Traumatic brain injury and post-traumatic stress disorder on brain imaging markers and cognition in a war veterans population

BackgroundTraumatic brain injury (TBI) and post-traumatic stress disorder (PTSD) are emerging contributors to the development and progression of dementia.ObjectiveThis study examined how traumatic brain injury and post-traumatic stress disorder relate to cognitive function and neuroimaging markers in U.S. veterans from the Department of Defense Alzheimer's Disease Neuroimaging Initiative (ADNI-DOD).MethodsTBI severity was quantified with a new scoring system, and PTSD symptoms and combat exposure were assessed using the Clinician-Administered PTSD Scale (CAPS) and Combat Exposure Scale (CES). Cognitive performance was evaluated with the Mini-Mental State Examination (MMSE), Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog), and Clinical Dementia Rating Sum of Boxes (CDR-SOB). Neuroimaging included amyloid-β (Aβ) and tau positron emission tomography (PET), diffusion tensor imaging (DTI), vascular imaging, and resting-state functional MRI (rs-fMRI).ResultsAs expected, higher Aβ and tau burden were significantly associated with worse cognitive performance on the MMSE, ADAS-Cog, and CDR-SOB. Greater PTSD symptom severity was also linked to poorer cognition measured by all three tests, and higher TBI severity correlated with lower MMSE scores. However, neither TBI severity nor PTSD symptoms were associated with neuroimaging biomarkers of neurodegeneration or vascular damage.ConclusionsThese findings suggest that cognitive impairment in veterans is related to the prior history of TBI and PTSD, but these risk factors may not affect the cognition directly through the accumulation of AD pathologies or vascular injuries. Although these results need further validation by other cohorts who have more recent trauma and wider range of cognitive impairment.