title: The dose-response effect of physical activity on cancer mortality: findings from 71 prospective cohort studies.
abstract: BACKGROUND
  The WHO recommends moderate physical activity to combat the increasing risk of death from chronic diseases. We conducted a meta-analysis to assess the association between physical activity and cancer mortality and the WHO recommendations to reduce the latter.
  
  
  METHODS
  MEDLINE and EMBASE were searched up until May 2014 for cohort studies examining physical activity and cancer mortality in the general population and cancer survivors. Combined HRs were estimated using fixed-effect or random-effect meta-analysis of binary analysis. Associated HRs with defined increments and recommended levels of recreational physical activity were estimated by two-stage random-effects dose-response meta-analysis.
  
  
  RESULTS
  A total of 71 cohort studies met the inclusion criteria and were analysed. Binary analyses determined that individuals who participated in the most physical activity had an HR of 0.83 (95% CI 0.79 to 0.87) and 0.78 (95% CI 0.74 to 0.84) for cancer mortality in the general population and among cancer survivors, respectively. There was an inverse non-linear dose-response between the effects of physical activity and cancer mortality. In the general population, a minimum of 2.5 h/week of moderate-intensity activity led to a significant 13% reduction in cancer mortality. Cancer survivors who completed 15 metabolic equivalents of task (MET)-h/week of physical activity had a 27% lower risk of cancer mortality. A greater protective effect occurred in cancer survivors undertaking physical activity postdiagnosis versus prediagnosis, where 15 MET-h/week decreased the risk by 35% and 21%, respectively.
  
  
  CONCLUSIONS
  Our meta-analysis supports that current physical activity recommendations from WHO reduce cancer mortality in both the general population and cancer survivors. We infer that physical activity after a cancer diagnosis may result in significant protection among cancer survivors.
authors.affiliation: Department of Epidemiology and Biostatistics, and the Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Li
authors.affiliation: Department of Gastrointestinal Oncology, Hubei Cancer Hospital, Wuhan, Hubei, China.
authors.forename: Shaozhong
authors.initials: S
authors.lastname: Wei
authors.affiliation: Department of Epidemiology and Biostatistics, and the Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Department of Epidemiology and Biostatistics, and the Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Shuo
authors.initials: S
authors.lastname: Pang
authors.affiliation: Department of Epidemiology and Biostatistics, and the Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Qin
authors.affiliation: Department of Epidemiology and Biostatistics, and the Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Jieyun
authors.initials: J
authors.lastname: Yin
authors.affiliation: Department of Pathology, Hubei Cancer Hospital, Wuhan, Hubei, China.
authors.forename: Yunte
authors.initials: Y
authors.lastname: Deng
authors.affiliation: Department of Pathology, Hubei Cancer Hospital, Wuhan, Hubei, China.
authors.forename: Qiongrong
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Epidemiology and Biostatistics, and the Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Wei
authors.affiliation: Department of Epidemiology and Biostatistics, and the Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Shaofa
authors.initials: S
authors.lastname: Nie
authors.affiliation: Department of Epidemiology and Biostatistics, and the Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Li
authors.initials: L
authors.lastname: Liu
mesh_terms: D015444:Exercise; D006801:Humans; D009369:Neoplasms / Q000401:mortality* / Q000534:rehabilitation; D011446:Prospective Studies; D017741:Survivors; D014944:World Health Organization
keywords: Cancer; Death; Meta-analysis; Physical activity; Quantitative