Résumé :
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[BDSP. Notice produite par INIST b3R0xDX7. Diffusion soumise à autorisation]. Menstrual cycle characteristics and ovulatory infertility were evaluated in relation to breast cancer risk among 116,678 women in the Nurses'Health Study II, a prospective cohort study of female registered nurses who were aged 25-42 years and living in 14 US states at enrollment in 1989. During 396,299 person-years of follow-up between return of the baseline questionnaire and June 1993,251 cases of breast cancer were identified in this cohort. The multivariate relative risk (RR) associated with age at menarche>13 years compared with age 39 days or too irregular for estimation of a usual cycle length, 0.41 (0.18-0.94). The multivariate relative risk associated with a history of ovulatory infertility, compared with no such history, was 0.41 (95% Cl 0.180.93). These results are consistent with the hypothesis that reduced exposure to ovulatory menstrual cycles provides a protective effect against breast cancer.
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