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British Journal of Cancer (2010) 103, 1128–1135. doi:10.1038/sj.bjc.6605838
Pooled analysis of recent studies on magnetic fields and childhood leukaemia
L Kheifets1, A Ahlbom2, C M Crespi3, G Draper4, J Hagihara5, R M Lowenthal6, G Mezei7, S Oksuzyan1, J Schüz8, J Swanson9, A Tittarelli10, M Vinceti11 and V Wunsch Filho12
1Department of Epidemiology, UCLA School of Public Health, 650 Charles Young Drive, Los Angeles, CA 90095, USA
2Division of Epidemiology, Institute of Environmental Medicine, Nobels väg 13, Karolinska Institutet, Stockholm SE-171 77, Sweden
3Department of Biostatistics, UCLA School of Public Health, Charles Young Drive, Los Angeles, CA 90095, USA
4Childhood Cancer Research Group, University of Oxford, Richards Building, Old Road Campus, Oxford OX3 7LG, UK
5Miyagi University, 1-1 Gakuen, Taiwa-cho Kurokawa-gun, Miyagi 981-3298, Japan
6School of Medicine and Menzies Research Institute, University of Tasmania, 17 Liverpool Street, Hobart, Tasmania 7000, Australia
7Environment Department, Electric Power Research Institute, 3420 Hillview Avenue, Palo Alto, CA 94304, USA
8Institute of Cancer Epidemiology, Danish Cancer Society, Strandboulevarden 49, Copenhagen DK-2100, Denmark
9National Grid, plc, 1-3 Strand, London WC2N 5EH, UK
10Cancer Registry and Environmental Epidemiology Unit, National Cancer Institute, Via Venezian, Milan 120133, Italy
11Department of Public Health Sciences, University of Modena and Reggio Emilia, Via Campi 287, Modena 41100, Italy
12School of Public Health, Av. Dr Arnaldo, 715, Universidade de São Paulo, 01246-904 São Paulo, Brazil
Correspondence: Dr L Kheifets, E-mail: kheifets@ucla.edu
Received 17 March 2010; Revised 9 June 2010; Accepted 12 July 2010.
Background: Previous pooled analyses have reported an association between magnetic fields and childhood leukaemia. We present a pooled analysis based on primary data from studies on residential magnetic fields and childhood leukaemia published after 2000.
Methods: Seven studies with a total of 10,865 cases and 12,853 controls were included. The main analysis focused on 24-h magnetic field measurements or calculated fields in residences.
Results: In the combined results, risk increased with increase in exposure, but the estimates were imprecise. The odds ratios for exposure categories of 0.1–0.2 μT, 0.2–0.3 μT and 0.3 μT, compared with <0.1 μT, were 1.07 (95% CI 0.81–1.41), 1.16 (0.69–1.93) and 1.44 (0.88–2.36), respectively. Without the most influential study from Brazil, the odds ratios increased somewhat. An increasing trend was also suggested by a nonparametric analysis conducted using a generalised additive model.
Conclusions: Our results are in line with previous pooled analyses showing an association between magnetic fields and childhood leukaemia. Overall, the association is weaker in the most recently conducted studies, but these studies are small and lack methodological improvements needed to resolve the apparent association. We conclude that recent studies on magnetic fields and childhood leukaemia do not alter the previous assessment that magnetic fields are possibly carcinogenic.
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