Mild Traumatic Brain Injury Is Related to Elevated Cerebrospinal Fluid Tau in Alzheimer's Disease Dementia

A preliminary study on plasma markers across cognitive stages and links to a history of mild traumatic brain injury

Potential implications of a history of mild traumatic brain injury (mTBI) during aging are understudied. Seven plasma markers were measured in matched participants having normal cognition, mild cognitive impairment (MCI) and dementia of the Alzheimer's type (DAT) with and without a history of mTBI. Phosphorylated tau181 showed a moderate effect size for being greater in mTBI + individuals having MCI and DAT, and effect sizes for lower amyloid-β 42/40 and higher neurofilament light were seen for mTBI + DAT individuals. This preliminary report shows a potential role of plasma-derived markers in detecting associations between mTBI history and the development of Alzheimer's disease and related disorders.

Blood Markers in Relation to a History of Traumatic Brain Injury Across Stages of Cognitive Impairment in a Diverse Cohort

BACKGROUND

Traumatic brain injury (TBI) has been linked to multiple pathophysiological processes that could increase risk for Alzheimer's disease and related dementias (ADRD). However, the impact of prior TBI on blood biomarkers for ADRD remains unknown.

OBJECTIVE

Using cross-sectional data, we assessed whether a history of TBI influences serum biomarkers in a diverse cohort (approximately 50% Hispanic) with normal cognition, mild cognitive impairment, or dementia.

METHODS

Levels of glial fibrillary acidic protein (GFAP), neurofilament light (NFL), total tau (T-tau), and ubiquitin carboxy-terminal hydrolase-L1 (UCHL1) were measured for participants across the cognitive spectrum. Participants were categorized based on presence and absence of a history of TBI with loss of consciousness, and study samples were derived through case-control matching. Multivariable general linear models compared concentrations of biomarkers in relation to a history of TBI and smoothing splines modelled biomarkers non-linearly in the cognitively impaired groups as a function of time since symptom onset.

RESULTS

Each biomarker was higher across stages of cognitive impairment, characterized by clinical diagnosis and Mini-Mental State Examination performance, but these associations were not influenced by a history of TBI. However, modelling biomarkers in relation to duration of cognitive symptoms for ADRD showed differences by history of TBI, with only GFAP and UCHL1 being elevated.

CONCLUSIONS

Serum GFAP, NFL, T-tau, and UCHL1 were higher across stages of cognitive impairment in this diverse clinical cohort, regardless of TBI history, though longitudinal investigation of the timing, order, and trajectory of the biomarkers in relation to prior TBI is warranted.