American Journal of Epidemiology Advance Access originally published online on May 7, 2007
American Journal of Epidemiology 2007 166(3):263-269; doi:10.1093/aje/kwm080
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ORIGINAL CONTRIBUTIONS |
Nighttime Exposure to Electromagnetic Fields and Childhood Leukemia: An Extended Pooled Analysis
1 Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark
2 Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD
3 British Columbia Cancer Agency, Vancouver, British Columbia, Canada
4 Epidemiology and Genetics Unit, Department of Health Sciences, University of York, York, United Kingdom
5 Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden
6 Department of Epidemiology, School of Public Health, University of California, Los Angeles, Los Angeles, CA
7 Electric Power Research Institute, Palo Alto, CA
Correspondence to Dr. Joachim Schüz, Institute of Cancer Epidemiology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen, Denmark (e-mail: joachim{at}cancer.dk).
Received for publication November 10, 2006. Accepted for publication February 7, 2007.
It has been hypothesized that nighttime bedroom measurements of extremely low frequency electromagnetic fields (ELF EMF) may represent a more accurate reflection of exposure and have greater biologic relevance than previously used 24-/48-hour measurements. Accordingly, the authors extended a pooled analysis of case-control studies on ELF EMF exposure and risk of childhood leukemia to examine nighttime residential exposures. Data from four countries (Canada, Germany, the United Kingdom, and the United States) were included in the analysis, comprising 1,842 children diagnosed with leukemia and 3,099 controls (diagnosis dates ranged from 1988 to 1996). The odds ratios for nighttime ELF EMF exposure for categories of 0.1–<0.2 µT, 0.2–<0.4 µT, and 
0.4 µT as compared with <0.1 µT were 1.11 (95% confidence interval (CI): 0.91, 1.36), 1.37 (95% CI: 0.99, 1.90), and 1.93 (95% CI: 1.11, 3.35), respectively. The fact that these estimates were similar to those derived using 24-/48-hour geometric mean values (odds ratios of 1.09, 1.20, and 1.98, respectively) indicates that the nighttime component cannot, on its own, account for the pattern observed. These results do not support the hypotheses that nighttime measures are more appropriate; hence, the observed association between ELF EMF and childhood leukemia still lacks a plausible explanation.
child; electromagnetic fields; epidemiologic methods; leukemia, lymphocytic, acute, L1; melatonin; meta-analysis; neoplasms
Abbreviations: CI, confidence interval; ELF EMF, extremely low frequency electromagnetic fields
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