Reproductive factors and breast cancer risk among older women
Reproductive factors have been shown to affect pre- and postmenopausal breast cancer risk differently, but whether there are additional age-specific differences among menopausal women as they age has not been clarified. We analyzed data from a large population-based case–control study that included 1,508 breast cancer cases and 1,556 controls, aged 20–98 years, who completed an in-home interviewer-administered questionnaire. The following subgroups were created to examine if the associations between reproductive factors and breast cancer risk varied by age- and menopausal-status: premenopausal (n = 968), postmenopausal <65 years (n = 1,045), postmenopausal ≥65 years (n = 958). Among postmenopausal women ≥65 years, ever having breastfed decreased risk (odds ratio (OR) = 0.67, 95% confidence interval (CI) = 0.48, 0.92), and a strong dose–response relationship was observed for longer durations of breastfeeding (P trend = 0.02), with the most pronounced protective effect observed for ≥14 months of breastfeeding (OR = 0.40, 95% CI = 0.21,0.76). Late age at first birth (AFB) and older age at last birth (ALB) were associated with non-statistically significant increases in breast cancer risk in this older group, while late age at menarche and surgical menopause decreased risk. ORs for multiparity were close to the null. Among premenopausal women and postmenopausal women <65 years, multiparity significantly decreased risk, and older AFB nonsignificantly increased risk. Our findings suggest that the well-known protective effect of multiparity attenuates with older age. Moreover, breastfeeding, one of the few potentially modifiable risk factors for breast cancer, was an important factor in decreasing risk among older parous postmenopausal women.
KeywordsBreast cancer Breastfeeding Age at first birth Age at last birth Parity Premenopausal Postmenopausal Age
Unable to display preview. Download preview PDF.
This work was supported in part by grants from the National Cancer Institute and the National Institute of Environmental Health Sciences (Grant nos. UO1CA/ES66572, T32CA09330, P30ES09089, and P30ES10126). For their valuable contributions to the Long Island Breast Cancer Study Project the authors thank: members of the Long Island Breast Cancer Network; the 31 participating institutions on Long Island and in New York City, NY; our National Institutes of Health collaborators, Gwen Collman, Ph.D., National Institutes of Environmental Health Sciences; G. Iris Obrams, M.D., Ph.D. formerly of the National Cancer Institute; members of the External Advisory Committee: Leslie Bernstein, Ph.D., (Committee chair); Gerald Akland, M.S.; Barbara Balaban, MSW; Blake Cady, M.D.; Dale Sandler, Ph.D.; Roy Shore, Ph.D.; and Gerald Wogan, Ph.D.; as well as other collaborators who assisted with various aspects of our data collection efforts including Mary Wolff, Ph.D.; Geoff Kabat, Ph.D.; Steve Stellman, Ph.D.; Maureen Hatch, Ph.D.; Gail Garbowski, MPH; H. Leon Bradlow, Ph.D.; Martin Trent, B.S.; Ruby Senie, Ph.D.; Carla Maffeo, Ph.D.; Pat Montalvan; Gertrud Berkowitz, Ph.D.; Margaret Kemeny, M.D.; Mark Citron, M.D.; Freya Schnabel, M.D.; Allen Schuss, M.D.; Steven Hajdu, M.D.; and Vincent Vinciguerra, M.D. For their careful review of the manuscript, the authors would also like to thank Andrew Olshan, Ph.D., and Stephen Kritchevsky, Ph.D.
- 3.Ries LAG et al (2000) SEER cancer statistics review. National Cancer Institute, Bethesda(MD) pp 1973–1997Google Scholar
- 10.Collaborative Group on Hormonal Factors in Breast Cancer (2002) Breast cancer and breastfeeding: collaborative reanalysis of individual data from 47 epidemiological studies in 30 countries, including 50302 women with breast cancer and 96973 women without the disease. Lancet 360(9328):187–195Google Scholar
- 12.Gammon M, Neugut AI, Santella RM, Teitelbaum SL, Britton JA, Terry MB, Eng SM, Wolff MS, Stellman SD, Kabat GC, Levin B, Bradlow HL, Hatch M, Beyea J, Camann D, Trent M, Senie RT, Garbowski GC, Maffeo C,␣Montalvan P, Berkowitz GS, Kemeny M, Citron M, Schnabe F, Schuss A, Hajdu S, Vincguerra V, Collman GW, Obrams GI (2002) The Long Island breast cancer study project: description of a multi-institutional collaboration to identify environmental risk factors for breast cancer. Breast Cancer Res Treat 3:235–254CrossRefGoogle Scholar
- 14.Hosmer D, Lemeshow S (1989) Applied logistic regression. John Wiley and Sons Inc, New YorkGoogle Scholar
- 17.McTiernan A, Thomas DB (1989) Evidence for a protective effect of lactation on risk of breast cancer in young women. Results from a case-control study. Am J Epidemiol 124(3):353–358Google Scholar
- 18.Layde P, Webster LA, Baughman AL, Wingo PA, Rubin GL, Ory HW (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. J Clin Epidemiol 42(10):963–973PubMedCrossRefGoogle Scholar
- 20.United Kingdom National Case–Control Study Group (1993) Breast feeding and risk of breast cancer in young women. Br Med J 307(6895):17–20Google Scholar
- 27.Russo J, Russo IH (1994) Toward a physiological approach to breast cancer prevention. Cancer Epidemiology Biomarkers Prev 3(4):353–364Google Scholar
- 46.Guralnik JM, LaCroix AZ, Everett DF, Kovar MG (1989) Aging in the eighties: the prevalence of comorbidity, its association with disability. National Center for Health Statistics, Advanced Data from Vital and Health Statistics. MD, Hyattsville,. p. 179Google Scholar
- 51.Walker RA et al (1996) Breast carcinomas occurring in young women (<35 years) are different. Br J Cancer 315:1796–1800Google Scholar