title: Physical activity is associated with reduced risk of esophageal cancer, particularly esophageal adenocarcinoma: a systematic review and meta-analysis.
abstract: BACKGROUND
  Physical activity has been inversely associated with risk of several cancers. We performed a systematic review and meta-analysis to evaluate the association between physical activity and risk of esophageal cancer (esophageal adenocarcinoma [EAC] and/or esophageal squamous cell carcinoma [ESCC]).
  
  
  METHODS
  We conducted a comprehensive search of bibliographic databases and conference proceedings from inception through February 2013 for observational studies that examined associations between recreational and/or occupational physical activity and esophageal cancer risk. Summary adjusted odds ratio (OR) estimates with 95% confidence intervals (CI) were estimated using the random-effects model.
  
  
  RESULTS
  The analysis included 9 studies (4 cohort, 5 case-control) reporting 1,871 cases of esophageal cancer among 1,381,844 patients. Meta-analysis demonstrated that the risk of esophageal cancer was 29% lower among the most physically active compared to the least physically active subjects (OR, 0.71; 95% CI, 0.57-0.89), with moderate heterogeneity (I2 = 47%). On histology-specific analysis, physical activity was associated with a 32% decreased risk of EAC (4 studies, 503 cases of EAC; OR, 0.68; 95% CI, 0.55-0.85) with minimal heterogeneity (I2 = 0%). There were only 3 studies reporting the association between physical activity and risk of ESCC with conflicting results, and the meta-analysis demonstrated a null association (OR, 1.10; 95% CI, 0.21-5.64). The results were consistent across study design, geographic location and study quality, with a non-significant trend towards a dose-response relationship.
  
  
  CONCLUSIONS
  Meta-analysis of published observational studies indicates that physical activity may be associated with reduced risk of esophageal adenocarcinoma. Lifestyle interventions focusing on increasing physical activity may decrease the global burden of EAC.
authors.forename: Siddharth
authors.initials: S
authors.lastname: Singh
authors.forename: Swapna
authors.initials: S
authors.lastname: Devanna
authors.forename: Jithinraj
authors.initials: J
authors.lastname: Edakkanambeth Varayil
authors.forename: Mohammad Hassan
authors.initials: MH
authors.lastname: Murad
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Mayo Clinic, 200 First Street SW, Rochester 55905MN, USA. iyer.prasad@mayo.edu.
authors.forename: Prasad G
authors.initials: PG
authors.lastname: Iyer
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology*; D001471:Barrett Esophagus / Q000453:epidemiology*; D002294:Carcinoma, Squamous Cell / Q000453:epidemiology*; D004938:Esophageal Neoplasms / Q000453:epidemiology*; D000077277:Esophageal Squamous Cell Carcinoma; D015444:Exercise; D006801:Humans; D009043:Motor Activity; D065840:Protective Factors