Long-term impact of combat-related concussions ‘have direct public health implications’

Service members with combat-related concussions demonstrated an evolution, rather than a resolution, of symptoms during a 5-year period, including selective worsening of cognitive function, according to findings published in Neurology.

These results refuted “the assumption that chronic stages of concussive injury are relatively stable,” according to the researchers, and suggested a need to reconsider the course of concussion outcomes in combat-deployed service members.

“Questions remain regarding the long-term outcome trajectories of service members who sustain traumatic brain injuries (TBI) in combat. Recent publications suggest these trajectories are not fully understood, in particular for mild TBI,” the researchers wrote. “The objective of the current study was to compare 1-year and 5-year clinical outcomes in these service members to better understand trajectories of long-term clinical outcome.”

Christine L. Mac Donald, PhD, professor of neurological surgery and research director of the Sports Institute at the University of Washington School of Medicine, and colleagues performed a prospective, observational, longitudinal multicohort study in four combat-deployed groups. These groups included non-head-injured controls with or without blast exposure and patients with combat-related concussions due to blast or blunt trauma. Researchers performed clinical evaluations at 1 and 5 years that consisted of identical batteries for neurobehavioral, psychiatric and cognitive outcomes. They enrolled patients between 2008 and 2013; the current study served as the 5-year evaluation. In all, 347 participants completed evaluations at both 1 and 5 years.

Findings demonstrated significant group differences cross-sectionally in both combat concussion groups at 5-year follow-up compared with controls in regard to both neurobehavioral symptoms, as measured by the Neurobehavioral Rating Scale-Revised (Cohen’s-d: -1.10 to -1.40; CIs, -0.82 to -1.32 to -0.97 to -1.83 by group), and psychiatric symptoms, as measured by Clinician-Administered PTSD Scale for DSM-IV (Cohen’s-d: -0.91 to -1.19; CIs, -0.63 to -1.19 to -0.76 to -1.62 by group). Researchers observed minimal differences in regard to cognitive performance.

Both combat concussion groups also demonstrated a clinically significant decrease in their 1- to 5-year evaluations (66% to 76% for neurobehavioral symptoms [Neurobehavioral Rating Scale-Revised]; 41% to 54% for psychiatric symptoms [Clinician-Administered PTSD Scale for DSM-IV] by group). Mac Donald and colleagues observed better results in both control groups, though a subset of these participants experienced clinically significant decline (37% to 50% for neurobehavioral symptoms [Neurobehavioral Rating Scale-Revised]; 9% to 25% for psychiatric symptoms [Clinician-Administered PTSD Scale for DSM-IV] by group).

Results of the present study have questioned “the historical consideration of ‘chronic’ injury as one group and underscore the need to consider clinically significant fluctuations even after the 6- to 12-month outcome,” according to Mac Donald and colleagues. The findings suggested that researchers cannot “merely lump” together all patients with TBI who have surpassed the 1-year point since their injury, as the courses of outcomes for these patients continue to change. This symptom evolution can impact conditions unrelated to the brain injury as service members age, Mac Donald and colleagues noted.

Researchers also extended this “trajectory comparison” to longitudinal outcomes in service members who had no head injury but were combat deployed, noting that they observed worsening trajectories in a number of non-blast controls, particularly in the domains of headache impairment, focal neurological deficits and mental health problems. These issues occurred to a lesser degree compared with patients who had a concussive blast TBI and non-blast TBI, but there was still a decline, according to Mac Donald and colleagues.

“There are over 18 million U.S. veterans of all previous conflicts alive today with TBI diagnosis from these conflicts and mild TBI in particular from recent conflicts impacting 20% [to] 40% of this population. These findings have direct public health implications, as many of these service members have decades of life to live with the hope that these would be good quality years,” the researchers wrote. “Understanding varying outcome trajectories will aid clinicians in identifying individuals requiring more targeted screening and treatment in order to help maintain better quality of life for our service men and women throughout their lifespan.”