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Lactation and incidence of premenopausal breast cancer: a longitudinal study.

Abstract

BACKGROUND

Findings from observational studies suggest an inverse association between lactation and premenopausal breast cancer risk, but results are inconsistent, and data from large prospective cohort studies are lacking.

METHODS

We used information from 60,075 parous women participating in the prospective cohort study of the Nurses' Health Study II from 1997 to 2005. Our primary outcome was incident premenopausal breast cancer.

RESULTS

We ascertained 608 incident cases of premenopausal breast cancer during 357,556 person-years of follow-up. Women who had ever breastfed had a covariate-adjusted hazard ratio (HR) of 0.75 (95% confidence interval [CI], 0.56-1.00) for premenopausal breast cancer compared with women who had never breastfed. No linear trend was found with duration of total lactation (P = .95), exclusive lactation (P = .74), or lactation amenorrhea (P = .88). The association between lactation and premenopausal breast cancer was modified by family history of breast cancer (P value for interaction = .03). Among women with a first-degree relative with breast cancer, those who had ever breastfed had a covariate-adjusted HR of 0.41 (95% CI, 0.22-0.75) for premenopausal breast cancer compared with women who had never breastfed, whereas no association was observed among women without a family history of breast cancer.

CONCLUSION

In this large, prospective cohort study of parous premenopausal women, having ever breastfed was inversely associated with incidence of breast cancer among women with a family history of breast cancer.

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  • Authors+Show Affiliations

    ,

    Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, School of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA. astuebe@med.unc.edu

    , ,

    Source

    Archives of internal medicine 169:15 2009 Aug 10 pg 1364-71

    MeSH

    Adult
    Breast Feeding
    Breast Neoplasms
    Cohort Studies
    Female
    Genetic Predisposition to Disease
    Humans
    Incidence
    Longitudinal Studies
    Middle Aged
    Parity
    Pregnancy
    Premenopause
    Proportional Hazards Models
    Risk
    Risk Factors

    Pub Type(s)

    Journal Article
    Research Support, N.I.H., Extramural

    Language

    eng

    PubMed ID

    19667298

    Citation

    Stuebe, Alison M., et al. "Lactation and Incidence of Premenopausal Breast Cancer: a Longitudinal Study." Archives of Internal Medicine, vol. 169, no. 15, 2009, pp. 1364-71.
    Stuebe AM, Willett WC, Xue F, et al. Lactation and incidence of premenopausal breast cancer: a longitudinal study. Arch Intern Med. 2009;169(15):1364-71.
    Stuebe, A. M., Willett, W. C., Xue, F., & Michels, K. B. (2009). Lactation and incidence of premenopausal breast cancer: a longitudinal study. Archives of Internal Medicine, 169(15), pp. 1364-71. doi:10.1001/archinternmed.2009.231.
    Stuebe AM, et al. Lactation and Incidence of Premenopausal Breast Cancer: a Longitudinal Study. Arch Intern Med. 2009 Aug 10;169(15):1364-71. PubMed PMID: 19667298.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Lactation and incidence of premenopausal breast cancer: a longitudinal study. AU - Stuebe,Alison M, AU - Willett,Walter C, AU - Xue,Fei, AU - Michels,Karin B, PY - 2009/8/12/entrez PY - 2009/8/12/pubmed PY - 2009/8/21/medline SP - 1364 EP - 71 JF - Archives of internal medicine JO - Arch. Intern. Med. VL - 169 IS - 15 N2 - BACKGROUND: Findings from observational studies suggest an inverse association between lactation and premenopausal breast cancer risk, but results are inconsistent, and data from large prospective cohort studies are lacking. METHODS: We used information from 60,075 parous women participating in the prospective cohort study of the Nurses' Health Study II from 1997 to 2005. Our primary outcome was incident premenopausal breast cancer. RESULTS: We ascertained 608 incident cases of premenopausal breast cancer during 357,556 person-years of follow-up. Women who had ever breastfed had a covariate-adjusted hazard ratio (HR) of 0.75 (95% confidence interval [CI], 0.56-1.00) for premenopausal breast cancer compared with women who had never breastfed. No linear trend was found with duration of total lactation (P = .95), exclusive lactation (P = .74), or lactation amenorrhea (P = .88). The association between lactation and premenopausal breast cancer was modified by family history of breast cancer (P value for interaction = .03). Among women with a first-degree relative with breast cancer, those who had ever breastfed had a covariate-adjusted HR of 0.41 (95% CI, 0.22-0.75) for premenopausal breast cancer compared with women who had never breastfed, whereas no association was observed among women without a family history of breast cancer. CONCLUSION: In this large, prospective cohort study of parous premenopausal women, having ever breastfed was inversely associated with incidence of breast cancer among women with a family history of breast cancer. SN - 1538-3679 UR - https://www.unboundmedicine.com/medline/citation/19667298/Lactation_and_incidence_of_premenopausal_breast_cancer:_a_longitudinal_study_ L2 - https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/10.1001/archinternmed.2009.231 DB - PRIME DP - Unbound Medicine ER -