Previous work has suggested an increase in risk of amyotrophic lateral sclerosis (ALS) and Alzheimer’s disease among workers exposed to extremely low-frequency magnetic fields (ELF-MF). We evaluated the relation between ELF-MF from occupational exposures and mortality from neurodegenerative diseases.
The study was based on a cohort of Swedish engineering industry workers, comprising 537,692 men and 180,529 women. The cohort was matched against the 3 most recent censuses and The Causes of Death Registry. Levels of ELF-MF exposure were obtained by linking occupation according to the censuses to a job exposure matrix. We used 4 levels of exposure and considered both the primary and contributing causes of death, 1985-96.
The risk of Alzheimer’s disease as primary or contributing cause of death increased with increasing exposure to ELF-MF among both men and women, with a relative risk (RR) of 4.0 and a 95% confidence interval (95% CI) of 1.4-11.7 in the highest exposure group for both sexes combined. There was a RR of 2.2 (95% CI: 1.0-4.7) for ALS in the highest exposure group with the suggestion of an exposure-response relationship. No evidence of increased risk was seen for Parkinson’s disease or multiple sclerosis.
The findings support previous observations of an increased risk of Alzheimer’s disease and ALS among employees occupationally exposed to ELF-MF. Further studies based on morbidity data are warranted.
From the *Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden, †National Institute for Working Life, Solna, Sweden, ‡Department of Occupational and Environmental Health, Stockholm Public Health Center, Stockholm, Sweden, §Division of Occupational Health, Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden, ¶Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark
This work was supported by grant from ELFORSK, Sweden.
Address correspondence to: Niclas Håkansson, Institute of Environmental Medicine, Karolinska Institutet, Box 210, S-171 77 Stockholm, Sweden. Tel: +46 8 728 70 80, Fax: +46 8 30 45 71. E-mail: email@example.com.
Submitted 12 March 2002; final version accepted 12 November 2002.