The independent associations of parity, age at first full term pregnancy, and duration of breastfeeding with the risk of breast cancer. Cancer and Steroid Hormone Study Group. J Clin Epidemiol 1989;42(10):963-73
Date
01/01/1989Pubmed ID
2681548DOI
10.1016/0895-4356(89)90161-3Scopus ID
2-s2.0-0024448797 (requires institutional sign-in at Scopus site) 223 CitationsAbstract
Although the important influence of a woman's reproductive history on her risk of breast cancer is widely recognized, it is not clear whether this is wholly accounted for by the age at her first full-term pregnancy, or whether there are additional, independent influences of breastfeeding or number of children. To examine the respective contributions to the risk of breast cancer of these reproductive factors, we used logistic regression methods to analyze data from a multicenter case-control study, the Cancer and Steroid Hormone Study. Included in the analysis were 4599 women, 20-55 years of age, identified as having an initial diagnosis of breast cancer by one of eight collaborating population-based cancer registries. The 4536 controls were women of similar ages selected by random dialing of households with telephones in the same eight areas. As expected, age at first full-term pregnancy exerted a strong influence on the risk of breast cancer. However, after it and other potentially confounding factors had been controlled for, parity and duration of breastfeeding also had a strong influence on the risk of breast cancer. Compared with women of parity one, women of parity seven or greater had an adjusted relative risk of breast cancer of 0.59 (95% CL, 0.44-0.79). Compared with parous women who never breastfed, women who had breastfed for 25 months or more had an adjusted relative risk of 0.67 (0.52-0.85). These results do not support the supposed preeminent importance of age at first full-term pregnancy among the reproductive determinants of breast carcinogenesis. Resolution of this issue may have important implications for elucidating hormonal influences on breast cancer and for projecting future trends in the disease.
Author List
Layde PM, Webster LA, Baughman AL, Wingo PA, Rubin GL, Ory HWMESH terms used to index this publication - Major topics in bold
AdultBreast Feeding
Breast Neoplasms
Case-Control Studies
Data Interpretation, Statistical
Female
Humans
Interviews as Topic
Maternal Age
Middle Aged
Multicenter Studies as Topic
Odds Ratio
Parity
Risk
Time Factors
United States
