Menstrual and reproductive factors in relation to ovarian cancer risk

We assessed menstrual and reproductive factors in relation to ovarian cance r risk in a large, population-based, case-control study. 563 cases in Massa chusetts and New Hampshire were ascertained from hospitals and statewide tu mour registries; control women (n = 523) were selected through random digit dialing and matched to case women by age and telephone sampling unit. We u sed multivariate logistic regression to evaluate factors in relation to ris k of ovarian cancer and the major tumour histologic subtypes. Ovarian cance r risk was reduced among parous women, relative to nulliparous women (OR = 0.4; 95% CI = 0.3-0.6). Among parous women, higher parity (P = 0.0006), inc reased age at first (P = 0.03) or last (P = 0.05) birth. and time since las t birth (P = 0.04) were associated with reduced risk. Early pregnancy losse s, abortions, and stillbirths were unrelated to risk, but preterm, term, an d twin births were protective. Risk was lower among women who had breast-fe d. relative to those who had not (OR = 0.7: 95% CI = 0.5-1.0), but the aver age duration of breast-feeding per child was unrelated to risk (P for trend = 0.21). Age at menarche and age at menopause were unrelated to risk overa ll, although increasing menarcheal age was protective among premenopausal w omen (P = 0.02), Menstrual cycle characteristics and symptoms were generall y unrelated to risk, although cycle-related insomnia was associated with de creased risk (OR = 0.5; 95% CI = 0.3-0.8). We found no association between the type of sanitary product used during menstruation and ovarian cancer ri sk. In analyses by histologic subtype, reproductive and menstrual factors h ad most effect on risk of endometrioid/clear cell tumours, and least influe ntial with regard to risk of mucinous tumours. Overall, our findings offer some support to current hypotheses of ovarian pathogenesis, and show aetiol ogic differences among the tumour subtypes. (C) 2001 Cancer Research Campai gn.