title: Recent recreational physical activity and breast cancer risk in postmenopausal women in the E3N cohort.
abstract: BACKGROUND
  Physical activity probably protects against the risk of breast cancer after menopause, but questions remain about how rapidly and for how long this protective effect exists.
  
  
  METHODS
  We analyzed data from 59,308 postmenopausal women (2,155 incident invasive breast cancers) followed between 1993 and 2005 (8.5 years postmenopause on average) through biennial questionnaires. Multivariable Cox models included time-varying exposure data, using levels of recreational physical activity self-reported in 1993, 1997, and 2002.
  
  
  RESULTS
  Women with recent (within the previous 4 years) recreational physical activity levels ≥12 metabolic equivalent task-hours (MET-h)/week had a lower risk of invasive breast cancer than women with lower levels [HR, 0.90; 95% confidence interval (CI), 0.82-0.99], with no apparent dose-response relation beyond 12 MET-h/week. Associations did not vary significantly across ER/PR subtypes. Risk reductions were of the same magnitude order regardless of weight change, body mass index, waist circumference, or less recent (5-9 years earlier) physical activity levels. Among women with levels of physical activity ≥12 MET-h/week 5 to 9 years earlier, those who became less active (<12 MET-h/week) had a significantly increased risk of breast cancer compared with those who did not (HR, 1.16; 95% CI, 1.01-1.35). And, compared with the least active women at both time points, they had no significantly decreased risk of breast cancer (HR, 1.06; 95% CI, 0.87-1.29).
  
  
  CONCLUSIONS
  Our results suggest a decrease in risk associated with recent recreational physical activity even of modest levels.
  
  
  CONCLUSIONS
  Starting or maintaining physical activity after menopause may be beneficial regarding breast cancer risk.
authors.affiliation: Inserm, CESP Centre for Research in Epidemiology and Population Health, Nutrition, Hormones and Women's Health Team, Villejuif, France. Univ Paris Sud, Villejuif, France. IGR Institut Gustave Roussy, Villejuif, France.
authors.forename: Agnès
authors.initials: A
authors.lastname: Fournier
authors.affiliation: Inserm, CESP Centre for Research in Epidemiology and Population Health, Nutrition, Hormones and Women's Health Team, Villejuif, France. Univ Paris Sud, Villejuif, France. Laboratoire CIAMS Complexité, Innovation, et Activités Motrices et Sportives, Univ Paris Sud, Orsay, France.
authors.forename: Gaël
authors.initials: G
authors.lastname: Dos Santos
authors.affiliation: Inserm, CESP Centre for Research in Epidemiology and Population Health, Nutrition, Hormones and Women's Health Team, Villejuif, France. Univ Paris Sud, Villejuif, France. IGR Institut Gustave Roussy, Villejuif, France.
authors.forename: Gwenaëlle
authors.initials: G
authors.lastname: Guillas
authors.affiliation: Laboratoire CIAMS Complexité, Innovation, et Activités Motrices et Sportives, Univ Paris Sud, Orsay, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Bertsch
authors.affiliation: Department of Sport Medicine and Functional Exploration, Univ Hospital CHU G. Montpied; INRA, UNH, CRNH Auvergne, University of Auvergne, Clermont-Ferrand, France.
authors.forename: Martine
authors.initials: M
authors.lastname: Duclos
authors.affiliation: Inserm, CESP Centre for Research in Epidemiology and Population Health, Nutrition, Hormones and Women's Health Team, Villejuif, France. Univ Paris Sud, Villejuif, France. IGR Institut Gustave Roussy, Villejuif, France.
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Boutron-Ruault
authors.affiliation: Inserm, CESP Centre for Research in Epidemiology and Population Health, Nutrition, Hormones and Women's Health Team, Villejuif, France. Univ Paris Sud, Villejuif, France. IGR Institut Gustave Roussy, Villejuif, France. francoise.clavel@gustaveroussy.fr.
authors.forename: Françoise
authors.initials: F
authors.lastname: Clavel-Chapelon
authors.affiliation: Inserm, CESP Centre for Research in Epidemiology and Population Health, Nutrition, Hormones and Women's Health Team, Villejuif, France. Univ Paris Sud, Villejuif, France. IGR Institut Gustave Roussy, Villejuif, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Mesrine
mesh_terms: D001943:Breast Neoplasms / Q000453:epidemiology*; D015331:Cohort Studies; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D008875:Middle Aged; D009043:Motor Activity; D017698:Postmenopause; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011998:Recreation; D012307:Risk Factors; D011795:Surveys and Questionnaires