Occupational exposure to magnetic fields and electric shocks and risk of ALS: The Swiss National Cohort

Abstract

Amyotrophic lateral sclerosis (ALS) has been associated with exposures in so-called ‘electrical occupations’. It is unclear if this possible link may be explained by exposure to extremely low-frequency magnetic fields (ELF-MF) or by electrical shocks. We evaluated ALS mortality in 2000–2008 and exposure to ELF-MF and electrical shocks in the Swiss National Cohort, using job exposure matrices for occupations at censuses 1990 and 2000. We compared 2.2 million workers with high or medium vs. low exposure to ELF-MF and electrical shocks using Cox proportional hazard models. Results showed that mortality from ALS was higher in people who had medium or high ELF-MF exposure in both censuses (HR 1.55 (95% CI 1.11–2.15)), but closer to unity for electrical shocks (HR 1.17 (95% CI 0.83–1.65)). When both exposures were included in the same model, the HR for ELF-MF changed little (HR 1.56), but the HR for electric shocks was attenuated to 0.97. In conclusion, there was an association between exposure to ELF-MF and mortality from ALS among workers with a higher likelihood of long-term exposure.

Key words::

• Amyotrophic lateral sclerosis
• occupational exposure
• magnetic fields
• electric shocks

Acknowledgements

We would like to thank Judith Lupatsch for help with inspection of the ISCO88 codes, and Joseph Bowman for making the original ELF-MF JEM available, and the Swiss Federal Statistical Office, whose support made the Swiss National Cohort possible. We also thank Kali Tal for her editorial assistance.

Declaration of interest: All authors declare that they have no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

This study was supported by ZonMW within the programme Electromagnetic Fields and Health Research, The Netherlands (grant No. 85800001). The Swiss National Cohort is supported by the Swiss National Science Foundation (grant No. 33CS30_134273/1).

Supplementary material available online

Supplementary Tables I and II material to be found online at http://www.informahealthcare.com/doi/abs/10.3109/21678421.2014.954588.