B – 117 Remote Mild Traumatic Brain Injury is Not Associated with Worse Cognitive and Alzheimer’s Disease Markers in Mild Cognitive Impairment

Abstract Objective Remote traumatic brain injury (TBI) has been linked to earlier cognitive decline, potentially from reduced cognitive reserve or increased Alzheimer’s pathophysiology. However, it is unclear if mild TBI (mTBI) may have a similar association, and if so, the possible mechanism. This exploratory study examined if a history of mTBI was linked to differences in age of onset, cognition, and Alzheimer’s biomarkers in amnestic mild cognitive impairment (aMCI). Method Thirty-three participants with aMCI from a dementia-specialty clinic at UT Southwestern completed a TBI interview, lumbar puncture, and neuropsychological assessment. Thirteen measures were administered to assess memory, language, visuospatial, attention, and executive function. Cerebrospinal fluid (CSF) concentrations of amyloid beta 42/40, phosphorylated tau181 (Ptau181), and total tau were obtained. Remote mTBI history was present for 19 individuals (mTBI+) and absent in 14 (mTBI-). Independent samples t-tests compared each variable between groups, with effect sizes calculated. Results Age of symptom onset (p=.089, d=.665) and aMCI diagnosis (p=.048, d=.828) occurred 5.3-5.6 years earlier in the mTBI+ group with moderate-to-large effects. However, Ptau181 was lower for the mTBI+ than the mTBI- group with a medium-to-large effect (p=.057, d=.730). No group differences emerged on other biomarkers or cognitive performance (p>.05, d<.50). Conclusion History of mTBI may be linked to earlier onset/diagnosis based on this small study, but was unrelated with reduced cognitive performance or elevated CSF-derived markers of Alzheimer’s pathophysiology. Findings suggest mTBI might make some prone to earlier aMCI onset. A mechanistic link for earlier onset is unknown though, and future work should investigate other possible mechanisms and/or biomarkers.