Study type: Epidemiological study (observational study)

Case-control study of occupational exposure to electric shocks and magnetic fields and mortality from amyotrophic lateral sclerosis in the US, 1991-1999. epidem.

Published in: J Expo Sci Environ Epidemiol 2015; 25 (1): 65-71

Aim of study (acc. to author)

A case-control study was conducted in the USA to investigate the association between occupational exposure to electric shocks and magnetic fields and mortality from amyotrophic lateral sclerosis.

Endpoint/type of risk estimation

Type of risk estimation: (odds ratio (OR))

Exposure

Assessment

Exposure groups

Group Description
Reference group 1 non-electric occupations
Group 2 electric occupations
Group 3 electric occupations, not high electric shocks
Group 4 electric occupations, high electric shocks
Group 5 electric occupations, not high magnetic fields (< 0.3µmT)
Group 6 electric occupations, high magnetic fields (≥ 0.3µmT)
Reference group 7 non-welding occupations
Group 8 welding occupations
Group 9 welding occupations, not high electric shocks
Group 10 welding occupations, high electric shocks
Group 11 welding occupations, not high magnetic fields (< 0.3µmT)
Group 12 welding occupations, high magnetic fields (≥ 0.3µmT)
Reference group 13 electric shocks: low
Group 14 electric shocks: medium
Group 15 electric shocks: high
Reference group 16 magnetic field exposure: low
Group 17 magnetic field exposure: medium
Group 18 magnetic field exposure: high

Population

Case group

Control group

Study size

Cases Controls
Evaluable 5,886 57,667
Statistical analysis method: (adjustment: )

Conclusion (acc. to author)

A moderately increased mortality from amyotrophic lateral sclerosis was observed for those who worked within electric occupations (OR 1.23, CI 1.04-1.47). Exposure to electric shocks was inversely associated with mortality from amyotrophic lateral sclerosis: workers with high exposure (OR 0.73, CI 0.67-0.79) had a lower risk than workers with medium exposure (OR 0.90, CI 0.84-0.97). No consistent association between occupational magnetic field exposure and mortality from amyotrophic lateral sclerosis was found (high exposure: OR 1.09, CI 1.00-1.19; medium exposure: OR 1.09, CI 0.96-1.23). Exposure to electric shock or magnetic field exposure did not account for the association observed for electric occupations.
A decreased risk between welding occupations and mortality from amyotrophic lateral sclerosis was observed (OR 0.77, CI 0.55-0.89). Among welding occupations, an association similar in magnitude was observed for high and low electric shocks and magnetic field exposure as well as with adjustment for electric shocks, magnetic fields or both.
The authors concluded that an association between electric occupations and mortality from amyotrophic lateral sclerosis was observed which is consistent with previous publications. In the present study, neither electric shocks nor exposure to magnetic fields explained the association between electric occupations and amyotrophic lateral sclerosis.

Study funded by

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