title: Prevalence of lost-time claims for mild traumatic brain injury in the working population: improving estimates using workers compensation databases.
abstract: OBJECTIVE
  To test the usefulness of a method to improve the measurement of prevalent mild traumatic brain injury (MTBI) among injured workers with a workers compensation claim.
  
  
  METHODS
  Database codes were selected to identify MTBI cases in the Ontario workers compensation lost-time claims database. A random sample of 210 claims was selected, classified as MTBI or not, and used to calculate proportions with MTBI among code groups. The annual prevalence of MTBI in 1997 and 1998 was calculated by weighting the numerators with the appropriate proportions of MTBI within each code group.
  
  
  RESULTS
  Four code groups were created: the head region, cranial region, concussion code group and the brain region. The proportion of MTBI in each group was 29%, 19%, 92% and 32%, respectively. The 1997 prevalence depended on the codes used, from 39/10,000 (95% confidence interval (CI): 35-44) for a weighted version of the 'concussion' code to 58/10,000 (95% CI: 50-65) for inclusion of all identified MTBI codes.
  
  
  CONCLUSIONS
  Restricting the enumeration of MTBI to specific 'concussion' codes can lead to under-estimation of the prevalence of MTBI in epidemiological studies using workers compensation data. Approximately six out of every 1000 lost-time claims are associated with MTBI. Given lost-time estimates of disability under-estimate the prevalence of this mild injury, MTBI, is an important workplace injury.
authors.affiliation: Centre of Research Expertise in Improved Disability Outcomes, University Health Network, Toronto Western Hospital, Toronto, Ontario, Canada. vicki.kristman@uhnresearch.ca
authors.forename: Vicki L
authors.initials: VL
authors.lastname: Kristman
authors.forename: Pierre
authors.initials: P
authors.lastname: Côté
authors.forename: Dwayne
authors.initials: D
authors.lastname: Van Eerd
authors.forename: Marjan
authors.initials: M
authors.lastname: Vidmar
authors.forename: Mana
authors.initials: M
authors.lastname: Rezai
authors.forename: Sheilah
authors.initials: S
authors.lastname: Hogg-Johnson
authors.forename: Richard A
authors.initials: RA
authors.lastname: Wennberg
authors.forename: J David
authors.initials: JD
authors.lastname: Cassidy
mesh_terms: D000062:Accidents, Occupational / Q000145:classification / Q000706:statistics & numerical data; D000293:Adolescent; D000328:Adult; D000368:Aged; D001930:Brain Injuries / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology*; D016208:Databases, Factual; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D015588:Observer Variation; D009864:Ontario / Q000453:epidemiology; D015995:Prevalence; D014942:Workers' Compensation / Q000706:statistics & numerical data*