Clinical Brief

With Comments from Russell H. Greenfield, MD

Electric Blankets and Breast Cancer

Source: Kabat GC, et al. Electric blanket use and breast cancer on Long Island. Epidemiology 2003;14:514-520.

Goal: To evaluate the relationship between exposure to low-frequency electromagnetic fields (EMFs) and breast cancer risk.

Design: Population-based, case-control study performed in two stages—Part I was the Long Island Breast Cancer Study Project (LIBCSP), which focused primarily on exposure to organochlorines and other environmental pollutants; Part II, the Electromagnetic Fields and Breast Cancer on Long Island Study (EBCLIS), included a subset of LIBCSP participants.

Subjects: Women with first breast cancer diagnosed between August 1996 and July 1997 and matched controls were eligible for entry into LIBCSP. Women who were younger than age 75 and had lived in their current homes for more than 15 years were eligible to participate in EBCLIS (responses from 576/663, 87%, and 585/702, 83%, of available cases and controls, respectively).

Methods: During the LIBCSP, women were asked to participate in a two-hour comprehensive questionnaire and to provide blood and urine specimens. Participants in EBCLIS took part in a 30-minute interview administered at their homes that focused on use of electric blankets, exposure to other appliances, and potential occupational EMF exposure. EMF measurements were determined in two rooms of the home as well as at the front door. Later, electrical wiring configuration was diagramed from outside the home. Some analyses were stratified according to menopausal status.

Results: Analyses of both the LIBCSP and EBCLIS groups showed no association between breast cancer and electric blanket use, frequency of use, duration of use, or other indicators of intense exposure to EMF.

Conclusion: Results of this study do not support an association between use of electric blankets and an increased risk of breast cancer.

Study strengths: Thorough nature of inquiry into possible EMF exposure from electric blankets; sample size (albeit less than was targeted).

Study weaknesses: Inherent limitations of self-reported use of electric blankets; low rate of control participation during LIBCSP, especially among older women; seasonality not addressed.

Of note: Eight prior studies of electric blanket use and breast cancer risk showed either no association or a slight association with continuous use throughout the night; electric blankets purchased before 1989 produce stronger EMF than those purchased at later dates; analysis of household and occupational appliance use in EBCLIS participants has yet to be reported.

We knew that: It has been posited that low-frequency EMF may inhibit the normal nocturnal rise in melatonin, thereby leading to increased estrogen levels and greater risk for development of breast cancer (especially in premenopausal women).

Clinical import: Long Island is one of a few locales that exhibits a high breast cancer rate relative to the rest of the country. For years researchers have been trying to identify environmental factors that might explain the apparent regional disparity in breast cancer risk, including exposure to EMFs. Although prevalence of electric blanket use among today’s women is unlikely to be very high, it is conceivably a source of significant exposure to EMFs because the blanket often is applied directly to the body. This study provides welcome respite in that it appears that electric blanket use, in and of itself, does not cause breast cancer.

What to do with this article: Keep a hard copy in your file cabinet.

Dr. Greenfield, Medical Director, Carolinas Integrative Health, Carolinas HealthCare System, Charlotte, NC, is Executive Editor of Alternative Medicine Alert.