Key Points
Question
What clinical measures collected acutely in combat are associated with 5-year outcome in patients with concussive blast injury?
Findings
In this longitudinal cohort study, nonmedically evacuated blast concussion patients had significant and sustained symptoms of neurobehavioral impairment, mental health and global disability, whereas cognitive changes were unremarkable compared with combat-deployed nonconcussed controls. Assessments collected in theater were associated with multiple domains of outcome.
Meaning
Nonmedically evacuated patients with concussive blast injury, considered the mildest of the mild combat casualties fared poorly 5 years later compared with combat-deployed controls.
ObjectiveTo compare 1-year and 5-year clinical outcomes in 2 groups of combat-deployed-non-brain-injured service members to 2 groups of combat-related concussion to better understand long-term clinical outcome trajectories.MethodsThis prospective, observational, longitudinal multi-cohort study examined 4 combat-deployed groups: non-head-injured controls with or without blast exposure, and patients with combat concussion arising from blast or blunt trauma. 1-year and 5-year clinical evaluations included identical batteries for neurobehavioral, psychiatric, and cognitive outcomes. Three hundred forty-seven participants completed both time points of evaluation. Cross-sectional and longitudinal comparisons were assessed. Overall group-effect was modelled as a four-category variable with rank regression adjusting for demographic factors using a two-sided significance threshold of 0.05, with post-hoc Tukey p-values calculated for the pairwise comparisons.ResultsSignificant group differences in both combat concussion groups were identified cross-sectionally at 5-year follow-up compared to controls in domains of neurobehavioral-NRS (Cohen's-d, −1.10 to −1.40, CIs [−0.82: −1.32] to [−0.97: −1.83] by group), and psychiatric-CAPS (Cohen's-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% neurobehavior-NRS; 41%–54% psychiatric-CAPS by group). Both control groups fared better but a subset also had clinically significant decline (37%–50% neurobehavior-NRS; 9%–25% psychiatric-CAPS by group).ConclusionsThere 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.
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