title: Medical therapy for diabetes is associated with increased use of lower endoscopy.
abstract: BACKGROUND
  Diabetes mellitus is associated with an increased risk of colorectal neoplasia and diabetes medications may further influence the risk. Observational studies of the effect of diabetes medications on colonic neoplasia may be biased if use of diabetes medications is associated with undergoing lower endoscopy. This study examined the association between diabetes therapies and use of lower endoscopy.
  
  
  METHODS
  This retrospective cohort study included patients with diabetes in an integrated, prepaid health plan. The primary exposure variables were use of sulfonylureas, metformin, thiazolidinediones (TZDs), and insulin. The outcome measure was completion of a flexible sigmoidoscopy or colonoscopy. Cox proportional hazards modeling, accounting for the time-varying nature of the medication exposures, was used to generate estimates of the relative hazard (HR) of lower endoscopy with different medications.
  
  
  RESULTS
  The study included 44 169 patients followed for a mean duration of 4.2 years (SD = 2.5 years); 34% underwent at least one lower endoscopy. Patients who filled a diabetes medication prescription were more likely to undergo lower endoscopy (HR = 1.13, 95%CI 1.06-1.21). Compared to those taking only sulfonylureas, patients receiving sulfonylureas and metformin (HR = 1.12, 95%CI 1.06-1.18) or metformin alone (HR = 1.17, 95%CI 1.07-1.26) were more likely to undergo lower endoscopy. For all medications, new use was associated with undergoing lower endoscopy (p < 0.05 for all comparisons).
  
  
  CONCLUSIONS
  Diabetic patients receiving medications are more likely to undergo lower endoscopy than those on diet control alone, particularly in the first year after initiating a new medication class and if taking metformin.
authors.affiliation: Department of Medicine, Division of Gastroenterology, Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, USA. lewisjd@mail.med.upenn.edu
authors.forename: James D
authors.initials: JD
authors.lastname: Lewis
authors.forename: Angela M
authors.initials: AM
authors.lastname: Capra
authors.forename: Ninah S
authors.initials: NS
authors.lastname: Achacoso
authors.forename: Assiamira
authors.initials: A
authors.lastname: Ferrara
authors.forename: Theodore R
authors.initials: TR
authors.lastname: Levin
authors.forename: Charles P
authors.initials: CP
authors.lastname: Quesenberry
authors.forename: Laurel A
authors.initials: LA
authors.lastname: Habel
mesh_terms: D000368:Aged; D015982:Bias; D015331:Cohort Studies; D003111:Colonic Polyps / Q000209:etiology*; D003113:Colonoscopy / Q000706:statistics & numerical data*; D015179:Colorectal Neoplasms / Q000209:etiology*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000188:drug therapy; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000009:adverse effects*; D007328:Insulin / Q000009:adverse effects; D008297:Male; D008687:Metformin / Q000009:adverse effects; D008875:Middle Aged; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012812:Sigmoidoscopy / Q000706:statistics & numerical data; D013453:Sulfonylurea Compounds / Q000009:adverse effects; D045162:Thiazolidinediones / Q000009:adverse effects
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D013453:Sulfonylurea Compounds; D045162:Thiazolidinediones; D008687:Metformin