Systematic bias in outcome studies of persons with traumatic brain injury

Arch Phys Med Rehabil. 1997 Feb;78(2):132-7. doi: 10.1016/s0003-9993(97)90253-7.


Objective: (1) Examine systematic biases created by subjects lost at 1-year follow-up in samples of persons with traumatic brain injury; (2) identify potential threats to generalization of outcomes data.

Design: A consecutive sample of admissions to acute rehabilitation studied 1 year following discharge.

Setting: An inpatient brain injury rehabilitation unit in a large, academic medical center.

Subjects: Eighty-eight patients with primary diagnosis of traumatic brain injury.

Main outcome measures: Subjects were considered lost to follow-up when phone calls, mail, clinic visits, and assistance from family failed to allow contact 1 year after discharge from acute rehabilitation. Potential effects of the biased follow-up sample were examined for seven suboptimal outcomes.

Results: A total of 38.6% of subjects were lost to follow-up. Subjects intoxicated at time of injury and those with history of substance abuse were more-likely to be lost. Among subjects followed, the likelihood of working or being in school 1 year after discharge was significantly less for those intoxicated at time of injury and those with a history of substance abuse.

Conclusions: Systematic bias in longitudinal studies may result from subjects with substance use problems being lost to follow-up. Population estimates for return to work or school will be overestimated if those lost who have substance use problems resemble those followed.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Brain Injuries / etiology
  • Brain Injuries / rehabilitation*
  • Ethanol / blood
  • Female
  • Follow-Up Studies
  • Humans
  • Longitudinal Studies
  • Male
  • Outcome Assessment, Health Care
  • Substance-Related Disorders / complications


  • Ethanol