Lactation and breast cancer risk: a case-control study in Connecticut

In this report, we examined the relationship between lactation and breast c ancer risk, in a case-control study of breast cancer, conducted in Connecti cut between 1994 and 1998. Included were 608 incident breast cancer cases a nd 609 age frequency matched controls, aged 30-80 years old, Cases and cont rols were interviewed by trained study interviewers, using a standardized, structured questionnaire, to obtain information on lactation and other majo r risk factors, Parous women who reported ever lactation had a borderline s ignificantly reduced risk of breast cancer (OR = 0.83, 95% CI, 0.63-1.09). An OR of 0.53 (95% CI, 0.27-1.04) was observed in those having breastfed mo re than 3 children compared to those who never lactated. Women having breas tfed their first child for more than 13 months had an OR of 0.47 (95% CI, 0 .23-0.94) compared to those who never breastfed. Lifetime duration of lacta tion also showed a risk reduction while none of the ORs were statistically significant. Further stratification by menopausal status showed a risk redu ction related to lactation for both pre- and postmenopausal women, while th e relationship is less consistent for the latter. These results support an inverse association between breastfeeding and breast cancer risk. (C) 2001 Cancer Research Campaign.