AGES AT DIFFERENT REPRODUCTIVE EVENTS, NUMBERS OF MENSTRUAL CYCLES INBETWEEN AND BREAST-CANCER RISK

One hundred and seventy-five pathologically confirmed new cases of fem ale breast cancer in National Taiwan University Hospital were selected as the case group. Four hundred and fifty-seven inpatient controls we re individually matched for each case by age and date of admission. In formation of reproductive factors and potential confounders were colle cted from questionnaire interview and medical records. Menstrual cycle s before and after first fuIl-term pregnancy were estimated from the q uestionnaire. Conditional logistic regression was used to estimate the effects of reproductive risk factors and numbers of menstrual cycles before and after first full-term pregnancy. After adjusting for educat ional level, body mass index, family history of breast cancer and oral contraceptive use, age at menarche and menopause only showed borderli ne significance. Age at first full-term birth predicted breast cancer risk better. Parity was the most important protective factor. Number o f menstrual cycles before first full-term pregnancy was also positivel y associated with breast cancer risk with linear trends.