title: Physical activity and risk of lung cancer: a meta-analysis of prospective cohort studies.
abstract: BACKGROUND
  Previous studies investigating the association of physical activity with risk of lung cancer reported conflicting results. In order to update and improve available evidence on any link, a meta-analysis was performed.
  
  
  METHODS
  We searched the PubMed database for prospective cohort studies investigating the relation of physical activity with risk of lung cancer. The pooled relative risk (RR) with its 95% confidence intervals (95%CI) was used to assess the association.
  
  
  RESULTS
  We included 14 prospective studies with a total of 1,644,305 participants, with 14,074 incident lung cancer cases documented during follow-up. Meta-analysis of all 14 studies suggested both high and medium levels of physical activity to be associated with decreased risk of lung cancer compared to the reference group with low level of physical activity (for high level, RR = 0.77, 95%CI 0.73-0.81, P < 0.001; for medium level, RR = 0.87, 95%CI 0.83-0.90, P < 0.001). Subgroup analyses by gender found obvious associations in both men and women. No publication bias was observed.
  
  
  CONCLUSIONS
  Our findings suggest that high and medium levels of physical activity have a beneficial effect on lung cancer by reducing the overall risk of tumour development among both men and women.
authors.affiliation: Department of Thoracic Surgery, Beijing Chest Hospital, Capital Medical University, Beijing, China.
authors.forename: Jia-Yang
authors.initials: JY
authors.lastname: Sun
authors.forename: Lei
authors.initials: L
authors.lastname: Shi
authors.forename: Xu-Dong
authors.initials: XD
authors.lastname: Gao
authors.forename: Shao-Fa
authors.initials: SF
authors.lastname: Xu
mesh_terms: D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000517:prevention & control; D008297:Male; D009043:Motor Activity; D011446:Prospective Studies