Electric blanket use and breast cancer in the Nurses' Health Study

Electric and magnetic fields (EMFs) have been hypothesized to increase the risk of breast cancer, and electric blankets represent an important source of exposure to EMFs. The authors examined the relation between electric bla nket use and invasive breast cancer in the Nurses' Health Study. On the bie nnial questionnaire in 1992, 87,497 women provided information on this expo sure during three consecutive time periods. In a prospective analysis with 301,775 person-years of follow-up through 1996 (954 cases), the relative ri sk for any electric blanket use was not elevated (relative risk (RR) = 1.08 , 95% confidence interval (CI): 0.95, 1.24) after controlling for breast ca ncer risk factors. There was a weak association between breast cancer and e lectric blanket use at least 16 years before diagnosis and long-term use in age-adjusted analyses but not in multivariate models. In a retrospective a nalysis of 1,318,683 person-years of follow-up (2,426 cases), the multivari ate relative risk associated with use before disease follow-up began was nu ll (RR = 1.05, 95% CI: 0.95, 1.16). Similar results were obtained in analys es stratified by menopause and restricted to estrogen receptor-positive bre ast cancers. While 95% confidence intervals for these estimates did not exc lude small risks, overall, results did not support an association between b reast cancer risk and exposure to EMFs from electric blankets.