J Neurotrauma. 2023 Aug 31. doi: 10.1089/neu.2023.0133. Online ahead of print.
The purpose of this study was to extend previous research by examining the relationship between lifetime blast exposure (LBE) and neurobehavioral functioning following mild TBI (MTBI) by using a comprehensive measure of lifetime blast exposure. Participants were 103 United States SMVs with a medically documented diagnosis of MTBI, recruited from three military treatment facilities (74.8%) and community-based recruitment initiatives (25.2%, e.g., social media, flyers). Participants completed a battery of neurobehavioral measures 12-or-more months post-injury (NSI, PCLC, TBI-QOL); including the Blast Exposure Threshold Survey (BETS). The sample was classified into two LBE groups: High (n=57) and Low (n=46) LBE. In addition, the sample was classified into four LBE/PTSD subgroups: High PTSD/High LBE (n=38); High PTSD/Low LBE (n=19); Low PTSD/High LBE (n=19); and Low PTSD/Low LBE (n=27). The High LBE group had consistently worse scores on all neurobehavioral measures compared to the Low LBE group. However, when controlling for the influence of PTSD (using ANCOVA), only a handful of group differences remained. When comparing measures across the four LBE/PTSD subgroups, in the absence of clinically meaningful PTSD symptoms (i.e., Low PTSD), participants with High LBE had worse scores on the majority of neurobehavioral measures (e.g., postconcussion symptoms, sleep, fatigue). When examining the total number of clinically elevated measures, the High LBE subgroup consistently had a greater number of clinically elevated scores compared to the Low LBE group for the majority of comparisons (i.e., 4- to 15-or-more elevated symptoms). In contrast, in the presence of clinically meaningful PTSD symptoms (i.e., High PTSD), there were no differences between High versus Low LBE subgroups for all measures. However, when examining the total number of clinically elevated measures, there were meaningful differences between High versus Low LBE groups for those comparisons that included a high number of clinically elevated scores (i.e., 6- to 10-or-more), but not for a low number of clinically elevated scores (i.e., 1- to 5-or-more). High LBE, as quantified using a more comprehensive measure than utilized in past research (i.e., BETS), was associated with worse overall neurobehavioral functioning following MTBI. This study extends existing literature showing that LBE, that is largely sub-concussive, may negatively impact warfighter brain health and readiness beyond diagnosable brain injury.