Epidemiological study (observational study)

Extremely low-frequency magnetic field exposure, electrical shocks and risk of Parkinson's disease epidem.

By: van der Mark M, Vermeulen R, Nijssen PC, Mulleners WM, Sas AM, van Laar T, Kromhout H, Huss A

Published in: Int Arch Occup Environ Health 2015; 88 (2): 227-234

Aim of study (acc. to author)

A case-control study was conducted in the Netherlands to investigate the possible association between the risk of Parkinson disease and exposure to extremely low-frequency magnetic field and to electrical shocks from both occupational and non-occupational sources.

Endpoint/type of risk estimation

neurodegenerative diseases: Parkinson disease

Type of risk estimation:

incidence

(odds ratio (OR))

Exposure

- electric injuries/electrocution
- occupational
- personal

Assessment

questionnaire: each job in the occupational history (number of years, job title, type of industry, company name and main tasks); use of several household appliances at current age and at the age of 20, 40 and 60 (hairdryer, electrical shaver, electrical alarm clock, water bed and electrical blanket); non-work related electrical welding (number of years, average number of days per year and average welding duration); estimated lifetime number of experienced electrical shocks
job exposure matrix
calculation: cumulative job exposure was calculated summing exposure of all years in the job history using weights (0 for low, 1 for medium and 4 for high exposure); cumulative exposure to household appliances was calculated from reported years of use of several electrical appliances and assumptions about exposure intensity, frequency and duration of use

Exposure groups

Group	Description
Reference group 1	job exposure matrix: only low
Group 2	job exposure matrix, ever exposure: medium
Group 3	job exposure matrix, ever exposure: high
Group 4	exposure duration: 1 - 8 years
Group 5	exposure duration: 9 - 23 years
Group 6	exposure duration: 24 - 55 years
Group 7	cumulative exposure: 1 - 9 unit-years
Group 8	cumulative exposure: 10 - 26 unit-years
Group 9	cumulative exposure: 27 - 188 unit-years
Reference group 10	household appliances exposure + non -occupational welding: 0 µT-years
Group 11	household appliances exposure + non -occupational welding: > 0 - 2.0 µT-years
Group 12	household appliances exposure + non -occupational welding: > 2.0 - 3.8 µT-years
Group 13	household appliances exposure + non -occupational welding: > 3.8 - 5.7 µT-years
Group 14	household appliances exposure + non -occupational welding: > 5.7 µT-years

Population

Group:
- men
- women
Age: 34–91 years
Observation period: April 2010 - June 2012
Study location: The Netherlands

Case group

Characteristics: patients with a first diagnosis of Parkinson disease between January 2006 and December 2011
Data source: 5 hospitals in Tilburg, Nijmegen, Groningen and Schiedam

Control group

individuals who attended the same departments of neurology within the same specified time frame with diagnosis of median nerve neuropathy, ulnar nerve neuropathy, thoracic and lumbar disk disease, or sciatica
Selection:
- hospital-based
Matching:
- sex
- age
- hospital visiting date
- case:control = 1:2

Study size

	Cases	Controls
Eligible	1,001	-
Contacted	993	-
Participants	448	876
Participation rate	45 %	35 %

Statistical analysis method:

conditional logistic regression

(adjustment:

education
smoking, coffee consumption, collar worker category

)

Results (acc. to author)

No association between the risk of Parkinson disease and exposure to extremely low-frequency magnetic field and to electrical shocks from both occupational and non-occupational sources was found. However, a quite consistently reduced risk estimates across the majority of the exposure categories explored was observed. Given the results of the previous studies and the absence of any postulated mechanism, this is unlikely to represent a true protective effect of extremely low-frequency magnetic fields or electrical shocks on the occurrence of Parkinson disease.
The authors conclude that the results of the present study suggest that no association exists between Parkinson disease and exposure to extremely low-frequency magnetic fields, electrical shocks or having worked in 'electrical occupations'.

Study funded by

Stichting Parkinson Fonds, The Netherlands
ZonMw, The Netherlands

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