No significant associations between history of head injury and Alzheimer's disease fluid biomarkers in older adults

BackgroundConcussions are gaining attention as a risk factor for Alzheimer's disease (AD). Previous reports suggest concussion, also called head injury (HI), may be associated with changes to AD biomarkers, including amyloid and tau. However, there has been little characterization of biofluid biomarkers in older adults with remote history of HI.ObjectiveWe investigated whether aging participants at risk for AD with self-reported HI history would demonstrate alterations to cerebrospinal fluid (CSF) and blood plasma biomarkers of AD.MethodsUsing two-way ANCOVAs and linear mixed effects models, we examined both baseline cross-sectional and longitudinal associations between HI history, cognition, and AD biofluid biomarkers in 100 participants with HI history compared to 2411 without HI history from the ADNI dataset.ResultsOn baseline analysis, participants with HI history had higher CSF Aβ_42/40 ratios than non-HI participants. There were no other baseline differences in biomarkers between HI and non-HI participants, nor were there any main effects of HI upon longitudinal analysis. We observed consistent main effects of age and cognitive impairment that suggested a pattern of worsened AD biomarker signatures in impaired participants with increasing age.ConclusionsOur findings do not support an association between self-reported HI history and AD fluid biomarkers in older adults from the ADNI dataset. Further characterization of fluid biomarker trajectories both in the acute post-HI period and in participants with remote HI is needed to understand the temporal dynamics of fluid biomarkers after HI and the implications of HI for AD risk.