title: Physical activity and risk of lymphoma: a meta-analysis.
abstract: BACKGROUND
  Physical activity has a protective effect on some types of cancer. The aim of the present meta-analysis was to explore the literature on the association between physical activity and risk of lymphoma.
  
  
  METHODS
  A meta-analysis was conducted for cohort and case-control studies examining the association between self-reported physical activity and risk of lymphoma. Depending on statistical heterogeneity, a random or fixed effects model was used to estimate the summary OR and corresponding 95% confidence interval (CI).
  
  
  RESULTS
  Seven case-control studies and 5 cohort studies were included. When data from both study designs were combined, no significant influence of physical activity on risk of lymphoma was found (pooled OR = 0.90; 95% CI: 0.79-1.02; P = 0.10). Subgroup analysis revealed a significant protective influence of physical activity on risk of lymphoma in case-control studies (pooled OR = 0.81; 95% CI: 0.68-0.96; P = 0.02). In contrast, cohort studies, which have a higher level of evidence than case-control studies, confirm the results of the primary meta-analysis (pooled OR = 1.02; 95% CI: 0.88-1.19; P = 0.76). A subsequent subgroup analysis found no significant differences between results for Hodgkin lymphoma and non-Hodgkin lymphoma (χ(2) = 0.16; P = 0.69), nor between results for recreational and occupational activities (χ(2) = 1.01; P = 0.31).
  
  
  CONCLUSIONS
  Epidemiologic research indicates no significant influence of physical activity on risk of lymphoma.
  
  
  CONCLUSIONS
  Future research should examine the association between sedentary behavior and risk of lymphoma and investigate the dose-response and timing effect of physical activity on risk of lymphoma.
authors.affiliation: Faculty of Kinesiology and Rehabilitation Sciences, KU Leuven Department of Rehabilitation Sciences, University Hospitals Leuven, Leuven Cancer Institute, KU Leuven, Leuven, Belgium.
authors.forename: Nele V H
authors.initials: NV
authors.lastname: Vermaete
authors.forename: Pascal
authors.initials: P
authors.lastname: Wolter
authors.forename: Gregor E G
authors.initials: GE
authors.lastname: Verhoef
authors.forename: Boudewijn J
authors.initials: BJ
authors.lastname: Kollen
authors.forename: Gert
authors.initials: G
authors.lastname: Kwakkel
authors.forename: Leen
authors.initials: L
authors.lastname: Schepers
authors.forename: Rik
authors.initials: R
authors.lastname: Gosselink
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D006801:Humans; D008223:Lymphoma / Q000453:epidemiology* / Q000209:etiology / Q000473:pathology; D009043:Motor Activity; D012307:Risk Factors