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Epidemiological study (observational study)

Occupational exposure and amyotrophic lateral sclerosis in a prospective cohort.

Published in: Occup Environ Med 2017

Aim of study (acc. to author)

The association between the occupational exposure to extremely low-frequency magnetic fields, electrical shocks as well as other risk factors and amyotrophic lateral sclerosis mortality was investigated in the Netherlands Cohort Study. Furthermore, the effects of combined exposure to these occupational risk factors were studied.

Further details

Following a case-cohort approach, a randomly subcohort including 2411 men and 2589 women was drawn.

Endpoint/type of risk estimation

Type of risk estimation:
  • mortality
(hazard ratio)

Exposure

Assessment

Exposure groups

Reference group 1 magnetic field exposure: background
Group 2 magnetic field exposure: low
Group 3 magnetic field exposure: high
Reference group 4 cumulative exposure: background
Group 5 cumulative exposure: 1st terzile
Group 6 cumulative exposure: 2nd terzile
Group 7 cumulative exposure: 3rd terzile
Reference group 8 electric shock risk: background
Group 9 electric shock risk: low
Group 10 electric shock risk: high

Population

  • Group:
    • men
    • women
  • Age: ≥ 55 years
  • Characteristics: participants of the Netherlands Cohort Study (NLCS) on diet and cancer
  • Observation period: 1986 - 2003
  • Study location: Netherlands
  • Data source: Dutch Bureau of Genealogy, municipal resident registration, Statistics Netherlands

Study size

Total 120,852
Other: 17.3 years of follow-up
Statistical analysis method:
  • Cox proportional regressions analysis
( adjustment: )

Conclusion (acc. to author)

In total, 88 male and 70 female ALS deaths (0.15% and 0.11% of entire cohort, respectively) were registered.
A statistically significant association between occupational exposure to extremely low-frequency magnetic fields and to amyotrophic lateral sclerosis mortality in men was observed: the hazard ratio for ever holding a job with high exposure (group 3) versus background (group 1) was 2.19 (CI 1.02-4.73) and the hazard ratio for the highest tertile of cumulative exposure (group 7) versus background (group 4) was 1.93 (CI 1.05-3.55). No increased risk was found for other occupational exposures such as electrical shock, solvents, metals or pesticides.
The authors conclude that the results offer further support for an association between exposure to extremely low-frequency magnetic fields and amyotrophic lateral sclerosis.

Study funded by

  • ZonMw, The Netherlands

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