gms | German Medical Science

MAINZ//2011: 56. GMDS-Jahrestagung und 6. DGEpi-Jahrestagung

Deutsche Gesellschaft für Medizinische Informatik, Biometrie und Epidemiologie e. V.
Deutsche Gesellschaft für Epidemiologie e. V.

26. - 29.09.2011 in Mainz

Breast cancer risk among women with long-standing lactation: a case-control study in Northern Tanzania

Meeting Abstract

  • Irmgard Jordan - Justus-Liebig-University Giessen, Giessen
  • Antje Hebestreit - Bremen Institute for Preventive Research and Social Medicine, Bremen
  • Britta Swai - Kilimanjaro Christian Medical Center, Moshi
  • Michael B Krawinkel - Justus-Liebig-University Giessen, Giessen

Mainz//2011. 56. Jahrestagung der Deutschen Gesellschaft für Medizinische Informatik, Biometrie und Epidemiologie (gmds), 6. Jahrestagung der Deutschen Gesellschaft für Epidemiologie (DGEpi). Mainz, 26.-29.09.2011. Düsseldorf: German Medical Science GMS Publishing House; 2011. Doc11gmds393

doi: 10.3205/11gmds393, urn:nbn:de:0183-11gmds3932

Published: September 20, 2011

© 2011 Jordan et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Introduction: Breast cancer is the leading cause of death among women worldwide. Studies in industrialised countries identified age at menarche, age at first full-term pregnancy, and especially lactation as determining factors in the aetiology of breast cancer. Our study investigates for the first time an association of breast cancer risk in a community where children are commonly breastfed for 2 years.

Methods: 115 female breast cancer patients (cases) and 230 age- and district-matched women clinically free from breast cancer (controls) were interviewed about their reproductive history and socioeconomic condition. Semi-structured interviews including anthropometric measurements were conducted by trained enumerators.

Results: The median age was 50 years (min/max 26 to 85 years). Estimated median BMI at age 20 was 21kg/m² in both cases and controls. Median lifelong lactation of the mothers was 96 months (cases) and 108 months (controls). The odds ratio for lifelong lactation was slightly below one (OR 0.99 95% CI 0.98–1.00, p < 0.01). There was no significant association in risk for BMI at interview (median 25kg/m² of cases and 26 kg/m² of controls), age at menarche (median 16 years), and age at first full-term pregnancy (median 20 years). Late age at menarche and prolonged lifelong lactation were associated with a risk reduction among premenopausal women (ORmenarche 0.74 95% CI 0.56-1.00, p=0.05; ORlactation 0.98 95%CI 0.97-0.99, p<0.01).

Conclusion: Our results confirm that long-standing lactation is associated with a lower breast cancer risk. However, current changes in lifestyle affect the lifelong lactation and increased incidence of breast cancer is to be expected. Promotion of breastfeeding should include its effect on maternal health.


Jordan I, Hebestreit A, Swai B, Krawinkel MB. Breast cancer risk among women with long-standing lactation and reproductive parameters at low risk level: a case-control study in Northern Tanzania. Breast Cancer Res. 2010.