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On Electric Blankets and Breast Cancer

Sandler, Dale P.

doi: 10.1097/01.EDE.0000082043.52063.30
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The Long Island Breast Cancer Study Project (LIBCSP) is a series of studies designed to address environmental questions about breast cancer. The centerpiece of this effort is the population-based case-control study, Breast Cancer and the Environment on Long Island, and its sister study, the EMF and Breast Cancer on Long Island Study (EBCLIS). These are important and unusual studies. They were Congressionally mandated in 1993 under Public Law 103-43 as a result of pressure from advocates who were alarmed about perceived higher rates of breast cancer in Long Island, NY, and several other northeastern communities. The concerns of the advocates and Congress enabled the investigators to devote far more attention and resources to possible environmental risk factors than previous studies. These political pressures also constrained the design of the study and, to a lesser extent, the hypotheses to be investigated. Exposures to organochlorine pesticides and EMF became a focus of the Long Island studies.

By the time results became available from the LIBCSP, however, a consensus had already begun to build that these exposures do not make much contribution to the risk of breast cancer. Six large studies since 1998 have found no evidence for a link between electric blankets and breast cancer (see O’Leary et al.1). The most recent and thorough of these was designed specifically to address hypotheses related to a range of EMF exposures, and the authors have reported odds ratios close to 1.0 for a variety of measures of electric blanket use.2

So why have the editors of Epidemiology chosen to publish the electric blanket results from the EBCLIS,1 especially given our recent editorial by Savitz on setting a higher threshold for EMF papers?3 Savitz allowed that the jury was still out on EMF and breast cancer, and that the results of several ongoing studies, including the one reported here, were awaited. Although O’Leary and her colleagues focus their paper on only one aspect of EMF exposure, they do so with exceptional thoroughness, for example, by exploring additional markers of dose and stratifying by characteristics of the woman (menopause status) or the tumor (receptor status) that might relate to proposed hormonal mechanisms of causation.4

Although this paper is not the first to find electric blankets blameless with regard to breast cancer, the editors agree that it merits space in the journal, both because of the high quality of the work and the high level of public concern that motivated the study in the first place. As Neutra cogently argues in his commentary also published in this issue,5 narrow scientific criteria are not the only ones that deserve consideration when assessing epidemiologic research. This study was specifically designed to address the electric blanket question as one of its main hypotheses. It has done so perhaps as well as an epidemiologic design is capable of doing. Its negative findings are clear and consistent with the best previous research. Perhaps this intriguing hypothesis can now be put to rest.


1.Kabat GC, O’Leary ES, Schoenfeld ER, et al. Electric blanket use and breast cancer on Long Island. Epidemiology. 2003;14:314–320.
2.Davis S, Mirik DK, Stevens RG. Residential magnetic fields and the risk of breast cancer. Am J Epidemiol. 2002;155:446–454.
3.Savitz DA. Health effects of electric and magnetic fields: are we done yet? Epidemiology. 2003;14:15–17.
4.Stevens RG, Electric power use and breast cancer. A hypothesis. Am J Epidemiol. 1987;125:556–561.
5.Neutra R. What to research and publish. Epidemiology. 2003;14:310–311.
© 2003 Lippincott Williams & Wilkins, Inc.