Comparison of Clinical Outcomes 1 and 5 Years Post-Injury Following Combat Concussion

Neurology. 2021 Jan 19;96(3):e387-e398. doi: 10.1212/WNL.0000000000011089. Epub 2020 Nov 11.


Objective: To compare 1-year and 5-year clinical outcomes in 2 groups of combat-deployed service members without brain injury to those of 2 groups with combat-related concussion to better understand long-term clinical outcome trajectories.

Methods: This prospective, observational, longitudinal multicohort study examined 4 combat-deployed groups: controls without head injury with or without blast exposure and patients with combat concussion arising from blast or blunt trauma. One-year and 5-year clinical evaluations included identical batteries for neurobehavioral, psychiatric, and cognitive outcomes. A total of 347 participants completed both time points of evaluation. Cross-sectional and longitudinal comparisons were assessed. Overall group effect was modeled as a 4-category variable with rank regression adjusting for demographic factors using a 2-sided significance threshold of 0.05, with post hoc Tukey p values calculated for the pairwise comparisons.

Results: Significant group differences in both combat concussion groups were identified cross-sectionally at 5-year follow-up compared to controls in neurobehavioral (Neurobehavioral Rating Scale-Revised [NRS]; Cohen d, -1.10 to -1.40, confidence intervals [CIs] [-0.82, -1.32] to [-0.97, -1.83] by group) and psychiatric domains (Clinician-Administered PTSD Scale for DSM-IV [CAPS]; Cohen d, -0.91 to -1.19, CIs [-0.63, -1.19] to [-0.76, -1.62] by group) symptoms with minimal differences in cognitive performance. Both combat concussion groups also showed clinically significant decline from 1- to 5-year evaluation (66%-76% neurobehavioral NRS; 41%-54% psychiatric CAPS by group). Both control groups fared better but a subset also had clinically significant decline (37%-50% neurobehavioral NRS; 9%-25% psychiatric CAPS by group).

Conclusions: There was an evolution, not resolution, of symptoms from 1- to 5-year evaluation, challenging the assumption that chronic stages of concussive injury are relatively stable. Even some of the combat-deployed controls worsened. The evidence supports new considerations for chronic trajectories of concussion outcome in combat-deployed service members.

Publication types

  • Comparative Study
  • Observational Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Blast Injuries / diagnosis
  • Blast Injuries / psychology*
  • Brain Concussion / diagnosis
  • Brain Concussion / psychology*
  • Cognition / physiology*
  • Craniocerebral Trauma / psychology*
  • Disability Evaluation
  • Female
  • Humans
  • Longitudinal Studies
  • Male
  • Middle Aged
  • Military Personnel / psychology*
  • Neuropsychological Tests
  • Prospective Studies
  • Stress Disorders, Post-Traumatic / diagnosis*
  • Stress Disorders, Post-Traumatic / physiopathology