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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.

Abstract

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.

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  • Authors+Show Affiliations

    ,

    U.S. Department of Health and Human Services, Centers for Disease Control, Atlanta, GA 30333.

    , , , ,

    Source

    MeSH

    Adult
    Breast 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

    Pub Type(s)

    Clinical Trial
    Journal Article
    Multicenter Study
    Research Support, U.S. Gov't, P.H.S.

    Language

    eng

    PubMed ID

    2681548

    Citation

    Layde, P M., et al. "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." Journal of Clinical Epidemiology, vol. 42, no. 10, 1989, pp. 963-73.
    Layde PM, Webster LA, Baughman AL, et al. 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.
    Layde, P. M., Webster, L. A., Baughman, A. L., Wingo, P. A., Rubin, G. L., & Ory, H. W. (1989). 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. Journal of Clinical Epidemiology, 42(10), pp. 963-73.
    Layde PM, et al. 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. PubMed PMID: 2681548.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - 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. AU - Layde,P M, AU - Webster,L A, AU - Baughman,A L, AU - Wingo,P A, AU - Rubin,G L, AU - Ory,H W, PY - 1989/1/1/pubmed PY - 1989/1/1/medline PY - 1989/1/1/entrez SP - 963 EP - 73 JF - Journal of clinical epidemiology JO - J Clin Epidemiol VL - 42 IS - 10 N2 - 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. SN - 0895-4356 UR - https://www.unboundmedicine.com/medline/citation/2681548/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_ L2 - https://linkinghub.elsevier.com/retrieve/pii/0895-4356(89)90161-3 DB - PRIME DP - Unbound Medicine ER -