The cohort of the Nurses' Health Study comprises 121,700 U.S. female registered nurses who were 30 to 55 years of age in 1976. The study was originally designed to assess risk factors for cancer and cardiovascular outcomes, with particular emphasis on the potential effects of oral contraceptives, hormones, cigarette smoking, and hair dyes. In 1980 a large dietary component was added to the study and has shifted the emphasis to include diet and micronutrient risk factors and other life-style factors, and an expanded list of disease outcomes. The participants are followed up every 2 years with a mailed questionnaire that updates exposure information (e.g., partity, use of oral contraceptives, weight, cigarette smoking) and also allows the women to report major illnesses that have been diagnosed since the last questionnaire. During the first 10 years of follow-up we have observed no relation between past use of oral contraceptives and risk of breast cancer and no risk associated with use before a first pregnancy. However, we have found a significant increase in risk for breast cancer among current users of oral contraceptives (relative risk [RR] = 1.53 compared with nonusers). We have observed no relation between cigarette smoking and risk of breast cancer.

Original languageEnglish
Pages (from-to)135-140
Number of pages6
JournalCurrent Problems in Obstetrics, Gynecology and Fertility
Issue number4
StatePublished - Jan 1 1990


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