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 <=12 years was 0.66 (95% confidence interval (Cl) 0.44-0.99).
Short and long menstrual cycle lengths at ages 18-22 years were associated with reduced risk.
Compared with menstrual cycle length 26-31 days, the multivariate relative risks (95% Cls) for more extreme cycle lengths were :
<26 days, 0.50 (0.25-0.98) ;
32-39 days, 0.81 (0.51-1.28) ;
and>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.
Mots-clés Pascal : Tumeur maligne, Glande mammaire, Stérilité, Ovulation, Cycle menstruel, Epidémiologie, Facteur risque, Homme, Femelle, Etats Unis, Amérique du Nord, Amérique, Etude cohorte, Glande mammaire pathologie, Appareil génital femelle pathologie
Mots-clés Pascal anglais : Malignant tumor, Mammary gland, Sterility, Ovulation, Menstrual cycle, Epidemiology, Risk factor, Human, Female, United States, North America, America, Cohort study, Mammary gland diseases, Female genital diseases
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 98-0223953
Code Inist : 002B20E02. Création : 11/09/1998.