Impact of self‐reported history of head injury on Alzheimer’s disease biomarker profiles

Abstract

AbstractBackgroundHead injury (HI) as a risk factor for Alzheimer’s disease (AD) has been attracting increased attention thanks to the discovery that concussion is linked to earlier and more severe development of AD (1). HI is prevalent, and a better understanding of how it contributes to AD risk and prognosis is necessary (2). Previous cross‐sectional studies have provided evidence of differences in biomarker levels between individuals with a history of HI and those without (2); this study investigates the effects of a history of HI on longitudinal patterns of AD biomarkers to better understand how HI affects AD risk.MethodUsing the Alzheimer’s Disease Neuroimaging Initiative (ADNI) dataset, we examined longitudinal levels of amyloid β (Aβ), phosphorylated tau (p‐tau), and total tau (t‐tau) in the cerebrospinal fluid (CSF) of 100 individuals with a history of HI and 100 non‐HI controls demographically‐matched on age, sex, race, ethnicity, and years of education. We also analyzed longitudinal levels of blood plasma free plasma (FP) 42, total plasma (TP) 42, pTau181, and NFL.ResultIndividuals with a history of HI had lower CSF Aβ at baseline, lower plasma TP42 at a month 48 follow‐up visit, and lower plasma pTau181 at 72‐ and 96‐month follow‐up visits. There were no differences between the groups on CSF p‐tau or t‐tau levels or plasma FP42 or NFL at any time point.ConclusionLower CSF and plasma amyloid in the HI group may indicate individuals with a history of HI have higher amyloid deposition, given the inverse correlation between CSF/plasma amyloid levels and amyloid deposition on PET (3). The unexpectedly lower plasma pTau in the HI group warrants further analysis. Some of our analyses may be underpowered, as underreporting of HI incidence in ADNI reduces the number of available HI participants. However, despite these limitations, we were able to find significant differences in some biomarkers in individuals with a history of HI. Future studies in expanded samples are needed.1. Fleminger et al. (2003). Journal of Neurology, Neurosurgery & Psychiatry 2. Small et al. (2013). The American Journal of Geriatric Psychiatry 3. Fagan et al. (2006). Annals of Neurology