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Epidemiological study (observational study)

Mortality from neurodegenerative disease and exposure to extremely low-frequency magnetic fields: 31 years of observations on Swiss railway employees.

Published in: Neuroepidemiology 2007; 28 (4): 197-206

Aim of study (acc. to author)

The relationship between extremely low-frequency magnetic field (ELF-MF) exposure and mortality from several neurodegenerative conditions in Swiss railway employees was investigated in a cohort study.

Endpoint/type of risk estimation

Type of risk estimation:
  • mortality

Exposure

Assessment

  • measurement: measurements in 1993-1994 and in 2003-2004
  • calculation: annual exposure for each occupational group and cumulative exposure by adding up annual workplace specific exposures according to start and end date of employment based on measurements and modelling

Exposure groups

Group 1 train drivers
Group 2 shunting yard engineers
Group 3 train attendants
Group 4 station masters

Population

  • Group:
    • men
  • Characteristics: men who were registered as employed or retired in the personnel and pension records of the Swiss Federal Railways
  • Observation period: 1972 - 2002
  • Study location: Switzerland

Study size

Total 20,141
Other: 464129 person-years
Statistical analysis method:
  • Cox proportional regressions analysis

Conclusion (acc. to author)

The four occupational groups had considerably different exposures to magnetic fields: the annual average exposure was approximately 21 µT for train drivers, for shunting yard engineers 3.6 µT in 1940, increasing to 6.0 µT in 2000, for train attendants below 2 µT up to 1980, increasing to 4.2 µT in 2000, for station masters increasing from 0.3 in 1940 to 1.0 µT in 2000.
The hazard ratio for train drivers compared to station masters was 1.96 (CI 0.98-3.92) for senile dementia and 3.15 (CI 0.90-11.04) for Alzheimer disease. For every 10 µT years of cumulative exposure senile dementia mortality increased by 5.7% (CI 1.3-10.4), Alzheimer disease by 9.4% (CI 2.7-16.4) and amyotrophic lateral sclerosis by 2.1% (CI -6.8-11.7). There was no evidence for an increase in mortality from Parkinson disease and multiple sclerosis.
The authors conclude that this study suggests a link between exposure to extremely low frequency magnetic fields and Alzheimer disease and indicates that ELF-MF might act in later stages of the disease process.

Study funded by

  • Federal Office of Public Health (FOPH; Bundesamt für Gesundheit), Switzerland
  • Federal Office of Transport (FOT; Bundesamt für Verkehr), Switzerland

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