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Methods Inf Med 2009; 48(05): 444-450
DOI: 10.3414/ME9239
Original Articles
Schattauer GmbH

Physical Activity and Postmenopausal Breast Cancer

Effect Modification by Other Breast Cancer Risk Factors

Authors

  • M. E. Schmidt

    1   Unit of Environmental Epidemiology, German Cancer Research Center, Heidelberg, Germany

  • J. Chang-Claude

    2   Department of Cancer Epidemiology, German Cancer Research Center, Heidelberg, Germany

  • T. Slanger

    2   Department of Cancer Epidemiology, German Cancer Research Center, Heidelberg, Germany

  • N. Obi

    3   Institute for Medical Biometrics and Epidemiology, University Clinic Hamburg-Eppendorf, Hamburg, Germany

  • D. Flesch-Janys

    3   Institute for Medical Biometrics and Epidemiology, University Clinic Hamburg-Eppendorf, Hamburg, Germany

  • K. Steindorf

    1   Unit of Environmental Epidemiology, German Cancer Research Center, Heidelberg, Germany
Further Information

Publication History

20 August 2009

Publication Date:
20 January 2018 (online)

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Summary

Objectives: Epidemiological evidence suggests an inverse association between physical activity (PA) and postmenopausal breast cancer risk. Breast cancer is a heterogeneous disease, influenced by reproductive factors, lifestyle pattern, and predispositions. We investigated whether these risk factors modify the effect of PA on breast cancer risk.

Methods: We analyzed data from 2004 hormone-receptor-positive postmenopausal breast cancer cases and 6569 controls from the population-based MARIE study conducted 2002–2005 in Germany. Interaction was statistically tested using adjusted unconditional logistic regression models.

Results: The inverse association between leisure-time PA and risk of postmenopausal hormone-receptor-positive breast cancer was not heterogeneous by family history of breast cancer or by hormone therapy. PA showed a significant interaction with benign breast diseases (p = 0.023) and with breastfeeding (p = 0.045) but not with parity (p = 0.94), with clear risk reductions only for women who ever had breastfed or who ever had a benign breast disease (among ever breastfed: odds ratio = 0.63; 95% confidence interval = (0.52, 0.77), highest vs. lowest PA quartile). Interaction with BMI was weak (p = 0.053).

Conclusions: Breastfeeding and benign breast diseases modified the effect of PA on postmenopausal breast cancer risk. If other studies find similar modifications, increasing knowledge about these risk factors may contribute to a better understanding of the mode of action of PA on breast cancer risk. For women who are at higher risk for breast cancer due to family history or due to hormone therapy use, it is encouraging that they might lower their risk by being physically active.

Keywords

Postmenopausal breast cancer - physical activity - effect modification - case-control study