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Incidence of breast cancer in a Norwegian cohort of women with potential workplace exposure to 50 Hz magnetic fields
Author(s) -
Kliukiene Jolanta,
Tynes Tore,
Martinsen Jan I.,
Blaasaas Karl G.,
Andersen Aage
Publication year - 1999
Publication title -
american journal of industrial medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.7
H-Index - 104
eISSN - 1097-0274
pISSN - 0271-3586
DOI - 10.1002/(sici)1097-0274(199907)36:1<147::aid-ajim21>3.0.co;2-x
Subject(s) - medicine , poisson regression , confidence interval , breast cancer , demography , cohort , cohort study , relative risk , cancer registry , incidence (geometry) , norwegian , population , epidemiology , cancer , environmental health , linguistics , philosophy , physics , sociology , optics
Background The risk of breast cancer was investigated in a large dynamic population‐based cohort of all 1.1 million economically active women in Norway with potential exposure to 50 Hz magnetic fields at the censuses of 1960, 1970, and 1980. Methods The follow‐up period for the cohort was 1961–1992. For each woman, date of birth and census information on occupation and socioeconomic status were ascertained. These data were linked to the breast cancer morbidity information in the Cancer Registry of Norway. Exposure to magnetic fields was assessed a priori using two different approaches. In the first approach, hours per week in a potential magnetic field above background level (0.1 μT) were classified by an expert panel. In the second approach, measured magnetic fields from a separate study of men at work were allocated to the women's census job titles. In both approaches, exposure was cumulated over the years of employment (work hours and μT ‐years, respectively). Results The Poisson regression analysis showed a risk ratio (RR) of 1.14 (95% confidence interval (CI) = 1.10–1.19) in the highest exposure category compared to the lowest when using the first approach, and the corresponding RR was 1.08 (95% CI = 1.01–1.16) when using the second approach. For women younger than 50 years, RR was 1.20 (95% CI = 1.11–1.29) and 1.12 (95% CI = 0.98–1.28), respectively. Conclusions The results give some support to the hypothesis that exposure to 50 Hz magnetic fields may increase the risk of breast cancer. However, since no direct information on exposure was available, no firm conclusions can be drawn. Am. J. Ind. Med. 36:147–154, 1999. © 1999 Wiley‐Liss, Inc.