Risk of premenopausal breast cancer and use of electric blankets.

Electric blanket use, estimated to significantly increase background exposure to 60-Hz electromagnetic fields, has been hypothesized to increase breast cancer risk. From 1986 to 1991 in western New York State, the authors investigated the use of electric blankets as a risk factor for breast cancer in a case-control study of premenopausal women. A total of 290 premenopausal breast cancer cases and 289 age-matched randomly selected community controls were queried in regard to their use of electric blankets in the previous 10 years, including frequency of use in season and mode of use. After adjusting for age, education, and other risk factors, the odds ratio for use of an electric blanket at any time in the previous 10 years (40% of cases and 37% of controls) was 1.18 (95% confidence interval (CI) 0.83-1.68). Estimates of risk did not differ in a dose-response fashion for number of years of electric blanket use. The risk associated with daily use in season relative to nonuse was 1.27 (95% CI 0.86-1.88). The risk of breast cancer among those who reported use of the blanket through the night was 1.43 (95% CI 0.94-2.17). However, the risk for those who reported daily use in season, continuously throughout the night for the previous 10 years was 1.10 (95% CI 0.59-2.05). These findings do not support the hypothesis that electric blanket use is associated with an increased risk for breast cancer. Studies with improved measures of more highly exposed individuals with quantification of total electromagnetic field exposure might clarify the uncertainties regarding risk of breast cancer associated with such exposure.