Epidemiological study (observational study)

Power-frequency magnetic fields and childhood brain tumors: a case-control study in Japan epidem.

By: Saito T, Nitta H, Kubo O, Yamamoto S, Yamaguchi N, Akiba S, Honda Y, Hagihara J, Isaka K, Ojima T, Nakamura Y, Mizoue T, Ito S, Eboshida A, Yamazaki S, Sokejima S, Kurokawa Y, Kabuto M

Published in: J Epidemiol 2010; 20 (1): 54-61

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Aim of study (acc. to author)

A case-control study was conducted in Japan to investigate the association between exposure to power-frequency magnetic fields and childhood brain tumors.

Endpoint/type of risk estimation

childhood brain/CNS tumor

Type of risk estimation:

incidence

(odds ratio (OR))

Exposure

Assessment

questionnaire: mother's and child's use of electric appliances
measurement: 1-week-long continuous measurement at 30-sec intervals in the child's bedroom and 5-min-long spot measurement at several points inside and outside the house
calculation: distance from residence to nearest high voltage power line based on maps provided by the power companies and geographical information system sofware

Exposure groups

Group	Description
Reference group 1	bedroom magnetic field level: below 0.1 µT
Group 2	bedroom magnetic field level: 0.1-0.2 µT
Group 3	bedroom magnetic field level: 0.2-0.4 µT
Group 4	bedroom magnetic field level: above 0.4 µT

Population

Group:
- children
Age: 0–14 years
Observation period: May 1999 - September 2002
Study location: Japan (Tokyo, Nagoya, Kyoto, Osaka and Kitakyushu metropolitan areas)

Case group

Characteristics: brain tumor, histopathologically confirmed
Data source: network of 107 hopsitals throughout Japan

Control group

Selection:
- population-based
Matching:
- sex
- age
- area
- population size of the municipality D: Größ

Study size

	Cases	Controls
Eligible	167	-
Participants	72	189
Evaluable	55	99

Statistical analysis method:

conditional logistic regression

(adjustment:

mother's education level

)

Results (acc. to author)

The risk of brain tumor was significantly higher among children whose bedroom magnetic field level was greater than 0.4 µT (OR 10.9, CI 1.05-113). A not statistically significant increased risk was observed for children whose bedroom magnetic field level was in the range of 0.2 to 0.4 µT (OR 1.58, CI 0.25-9.83).
The authors concluded that a positive association was found between exposure to magnetic fields above 0.4 µT and the risk of childhood brain tumors. This association could not be explained solely by confounding factors or selection bias.

Limitations (acc. to author)

The findings are based on low numbers.

Study funded by

Ministry of Education, Culture, Sports, Science and Technology, Japan

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