Physical Activity and Breast Cancer Risk: The European Prospective Investigation into Cancer and Nutrition

^{1 1}Department of Epidemiology, German Institute of Human Nutrition Potsdam-Rehbrücke, Nuthetal, Germany; ²Division of Population Health and Information, Alberta Cancer Board, Calgary, Alberta, Canada; ³National Institute of Public Health and the Environment, Bilthoven, the Netherlands; ⁴Institute of Health Sciences, Vrije Universiteit, Amsterdam, the Netherlands; ⁵Molecular and Nutritional Epidemiology Unit, Centro per lo Studio e la Prevenzione Oncologica, Scientific Institute of Tuscany, Florence, Italy; ⁶Cancer Research UK, Epidemiology Unit, University of Oxford, Oxford, United Kingdom; ⁷Department of Public Health and Primary Care, School of Clinical Medicine, University of Cambridge, United Kingdom; ⁸MRC Dunn Human Nutrition Unit, Cambridge, United Kingdom; ⁹MRC Centre for Nutritional Epidemiology in Cancer Prevention and Survival, Department of Public Health and Primary Care, University of Cambridge, United Kingdom; ¹⁰Julius Center for Health Sciences and Primary Care, University Medical Center, Utrecht, Netherlands; ¹¹Department of Clinical Sciences in Malmö, Clinical Research Center, Lund University, Lund, Sweden; ¹²Department of Surgery, Malmö University Hospital, Malmö, Sweden; ¹³Department of Epidemiology, Catalan Institute of Oncology, Institut d'Investigació Biomèdica de Bellvitge, Barcelona, Spain; ¹⁴Public Health Institute of Navarra, Pamplona, Spain; ¹⁵Department of Public Health of Gipuzkoa, San Sebastian, Spain; ¹⁶Health Information Unit, Public Health and Planning Directorate, Health and Health Services Council, Principality of Asturias, Oviedo, Spain; ¹⁷Epidemiology Department, Murcia Health Council, Murcia, Spain; ¹⁸Andalusian School of Public Health, Granada, Spain; ¹⁹Epidemiology Unit, National Cancer Institute, Milan, Italy; ²⁰Cancer Registry, Azienda Ospedaliera "Civile-M.P. Arezzo," Ragusa, Italy; ²¹Department of Clinical and Experimental Medicine, Federico II University, Naples, Italy; ²²Imperial College London, and University of Torino, Turin, Italy; ²³Department of Hygiene and Epidemiology, School of Medicine, University of Athens, Athens, Greece; ²⁴Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts; ²⁵Division of Clinical Epidemiology, German Cancer Research Center, Heidelberg, Germany; ²⁶Institut National de la Santé et de la Recherche Médicale, ERI20, Institut Gustave Roussy, Villejuif, France; ²⁷Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark; ²⁸Department of Clinical Epidemiology, Aalborg Hospital and Aarhus University Hospital, Aalborg, Denmark; ²⁹Nutrition and Hormones Group, IARC (WHO), Lyon, France; ³⁰Division of Cancer Epidemiology, German Cancer Research Center, Heidelberg, Germany; and ³¹Department of Epidemiology and Public Health, Faculty of Medicine, Imperial College, London, United Kingdom

^* To whom correspondence should be addressed. E-mail: Petra.Lahmann{at}mrc-hnr.cam.ac.uk.

	Abstract

There is convincing evidence for a decreased risk of breast cancer with increased physical activity. Uncertainties remain, however, about the role of different types of physical activity on breast cancer risk and the potential effect modification for these associations. We used data from 218,169 premenopausal and postmenopausal women from nine European countries, ages 20 to 80 years at study entry into the European Prospective Investigation into Cancer and Nutrition. Hazard ratios (HR) from multivariate Cox regression models were calculated using metabolic equivalent value-based physical activity variables categorized in quartiles, adjusted for age, study center, education, body mass index, smoking, alcohol use, age at menarche, age at first pregnancy, parity, current oral contraceptive use, and hormone replacement therapy use. The physical activity assessment included recreational, household, and occupational activities. A total physical activity index was estimated based on cross-tabulation of these separate types of activity. During 6.4 years of follow-up, 3,423 incident invasive breast cancers were identified. Overall, increasing total physical activity was associated with a reduction in breast cancer risk among postmenopausal women (P_trend = 0.06). Specifically, household activity was associated with a significantly reduced risk in postmenopausal (HR, 0.81; 95% confidence interval, 0.70-0.93, highest versus the lowest quartile; P_trend = 0.001) and premenopausal (HR, 0.71; 95% confidence interval, 0.55-0.90, highest versus lowest quartile; P_trend = 0.003) women. Occupational activity and recreational activity were not significantly related to breast cancer risk in both premenopausal and postmenopausal women. This study provides additional evidence for a protective effect of physical activity on breast cancer risk. (Cancer Epidemiol Biomarkers Prev 2007;16(1):OF1-7)

Key Words: physical activity, household activity, breast neoplasm, menopausal status

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