title: Physical Activity and Risk of Colon Cancer in Diabetic and Nondiabetic US Adults.
abstract: OBJECTIVE
  To determine whether moderate to vigorous physical activity is associated with a decreased risk of colon cancer in diabetic patients.
  
  
  METHODS
  We evaluated the association between physical activity and colon cancer in 25,753 patients with a self-reported history of diabetes and in 274,965 nondiabetic individuals from the National Institutes of Health-AARP Diet and Health Study who were aged 50 to 71 years in 1995-1996. Moderate to vigorous physical activity was assessed at baseline using a self-administered questionnaire. Follow-up for colon cancer incidence extended to December 31, 2011.
  
  
  RESULTS
  During 13.0 years of follow-up, 480 diabetic patients and 4151 nondiabetic individuals had development of colon cancer. Among diabetic patients, compared with never/rarely engaging in physical activity, more than 7 h/wk of physical activity exhibited a reduced risk of colon cancer in the age- and sex-adjusted model (hazard ratio [HR], 0.74; 95% CI, 0.56-0.996; P=.16 for trend). This association was attenuated and no longer statistically significant after additional control for other covariates (HR, 0.78; 95% CI, 0.58-1.05; P=.29 for trend). By comparison, physical activity was inversely related to colon cancer risk in nondiabetic individuals (multivariate-adjusted HR, 0.81; 95% CI, 0.73-0.89; P<.001 for trend).
  
  
  CONCLUSIONS
  In this investigation of the relationship between physical activity and colon cancer in diabetic patients, we found a statistically significant inverse relationship in the age- and sex-adjusted model, which was no longer statistically significant in the multivariate-adjusted model. A reduced risk was noted among nondiabetic individuals, irrespective of other covariates. Future studies with a larger number of participants are required to explore whether physical activity beneficially affects colon cancer risk among diabetic patients.
authors.affiliation: Department of Epidemiology and Preventive Medicine, University of Regensburg, Regensburg, Germany. Electronic address: daniela.schmid@klinik.uni-regensburg.de.
authors.forename: Daniela
authors.initials: D
authors.lastname: Schmid
authors.affiliation: Department of Epidemiology and Preventive Medicine, University of Regensburg, Regensburg, Germany.
authors.forename: Gundula
authors.initials: G
authors.lastname: Behrens
authors.affiliation: Division of Cancer Epidemiology and Genetics, Metabolic Epidemiology Branch, National Cancer Institute, Bethesda, MD.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Matthews
authors.affiliation: Department of Epidemiology and Preventive Medicine, University of Regensburg, Regensburg, Germany.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Leitzmann
mesh_terms: D000368:Aged; D015984:Causality; D003110:Colonic Neoplasms / Q000453:epidemiology*; D015897:Comorbidity; D048909:Diabetes Complications / Q000453:epidemiology*; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D015444:Exercise; D005260:Female; D005500:Follow-Up Studies; D015438:Health Behavior; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D009316:National Institutes of Health (U.S.); D016017:Odds Ratio; D018570:Risk Assessment; D014481:United States / Q000453:epidemiology