title: Physical Activity and Risk of Lung Cancer: A Meta-analysis.
abstract: OBJECTIVE
  Previous studies concerning the association between physical activity (PA) and risk of lung cancer yielded mixed results. We investigated the association by performing a meta-analysis.
  
  
  METHODS
  Relevant studies were identified by searching PubMed and EMBASE to January 2014. Twelve cohort studies and 6 case-control studies involving 2 468 470 participants and 26 453 cases of lung cancer were selected for meta-analysis.
  
  
  RESULTS
  We calculated the summary relative risk (RR) and 95% confidence intervals (CIs) using random-effects models. The analyses showed that individuals who participated in any amount of PA had an RR of 0.79 (95% CI, 0.73-0.86) for risk of lung cancer. Those who participated in high PA (vs low PA) had an RR of 0.75 (95% CI, 0.68-0.84). Stratifying by study design (case-control and cohort studies), smoking status (current, former, and never smokers), and gender, similar inverse associations were found for all the subgroups except for never smokers subgroup.
  
  
  CONCLUSIONS
  Pooled results from observational studies support a protective effect of PA against lung cancer.
authors.affiliation: *Center of Clinical Laboratory Science, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Nanjing, China; †Teaching and Research Office of General Surgery, Xuzhou Medical College, Xuzhou, China; and ‡Department of General Surgery, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Nanjing, China.
authors.forename: Shanliang
authors.initials: S
authors.lastname: Zhong
authors.forename: Tengfei
authors.initials: T
authors.lastname: Ma
authors.forename: Lin
authors.initials: L
authors.lastname: Chen
authors.forename: Weixian
authors.initials: W
authors.lastname: Chen
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Lv
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Zhang
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhao
mesh_terms: D015444:Exercise; D006801:Humans; D008175:Lung Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D064887:Observational Studies as Topic