Blast Exposure Does Not Increase Blood Biomarkers of Neurodegeneration in Service Members and Veterans with and Without Uncomplicated Mild TBI

Abstract

Prior investigations of how lifetime blast exposure relates to blood biomarkers of brain injury have been limited by small sample sizes and have produced conflicting results. This investigation examined how lifetime blast exposure relates to glial fibrillary acidic protein (GFAP), ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1), neurofilament light (NfL), tau, and hyperphosphorylated tau (p-tau) in service members and veterans (SMVs) with and without uncomplicated mild TBI (mTBI). Participants were 422 SMVs prospectively enrolled in a Defense and Veterans Brain Injury Center-Traumatic Brain Injury Center of Excellence Longitudinal TBI Study. Participants were divided into four groups based on self-reported lifetime blast exposure history as assessed by a single question: none (n = 93), low (n = 136), medium (n = 71), and high (n = 122). Analysis of Covariance was used to examine group differences on GFAP, UCH-L1, NfL, tau, and p-tau. There was a significant effect of blast exposure group on NfL (p = 0.002, η_p ²= 0.034) and GFAP (p = 0.035, η_p ²= 0.021), but not UCH-L1, tau, or p-tau. Post hoc comparisons with Bonferroni correction indicated NfL was higher in the No Blast group compared with the Low Blast (p = 0.004) group, but not the Medium Blast (p = 0.069) or High Blast (p = 1.0) groups. GFAP did not significantly differ between the groups after Bonferroni correction (ps > 0.05). Overall, the lone finding that survived correction for multiple comparisons suggested that participants with low levels of self-reported blast exposure exhibited lower levels of NfL than participants with no history of blast exposure. There were no differences in UCH-L1, tau, or p-tau based on self-reported blast exposure in a large sample of SMVs with and without mTBI.