A population-based case-control study of breast cancer with a focus on premenopausal women under 45 years of age, conducted in three geographic regions of the United States, enabled the evaluation of risk in relation to varying breastfeeding practices. Among premenopausal parous women (1,211 cases, 1,120 random-digit-dialing controls), a history of breastfeeding for two or more weeks was associated with a relative risk (RR) of 0.87 (95 percent confidence interval [CI]=0.7–1.0). This relationship was not altered substantially by removing from the reference group women who had problems with breastfeeding in the first two weeks, including those with insufficient milk production. Risk was not related substantially to number of children breastfed or length of breastfeeding, although a relatively low risk was observed among those breastfeeding for the longest duration examined (RR=0.67, CI=0.4–1.1 for an average period per child of 72 or more weeks). Women who began to breastfeed at a young age (<22 years) experienced the greatest reduction in risk, but other timing parameters (e.g., interval since first or last breastfeeding) were not predictive of risk. Risks were not modified substantially by age or menopause status, although the number of menopausal subjects examined was limited. Use of medications to stop breast milk was unrelated to risk (RR=1.04). The results of this study do not support the notion that breastfeeding substantially reduces breast cancer risk; however, this may reflect the fact that most of our study subjects breastfed only for limited periods of time (average breastfeeding per child of 30 weeks). Further studies are needed to clarify the relationship of breastfeeding to breast cancer risk, and to determine possible etiologic mechanisms underlying any observed associations.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Price includes VAT (USA)
Tax calculation will be finalised during checkout.
MacMahon B, Lin TM, Lowe CR, et al. Lactation and cancer of the breast. A summary of an international study. Bull World Health Organ 1970; 42: 185–94.
Byers T, Graham S, Rzepka T, Marshall J. Lactation and breast cancer. Evidence for a negative association in premenopausal women. Am J Epidemiol 1985; 121: 664–74.
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. J Clin Epidemiol 1989; 42: 963–73.
McTiernan A, Thomas DB. Evidence for a protective effect of lactation on risk of breast cancer in young women. Am J Epidemiol 1986; 124: 353–8.
Newcomb PA, Storer BE, Longneeker MP, et al. Lactation and a reduced risk of premenopausal breast cancer. N Engl J Med 1994; 330: 81–7.
Tao SC, Yu MC, Ross RK, et al. Risk factors for breast cancer in Chinese women of Beijing. Int J Cancer 1988; 42: 495–8.
United Kingdom National Case-Control Study Group. Breastfeeding and risk of breast cancer in young women. Br Med J 1993; 307: 17–20.
Yang CP, Weiss NS, Band PR, et al. History of lactation and breast cancer risk. Am J Epidemiol 1993; 138: 1050–6.
Yoo KY, Tajima K, Kuroishi T, et al. Independent protective effect of lactation against breast cancer. A case-control study in Japan. Am J Epidemiol 1992; 135: 726–33.
Yuan JM, Yu MC, Ross RK, et al. Risk factors for breast cancer in Chinese women in Shanghai. Cancer Res 1988; 48: 1949–53.
Adami HO, Bergstrom R, Lund E, et al. Absence of association between reproductive variables and the risk of breast cancer in young women in Sweden and Norway. Br J Cancer 1990; 62: 122–6.
Haring MH, Rookus MA, Van Leeuwen FE. Beschermt het geven van borstvoeding tegen borstkanker? Een epidemiologisch onderzock. (Does breastfeeding protect against breast cancer? An epidemiological study). Ned Tijdschr Geneeskd 1992; 136: 743–7.
Kalache A, Vessey MP, McPherson K. Lactation and breast cancer. Br Med J 1980; 280: 223–4.
Kvale G, Heuch I. Lactation and cancer risk: Is there a relation specific to breast cancer? J Epidemiol Comm Health 1987; 42: 30–7.
London SJ, Colditz GA, Stampfer MJ, et al. Lactation and risk of breast cancer in a cohort of US women. Am J Epidemiol 1990; 132: 17–26.
Rosero-Bixby L, Oberle MW, Lee NC. Reproductive history and breast cancer in a population of high fertility, Costa Rica, 1984–85. Int J Cancer 1987; 40: 747–54.
Siskind V, Schofield F, Rice D, et al. Breast cancer and breastfeeding: Results from an Australian case-control study. Am J Epidemiol 1989; 130: 229–36.
Thomas DB, Noonan EA, the WHO Collaborative Study of Neoplasia and Steroid Contraceptives, Breast cancer and prolonged lactation. Int J Epidemiol 1993; 22: 619–26.
Waksberg J. Sampling methods for random digit dlaling. J Am Stat Assoc 1978; 73: 40–6.
Breslow NE, Day NE. Statistical Methods in Cancer Research. Vol 1. The Analysis of Casecontrol Studies. Lyon, France: International Agency for Research on Cancer, 1980; IARC Sci. Pub. No. 32.
Brinton LA, Daling JR, Liff J. et al. Oral contraceptives and breast cancer risk among younger women. JNCI 1995, in press.
MacMahon B, Purde M, Cramer D, et al. Association of breast cancer risk with age at first and subsequent births: A study in the population of the Estonian Republic. JNCI 1982; 69: 1035–8.
Henderson BE, Ross RK, Judd HL, et al. Do regular ovulatory cycles increase breast cancer risk? Cancer 1985; 56: 1206–8.
Howie PW, McNeilly AS, Houston MJ, et al. Effect of supplementary food on suckling patterns and ovarian activity during lactation. Br Med J 1981; 283: 757–9.
Henderson BE, Ross RK, Pike MC, Casagrande JT. Endogenous hormones as a major risk factor in human cancer. Cancer Res 1982; 42: 3232–9.
Petrakis NL, Wrensch MR, Ernster VL, et al. Influence of pregnancy and lactation on serum and breast fluid estrogen levels: Implications for breast cancer risk. Int J Cancer 1987; 40: 587–91.
Vorherr H, Messer RH. Breast cancer: Potentially predisposing and protecting factors. Am J Obstet Gynecol 1978; 130: 335–58.
Kurinij N, Shiono PH, Ezrine SF, et al. Does maternal employment affect breast-feeding? Am J Public Health 1989; 79: 1247–50.
Ryan AS, Rush D, Krieger FW, et al. Recent declines in breast-feeding in the United States, 1984 through 1989. Pediatrics 1991; 88: 719–27.
Drs Brinton, Potischman, and Swanson are with the Environmental Epidemiology Branch, National Cancer Institute, Betbesda, MD, USA. Authors also are affiliated with the Special Epidemiology Program, New Jersey State Department of Health, Trenton, NJ, USA (Ms Schoenberg); Rollins School of Public Health, Emory University, Atlanta, GA, USA (Dr Coates); the Division of Epidemiology, Columbia University School of Public Health, New York, NY, USA (Dr Gammon); and the Fred Hutchinson Cancer Research Center, University of Washington, Seattle, WA (Drs Malone, Stanford, Daling). Address correspondence to Dr Brinton, Environmental Epidemiology Branch, National Cancer Institute, Executive Plaza North, Room 443, Bethesda, MS 20892, USA.
About this article
Cite this article
Brinton, L.A., Potischman, N.A., Swanson, C.A. et al. Breastfeeding and breast cancer risk. Cancer Causes Control 6, 199–208 (1995). https://doi.org/10.1007/BF00051791
- Breast cancer
- breast feeding
- United States