This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Margolis, K. L. Articles by Weiderpass, E. Search for Related Content PubMed PubMed Citation Articles by Margolis, K. L. Articles by Weiderpass, E.

Physical Activity in Different Periods of Life and the Risk of Breast Cancer: The Norwegian-Swedish Women's Lifestyle and Health Cohort Study

¹ Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; ² Division of Clinical Epidemiology, Hennepin County Medical Center, Minneapolis, Minnesota; ³ Department of Epidemiology, Harvard University School of Public Health, Boston, Massachusetts; ⁴ Institute of Community Medicine, University of Tromsø, Tromsö, Norway; and ⁵ Finnish Cancer Registry, Helsinki, Finland; and ⁶ Cancer Registry of Norway, Oslo, Norway

Requests for reprints: Karen L. Margolis, Berman Center for Outcomes and Clinical Research, Division of Clinical Epidemiology, Hennepin County Medical Center, Suite 440, 825 South 8th Street, Minneapolis, MN 55404. Phone: 612-347-2179; Fax: 612-341-7935. E-mail: margo006{at}umn.edu.

Background: Physical activity has been found to be associated with decreased risk of breast cancer in postmenopausal women in the majority of epidemiologic studies, but the association is inconsistent in premenopausal women.

Methods: We studied the effect of physical activity at various ages on the incidence of breast cancer in 99,504 women from 30 to 49 years of age at enrollment in the Women's Lifestyle and Health Study, a prospective population-based cohort study in Norway and Sweden. Physical activity level on an ordinal scale at age 14, age 30, and age at enrollment, participation in competitive sports, as well as information on other covariates was obtained using a self-administered questionnaire. Complete follow-up with data on incident invasive breast cancer and mortality was collected by linkage to national registries. The relation between physical activity and time to breast cancer development was assessed using Cox proportional hazard models, controlling for potential confounders.

Results: During an average 9.1 years of follow-up, there were 1,166 incident breast cancer cases. The mean age of the women was 41 years at enrollment, and the mean age at breast cancer diagnosis was 48 years. Compared to inactive women, women with higher levels of physical activity at enrollment had a similar risk of incident breast cancer (adjusted relative risk, 1.24 for vigorous activity compared with no activity; 95% CI, 0.85-1.82). Physical activity at age 30 or at age 14 also did not afford any significant protection from breast cancer, nor did a consistently high level of activity from younger ages to enrollment.

Conclusions: We did not find evidence of a protective effect of physical activity on breast cancer risk in this group of primarily premenopausal women.

Key Words: breast neoplasms • physical activity • cohort study • Breast cancer • Diet, alcohol, smoking, and other lifestyle risk factors

This article has been cited by other articles:

				S. S. Maruti, W. C. Willett, D. Feskanich, B. Rosner, and G. A. Colditz A Prospective Study of Age-Specific Physical Activity and Premenopausal Breast Cancer J Natl Cancer Inst, May 21, 2008; 100(10): 728 - 737. [Abstract] [Full Text] [PDF]

				C. M. Dallal, J. Sullivan-Halley, R. K. Ross, Y. Wang, D. Deapen, P. L. Horn-Ross, P. Reynolds, D. O. Stram, C. A. Clarke, H. Anton-Culver, et al. Long-term Recreational Physical Activity and Risk of Invasive and In Situ Breast Cancer: The California Teachers Study Arch Intern Med, February 26, 2007; 167(4): 408 - 415. [Abstract] [Full Text] [PDF]

				B. Tehard, C. M. Friedenreich, J.-M. Oppert, and F. Clavel-Chapelon Effect of Physical Activity on Women at Increased Risk of Breast Cancer: Results from the E3N Cohort Study Cancer Epidemiol. Biomarkers Prev., January 1, 2006; 15(1): 57 - 64. [Abstract] [Full Text] [PDF]

				H. J. Baer, S. J. Schnitt, J. L. Connolly, C. Byrne, W. C. Willett, B. Rosner, and G. A. Colditz Early Life Factors and Incidence of Proliferative Benign Breast Disease Cancer Epidemiol. Biomarkers Prev., December 1, 2005; 14(12): 2889 - 2897. [Abstract] [Full Text] [PDF]

				A. Malin, C. E. Matthews, X.-O. Shu, H. Cai, Q. Dai, F. Jin, Y.-T. Gao, and W. Zheng Energy Balance and Breast Cancer Risk Cancer Epidemiol. Biomarkers Prev., June 1, 2005; 14(6): 1496 - 1501. [Abstract] [Full Text] [PDF]