Epidemiological study (observational study)

Occupational Exposure to Electric Shocks and Magnetic Fields and Amyotrophic Lateral Sclerosis in Sweden. epidem.

By: Fischer H, Kheifets L, Huss A, Peters TL, Vermeulen R, Ye W, Fang F, Wiebert P, Vergara XP, Feychting M

Published in: Epidemiology 2015; 26 (6): 824-830

Type of risk estimation:

incidence

(odds ratio (OR))

Exposure

- 50/60 Hz
- magnetic field
- (contact) current
- high volt./current device/welder
- electric injuries/electrocution
- occupational

Assessment

job exposure matrix

Exposure groups

Reference group 1	magnetic field exposure: low
Group 2	magnetic field exposure: medium
Group 3	magnetic field exposure: high
Reference group 4	risk for electrical shocks: low
Group 5	risk for electrical shocks: medium
Group 6	risk for electrical shocks: high
Reference group 7	no electric occupations
Group 8	electric occupations including welders
Group 9	welders

Population

Group:
- men
- women
Age: ≥ 20 years
Observation period: 1991 - 2010
Study location: Sweden

Case group

Characteristics: patients with amyotrophic lateral sclerosis
Data source: Swedish Patient Register, Migration Register and Cause of Death Register

Control group

living in Sweden
Selection:
- population-based
Matching:
- sex
- birth year
- case:control = 1:5

Study size

	Cases	Controls
Eligible	5,020	25,100
Evaluable	4,709	23,335

Statistical analysis method:

conditional logistic regression

( adjustment:

residential area
socioeconomic status
education

)

Conclusion (acc. to author)

Overall, no associations between occupational exposure to magnetic fields or electric shocks and the incidence of amyotrophic lateral sclerosis were observed. For individuals less than 65 years old, an increased risk was found with high electric shock exposure (OR 1.22, CI 1.03-1.43), however, not in the age group 65 years or older (OR 0.92, CI 0.81-1.05). Results were similar regardless which job exposure matrices, exposure definitions or cutpoints were used. No increased risk was found for electric occupations (including welders). For welders, no association was observed overall, although for welders less than 65 years an increased risk was observed (OR 1.52, CI 1.05-2.21). There was no evidence that electric shock was a confounder in the analyses of magnetic fields.
The authors concluded that previous observations of higher risk of amyotrophic lateral sclerosis in electrical occupations were not confirmed in this study and only weak support for associations between electric shocks and amyotrophic lateral sclerosis was provided.

Study funded by

Karolinska Institute, Sweden
Swedish Research Council (VR)
Centers for Disease Control and Prevention (CDC), USA
National Institute for Occupational Safety and Health (NIOSH), USA
Southern California NIOSH Education and Research Center, USA
Swedish Research Council for Health, Working Life and Welfare (Forte), Sweden

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