.eu), the Swedish Society for Medical Research (SSMF), the Karolinska Institutet, and the Intramural Research Program of The National Institute of Environmental Health Sciences, National Institutes of Health (Z01-ES-049005).
Competing interests None declared.
Patient consent Obtained.
Ethics approval This study was approved in Stockholm, Sweden, by the Regional Ethical Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.