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Original article
Population-based study of amyotrophic lateral sclerosis and occupational lead exposure in Denmark
  1. Aisha S Dickerson1,2,
  2. Johnni Hansen3,
  3. Aaron J Specht2,
  4. Ole Gredal3,
  5. Marc G Weisskopf1,2
  1. 1 Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
  2. 2 Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
  3. 3 Occupation Research Unit, Institute of Cancer Epidemiology, Danish Cancer Society Research Center, Copenhagen, Denmark
  1. Correspondence to Dr Aisha S Dickerson, Chan School of Public Health, Environmental and Occupation Medicine and Epidemiology Division of the Department of Environmental Health, Boston MA 02115, USA; adickerson{at}


Objectives Previous research has indicated links between lead (Pb) exposure and increased risk of neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS). In this study, we evaluated the association between occupational Pb exposures and ALS.

Methods ALS cases were ascertained through the Danish National Patient Registry from 1982 to 2013 and age and sex-matched to 100 controls. Using complete employment history since 1964 from the Danish Pension Fund, cumulative Pb exposure was estimated for each subject via a Danish job exposure matrix. Associations were evaluated using conditional logistic regression analyses and stratified by sex.

Results For men with >50% probability of exposure, there was an increase in odds of ALS for exposures in the 60th percentile or higher during any time 5 years prior to diagnosis (aOR: 1.35; 95% CI 1.04 to 1.76) and 10 years prior to diagnosis (aOR: 1.33; 95% CI 1.03 to 1.72). No significant associations were observed in women, and there were no linear trends seen for Pb exposures for either sex.

Conclusions Our study indicates an association between consistently higher occupational Pb exposures and ALS. These findings support those of previously reported associations between ALS and specific occupations that commonly experience Pb exposure.

  • amyotrophic lateral sclerosis
  • motor neurone disease
  • lead
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  • Contributors MGW and JH designed the study and directed its implementation. JH and OG gathered data. ASD performed data analysis and drafted the article. MGW, JH and AJS revised the manuscript.

  • Funding This work was supported by the National Institute of Environmental Health Sciences (grants R01 ES019188 and P30 ES000002 to MGW). ASD was supported in part by a National Institutes of Health training grant (grant T32 ES007069).

  • Competing interests None declared.

  • Ethics approval This study was approved by the Danish Data Protection Agency. Because this study was a secondary analysis, it was determined to be exempt from full review by the Harvard T.H. Chan School of Public Health Institutional Review Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Patient consent for publication Not required.

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