title: Physical activity and survival in breast cancer.
abstract: Knowledge about lifestyle factors possibly influencing survival after breast cancer (BC) is paramount. We examined associations between two types of postdiagnosis physical activity (PA) and overall survival after BC.
  
  
  
  We used prospective data on 959 BC survivors from the Diet, Cancer, and Health cohort, all enrolled before diagnosis. Self-reported PA was measured as time per activity, and estimated metabolic equivalent task (MET)-hours per week were summed for each activity. We constructed measures for household, exercise, and total PA. The association between postdiagnosis PA and all-cause mortality was estimated as hazard ratio (HRs) based on Cox proportional hazards model, with time since diagnosis as the underlying time scale. Prediagnosis PA, body mass index (BMI), and receptor status were examined as potential effect modifiers.
  
  
  
  We identified 144 deaths from all causes during the study period. In adjusted analyses, exercise PA above eight MET h/week compared to lower levels of activity was significantly associated with improved overall survival (HR, 0.68; confidence interval [CI]: 0.47-0.99). When comparing participation in exercise to non-participation, we found a 44% risk reduction in overall survival (HR, 0.56; CI: 0.33-0.95). Neither between household nor total PA and overall survival did, we find significant associations. Prediagnosis PA, BMI, and receptor status did not modify the effect significantly.
  
  
  
  Exercise PA corresponding to 2.5 h or more of brisk weekly walking after BC diagnosis may reduce mortality by up to 32% compared to low-level exercise. Participation in exercise PA may reduce mortality by 44% compared to non-participation.
authors.affiliation: Survivorship Unit, Danish Cancer Society Research Center, Strandboulevarden 49, 2100 Copenhagen, Denmark; Institute of Sports Medicine and Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark. Electronic address: gunnam@cancer.dk.
authors.forename: Gunn
authors.initials: G
authors.lastname: Ammitzbøll
authors.affiliation: Institute of Sports Medicine and Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.
authors.forename: Karen
authors.initials: K
authors.lastname: Søgaard
authors.affiliation: Survivorship Unit, Danish Cancer Society Research Center, Strandboulevarden 49, 2100 Copenhagen, Denmark.
authors.forename: Randi V
authors.initials: RV
authors.lastname: Karlsen
authors.affiliation: Diet, Lifestyle and Genes, Danish Cancer Society Research Center, Strandboulevarden 49, 2100 Copenhagen, Denmark.
authors.forename: Anne
authors.initials: A
authors.lastname: Tjønneland
authors.affiliation: Survivorship Unit, Danish Cancer Society Research Center, Strandboulevarden 49, 2100 Copenhagen, Denmark; The Finsen Centre, Copenhagen University Hospital, Blegdamsvej 9, 2100 Copenhagen, Denmark.
authors.forename: Christoffer
authors.initials: C
authors.lastname: Johansen
authors.affiliation: Survivorship Unit, Danish Cancer Society Research Center, Strandboulevarden 49, 2100 Copenhagen, Denmark.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Frederiksen
authors.affiliation: Survivorship Unit, Danish Cancer Society Research Center, Strandboulevarden 49, 2100 Copenhagen, Denmark.
authors.forename: Pernille
authors.initials: P
authors.lastname: Bidstrup
mesh_terms: D015992:Body Mass Index; D001943:Breast Neoplasms / Q000401:mortality*; D003718:Denmark / Q000453:epidemiology; D004812:Epidemiologic Methods; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D040242:Risk Reduction Behavior
keywords: Breast cancer; Physical activity; Survival