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Prospective assessment of breastfeeding and breast cancer incidence among 89,887 women.

Abstract

BACKGROUND

The relation between breastfeeding and breast cancer risk has been examined in many studies; some have reported no association, and others a reduced risk, particularly among premenopausal women. In the only prospective cohort study, no association was found. We have assessed prospectively the association between breastfeeding and incidence of breast cancer among 89,887 women in the US Nurses' Health Study.

METHODS

In 1986, participants were asked about the number of months they breastfed for all their children combined. Parous women with no history of cancer were included in this analysis. During 6 years of follow-up (513,015 person-years), 1,459 invasive breast cancer cases were diagnosed.

FINDINGS

Relative to women who had never breastfed, no significant overall association was found--after adjusting for established risk factors for breast cancer--between a history of having breastfed and subsequent development of breast cancer (relative risk [RR] 0.93, 95% CI 0.83 -1.03). No inverse trend was observed with duration of breastfeeding; women who breastfed for 2 years of longer had a RR of 1.11 (0.90-1.38). Among women who had given birth only once, women who had breastfed their child experienced a lower incidence of breast cancer (RR 0.68, 0.46-1.00). Among premenopausal women, who tended to be near menopause due to the age structure of the cohort, the RR of breast cancer for those who had lactated was 1.16 (0.89-1.50). Premenopausal women who had lactated for 1 year or more had a RR of 1.10 (0.78-1.57).

INTERPRETATION

These data suggest that there is no important overall association between breast-feeding and the occurrence of breast cancer.

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  • Authors+Show Affiliations

    ,

    Department of Epidemiology, Harvard School of Public Health, Boston, MA 02115, USA.

    , , , , , ,

    Source

    Lancet (London, England) 347:8999 1996 Feb 17 pg 431-6

    MeSH

    Adult
    Breast Feeding
    Breast Neoplasms
    Case-Control Studies
    Cohort Studies
    Female
    Humans
    Incidence
    Middle Aged
    Nurses
    Parity
    Postmenopause
    Premenopause
    Proportional Hazards Models
    Prospective Studies
    Risk Factors
    Time Factors
    United States

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't
    Research Support, U.S. Gov't, P.H.S.

    Language

    eng

    PubMed ID

    8618484

    Citation

    Michels, K B., et al. "Prospective Assessment of Breastfeeding and Breast Cancer Incidence Among 89,887 Women." Lancet (London, England), vol. 347, no. 8999, 1996, pp. 431-6.
    Michels KB, Willett WC, Rosner BA, et al. Prospective assessment of breastfeeding and breast cancer incidence among 89,887 women. Lancet. 1996;347(8999):431-6.
    Michels, K. B., Willett, W. C., Rosner, B. A., Manson, J. E., Hunter, D. J., Colditz, G. A., ... Speizer, F. E. (1996). Prospective assessment of breastfeeding and breast cancer incidence among 89,887 women. Lancet (London, England), 347(8999), pp. 431-6.
    Michels KB, et al. Prospective Assessment of Breastfeeding and Breast Cancer Incidence Among 89,887 Women. Lancet. 1996 Feb 17;347(8999):431-6. PubMed PMID: 8618484.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Prospective assessment of breastfeeding and breast cancer incidence among 89,887 women. AU - Michels,K B, AU - Willett,W C, AU - Rosner,B A, AU - Manson,J E, AU - Hunter,D J, AU - Colditz,G A, AU - Hankinson,S E, AU - Speizer,F E, PY - 1996/2/17/pubmed PY - 1996/2/17/medline PY - 1996/2/17/entrez SP - 431 EP - 6 JF - Lancet (London, England) JO - Lancet VL - 347 IS - 8999 N2 - BACKGROUND: The relation between breastfeeding and breast cancer risk has been examined in many studies; some have reported no association, and others a reduced risk, particularly among premenopausal women. In the only prospective cohort study, no association was found. We have assessed prospectively the association between breastfeeding and incidence of breast cancer among 89,887 women in the US Nurses' Health Study. METHODS: In 1986, participants were asked about the number of months they breastfed for all their children combined. Parous women with no history of cancer were included in this analysis. During 6 years of follow-up (513,015 person-years), 1,459 invasive breast cancer cases were diagnosed. FINDINGS: Relative to women who had never breastfed, no significant overall association was found--after adjusting for established risk factors for breast cancer--between a history of having breastfed and subsequent development of breast cancer (relative risk [RR] 0.93, 95% CI 0.83 -1.03). No inverse trend was observed with duration of breastfeeding; women who breastfed for 2 years of longer had a RR of 1.11 (0.90-1.38). Among women who had given birth only once, women who had breastfed their child experienced a lower incidence of breast cancer (RR 0.68, 0.46-1.00). Among premenopausal women, who tended to be near menopause due to the age structure of the cohort, the RR of breast cancer for those who had lactated was 1.16 (0.89-1.50). Premenopausal women who had lactated for 1 year or more had a RR of 1.10 (0.78-1.57). INTERPRETATION: These data suggest that there is no important overall association between breast-feeding and the occurrence of breast cancer. SN - 0140-6736 UR - https://www.unboundmedicine.com/medline/citation/8618484/Prospective_assessment_of_breastfeeding_and_breast_cancer_incidence_among_89887_women_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0140-6736(96)90010-0 DB - PRIME DP - Unbound Medicine ER -