Study type: Epidemiological study

Occupational Exposure to Electric Shocks and Extremely Low-Frequency Magnetic Fields and Motor Neurone Disease. epidem.

Published in: Am J Epidemiol 2020: kwaa214 [in press]

Aim of study (acc. to author)

A case-control study was conducted in New Zealand to investigate the associations between occupational exposure to electric shocks, extremely low-frequency magnetic fields (ELF-MF) and motor neurone disease.

Endpoint/type of risk estimation

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

Exposure

Assessment

Exposure groups

Group Description
Reference group 1 electric shocks: never exposed above background level
Group 2 electric shocks: ever exposed above background level
Reference group 3 electric shocks: background level
Group 4 electric shocks: medium exposure only
Group 5 electric shocks: ever high exposure
Reference group 6 electric shocks: duration of exposure, background level
Group 7 electric shocks: duration of exposure < 3 years
Group 8 electric shocks: duration of exposure 3 - 8 years
Group 9 electric shocks: duration of exposure 9 - 24 years
Group 10 electric shocks: duration of exposure > 24 years
Reference group 11 electric shocks: cumulative exposure, background
Group 12 electric shocks: cumulative exposure 4 unit-years
Group 13 electric shocks: cumulative exposure 4 - 16 unit-years
Group 14 electric shocks: cumulative exposure 17 - 52 unit-years
Group 15 electric shocks: cumulative exposure > 52 unit-years
Reference group 16 extremely low frequency magnetic fields: never exposed above background level
Group 17 extremely low frequency magnetic fields: ever exposed above background level
Reference group 18 extremely low frequency magnetic fields: background level
Group 19 extremely low frequency magnetic fields: medium exposure only
Group 20 extremely low frequency magnetic fields: ever high exposure
Reference group 21 extremely low frequency magnetic fields: duration of exposure, background level
Group 22 extremely low frequency magnetic fields: duration of exposure < 3 years
Group 23 extremely low frequency magnetic fields: duration of exposure 3 - 8 years
Group 24 extremely low frequency magnetic fields: duration of exposure 9 - 23 years
Group 25 extremely low frequency magnetic fields: duration of exposure > 23 years
Reference group 26 extremely low frequency magnetic fields: cumulative exposure, background level
Group 27 extremely low frequency magnetic fields: cumulative exposure < 4 unit-years
Group 28 extremely low frequency magnetic fields: cumulative exposure 4 - 12 unit-years
Group 29 extremely low frequency magnetic fields: cumulative exposure 13 - 28 unit-years
Group 30 extremely low frequency magnetic fields: cumulative exposure > 28 Einheiten-Jahre

Population

Case group

Control group

Study size

Cases Controls
Participants 321 605
Participation rate 92 % 48 %
Evaluable 319 604
Statistical analysis method: (adjustment: )

Conclusion (acc. to author)

An elevated risk for motor neuron disease was observed for having ever worked in a job with potential for electric shocks (group 2: OR 1.35, CI 0.98-1.86), with the strongest association for the highest level of exposure (group 5: OR 2.01, CI 1.31-3.09). Analysis by duration of exposure suggested a non-linear association: risk was increased for both short-duration (<3 years) (OR 4.69, CI 2.25-9.77) and long-duration in a job with high level of electric shock exposure (>24 years; OR 1.88, CI 1.05-3.36), with less pronounced associations for intermediate durations.
No association between exposure to extremely low frequency magnetic fields and motor neuron disease was found.
The authors conclude that their findings provide support for an association between occupational exposure to electric shocks and motor neurone disease but did not show associations with exposure to work-related extremely low frequency magnetic fields.

Study funded by

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