Higher Cerebrospinal Fluid Levels of Amyloid-β40 Following Traumatic Brain Injury Relate to Confrontation Naming Performance

Abstract

Background: Traumatic brain injury (TBI) may confer risk for Alzheimer’s disease (AD) through amyloid-β (Aβ) overproduction. However, the relationship between TBI and Aβ levels in cerebrospinal fluid (CSF) remains unclear. Objective: To explore whether Aβ overproduction is implicated in the relationship between TBI and AD, we compared CSF levels of Aβ in individuals with a TBI history versus controls (CTRLs) and related CSF Aβ levels to cognitive markers associated with preclinical AD. Methods: Participants were 112 non-impaired Veterans (TBI = 56, CTRL = 56) from the Alzheimer’s Disease Neuroimaging Initiative-Department of Defense database with available cognitive data (Boston Naming Test [BNT], Rey Auditory Verbal Learning Test [AVLT]) and CSF measures of Aβ42, Aβ40, and Aβ38. Mediation models explored relationships between TBI history and BNT scores with Aβ peptides as mediators. Results: The TBI group had higher CSF Aβ40 (t = –2.43, p = 0.017) and Aβ38 (t = –2.10, p = 0.038) levels than the CTRL group, but groups did not differ in CSF Aβ42 levels or Aβ42/Aβ40 ratios (p > 0.05). Both Aβ peptides negatively correlated with BNT (Aβ40: rho = –0.20, p = 0.032; Aβ38: rho = –0.19, p = 0.048) but not AVLT (p > 0.05). Aβ40 had a significant indirect effect on the relationship between TBI and BNT performance (β= –0.16, 95% CI [–0.393, –0.004], PM = 0.54). Conclusions: TBI may increase AD risk and cognitive vulnerability through Aβ overproduction. Biomarker models incorporating multiple Aβ peptides may help identify AD risk among those with TBI.