Letter

Childhood cancer and power lines: Results depend on chosen control group

BMJ 2005; 331 doi: 10.1136/bmj.331.7517.635 (Published 15 September 2005)
Cite this as: BMJ 2005;331:635.1

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  1. Leeka Kheifets, professor of epidemiology (kheifets@ucla.edu),
  2. Maria Feychting, associate professor,
  3. Joachim Schüz, head
  1. UCLA School of Public Health, Department of Epidemiology, 73-284 CHS, 650 Charles E Young Drive South, Los Angeles, CA 90095-1772, USA
  2. Institute of Environmental Medicine, Karolinska Institutet, Box 210, S-17177 Sweden
  3. Department of Biostatistics and Epidemiology, Institute of Cancer Epidemiology, DK-2100 Copenhagen, Denmark

    Editor—Given the large size of the study by Draper et al,1 the risk estimates should be stable. Furthermore, because contact with the subject was not necessary, selection bias due to the differential participation among cases and controls as in previous studies has been avoided.2

    We were therefore surprised by the dependence of the results on the chosen control group noted by the authors (who used the central nervous system and other cancer controls for leukaemia cases in …

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