title: Detection bias may be the main cause of increased cancer incidence among diabetics: results from the Rotterdam Study.
abstract: OBJECTIVE
  Type 2 diabetes is associated with an increased cancer risk. Most studies on this topic analyse diabetes as a risk factor without adjusting for diabetes duration before cancer occurrence. This study aimed to investigate the association between diabetes duration and cancer risk in more detail.
  
  
  METHODS
  In this prospective cohort study, diabetes diagnosis was based on clinical information and use of glucose lowering medication. Details on incident cancers were obtained via general practitioners and linkage to pathology registers. Cox proportional hazards models were used with onset and duration of diabetes as time-varying determinants.
  
  
  RESULTS
  The study comprised 10,181 individuals. Diabetes was associated with an increased overall risk of incident cancers (hazard ratio (HR) 1.2, 95% confidence interval (CI) 1.07-1.39) and pancreatic cancer (HR 2.9, 95% CI 1.75-4.89). A diagnosis of diabetes less than three months before the diagnosis of cancer was associated with strongly increased risks of all- (HR 3.3, 95% CI 2.50-4.32) and pancreatic cancers (HR 28.7, 95% CI 6.32-130.58).
  
  
  CONCLUSIONS
  The magnitude of the association between diabetes and an increased risk of cancer seems to be inflated by detection- or protopathic bias. Future studies investigating this association should adjust for diabetes duration and include a plausible aetiological risk window.
authors.affiliation: Department of Surgery, Erasmus Medical Center, Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands. Electronic address: k.debruijn@erasmusmc.nl.
authors.forename: Kirstin M J
authors.initials: KM
authors.lastname: De Bruijn
authors.affiliation: Department of Epidemiology, Erasmus Medical Center, Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands. Electronic address: r.ruiter@erasmusmc.nl.
authors.forename: Rikje
authors.initials: R
authors.lastname: Ruiter
authors.affiliation: Department of Epidemiology, Erasmus Medical Center, Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands; The Health Care Inspectorate, The Hague, The Netherlands. Electronic address: c.dekeyser@erasmusmc.nl.
authors.forename: Catherine E
authors.initials: CE
authors.lastname: de Keyser
authors.affiliation: Department of Epidemiology, Erasmus Medical Center, Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands. Electronic address: a.hofman@erasmusmc.nl.
authors.forename: Albert
authors.initials: A
authors.lastname: Hofman
authors.affiliation: Department of Epidemiology, Erasmus Medical Center, Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands; The Health Care Inspectorate, The Hague, The Netherlands. Electronic address: b.stricker@erasmusmc.nl.
authors.forename: Bruno H
authors.initials: BH
authors.lastname: Stricker
authors.affiliation: Department of Surgery, Erasmus Medical Center, Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands. Electronic address: c.vaneijck@erasmusmc.nl.
authors.forename: Casper H J
authors.initials: CH
authors.lastname: van Eijck
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D015331:Cohort Studies; D016001:Confidence Intervals; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors
keywords: Cancer incidence; Cohort study; Detection bias; Diabetes mellitus