title: Television viewing and time spent sedentary in relation to cancer risk: a meta-analysis.
abstract: BACKGROUND
  Sedentary behavior is emerging as an independent risk factor for chronic disease and mortality. However, the evidence relating television (TV) viewing and other sedentary behaviors to cancer risk has not been quantitatively summarized.
  
  
  METHODS
  We performed a comprehensive electronic literature search in Cochrane, EMBASE, Medline, and SciSearch databases through February 2014 for published articles investigating sedentary behavior in relation to cancer incidence. Because randomized controlled trials are difficult to perform on this topic, we focused on observational studies that met uniform inclusion criteria. Data were extracted independently by both authors and summarized using random-effects meta-analysis and meta-regression. All statistical tests were two-sided.
  
  
  RESULTS
  Data from 43 observational studies including a total of 68936 cancer cases were analyzed. Comparing the highest vs lowest levels of sedentary time, the relative risks (RRs) for colon cancer were 1.54 (95% confidence interval [CI] = 1.19 to 1.98) for TV viewing time, 1.24 (95% CI = 1.09 to 1.41) for occupational sitting time, and 1.24 (95% CI = 1.03 to 1.50) for total sitting time. For endometrial cancer, the relative risks were 1.66 (95% CI = 1.21 to 2.28) for TV viewing time and 1.32 (95% CI = 1.08 to 1.61) for total sitting time. A positive association with overall sedentary behavior was also noted for lung cancer (RR = 1.21; 95% CI = 1.03 to 1.43). Sedentary behavior was unrelated to cancers of the breast, rectum, ovaries, prostate, stomach, esophagus, testes, renal cell, and non-Hodgkin lymphoma.
  
  
  CONCLUSIONS
  Prolonged TV viewing and time spent in other sedentary pursuits is associated with increased risks of certain types of cancer.
authors.affiliation: Affiliation of authors: Department of Epidemiology and Preventive Medicine, University of Regensburg, Regensburg, Germany (DS, MFL). daniela.schmid@klinik.uni-regensburg.de.
authors.forename: Daniela
authors.initials: D
authors.lastname: Schmid
authors.affiliation: Affiliation of authors: Department of Epidemiology and Preventive Medicine, University of Regensburg, Regensburg, Germany (DS, MFL).
authors.forename: Michael F
authors.initials: MF
authors.lastname: Leitzmann
mesh_terms: D000428:Alcohol Drinking; D003110:Colonic Neoplasms / Q000453:epidemiology / Q000378:metabolism; D015986:Confounding Factors, Epidemiologic; D016889:Endometrial Neoplasms / Q000453:epidemiology / Q000378:metabolism; D004734:Energy Metabolism; D005247:Feeding Behavior; D005260:Female; D014943:Global Health; D006801:Humans; D015994:Incidence; D007333:Insulin Resistance; D007899:Leisure Activities; D008175:Lung Neoplasms / Q000453:epidemiology / Q000378:metabolism; D009369:Neoplasms / Q000453:epidemiology* / Q000378:metabolism*; D009765:Obesity / Q000453:epidemiology / Q000209:etiology; D064887:Observational Studies as Topic / Q000592:standards; D009790:Occupations; D058028:Research Report / Q000592:standards*; D018570:Risk Assessment; D012307:Risk Factors; D057185:Sedentary Behavior; D011795:Surveys and Questionnaires; D013690:Television; D013997:Time Factors; D014481:United States / Q000453:epidemiology; D015430:Weight Gain