Epidemiological study (observational study)

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

By: Huss A, Spoerri A, Egger M, Kromhout H, Vermeulen R

Published in: Amyotroph Lateral Scler Frontotemporal Degener 2015; 16 (1-2): 80-85

Aim of study (acc. to author)

The association between occupational exposure to magnetic fields and electric shocks and mortality of amyotrophic lateral sclerosis was investigated in the Swiss National Cohort.

Further details

Occupational exposure was assessed by applying job exposure matrices for occupations at censuses 1990 and 2000. Furthermore, the job titles were classified into electrical occupations according to Deapen et al. (1988) und Feychting et al. (2013).

Endpoint/type of risk estimation

neurodegenerative diseases: amyotrophic lateral sclerosis

Type of risk estimation:

mortality

(hazard ratio)

Exposure

- electric injuries/electrocution
- occupational

Assessment

list: classification of job titles into electrical occupations
job exposure matrix: data on occupations at censuses 1990 and 2000

Exposure groups

Group	Description
Reference group 1	magnetic field exposure (job-exposure matrix): low
Group 2	magnetic field exposure (job-exposure matrix): medium
Group 3	magnetic field exposure (job-exposure matrix): high
Reference group 4	electrical shocks (job-exposure matrix): low
Group 5	electrical shocks (job-exposure matrix): medium
Group 6	electrical shocks (job-exposure matrix): high
Reference group 7	electrical occupations (according to Deapen et al., 1988): no
Group 8	electrical occupations (according to Deapen et al., 1988): yes
Reference group 9	electrical occupations (according to Feychting et al., 2003): no
Group 10	electrical occupations (according to Feychting et al., 2003): yes

Population

Group:
- men
- women
Age: ≥ 30 years
Characteristics: participants of the Swiss National Cohort
Observation period: 1990 - 2008
Study location: Switzerland
Data source: death registry, Swiss National Cohort
Exclusion criteria: pensioners

Study size

Type	Value
Total	2,167,046

Statistical analysis method:

Cox proportional regressions analysis

(adjustment:

sex
nationality

)

Results (acc. to author)

A total of 278 persons of the study population died from amyotrophic lateral sclerosis.
When analyzed separately for each census data, mortality from amyotrophic lateral sclerosis was not increased for workers exposed to extremely low frequency magnetic fields, for workers at risk of electrical shocks, or employed in electrical occupations in either 1990 or 2000. Mortality was higher in workers who had medium or high magnetic field exposure in both censuses (HR 1.55, CI 1.11-2.15), but closer to unity for electrical shocks (HR 1.17, CI 0.83-1.65). When both exposures were included in the same model, the hazard ratio for extremely low frequency magnetic fields changed little (HR 1.56, CI 1.09-2.25), but the hazard ratio for electric shocks was attenuated to 0.97 (CI 0.66-1.42).
The authors concluded that there was an association between exposure to extremely low frequency magnetic fields and mortality from amyotrophic lateral sclerosis among workers with a higher likelihood of long-term exposure.

Study funded by

Swiss National Science Foundation (SNF)
ZonMw, The Netherlands

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