Plasma and MRI biomarkers capture neuronal damage in former professional boxers.

Repetitive Head Impacts (RHI) in boxing may increase the risk for neuronal damage. We evaluated blood-based biomarkers for neurodegeneration and Alzheimer's Disease (AD) pathology, clinical features, and MRI biomarkers in former professional boxers compared to patients with AD or patients with subjective cognitive decline (SCD). Nine former boxers were compared to age-matched patients (without single TBI or RHI) with biomarker confirmed AD (N = 15) or SCD (N = 14). Plasma samples were analyzed for amyloid beta (Aβ)42, Aβ42/40 ratio, phosphorylated tau (p-tau)181, p-tau217, glial fibrillary acidic protein (GFAP) and neurofilament light (NfL) concentrations. Brain MRI images were processed through Freesurfer to compute disease-related regions-of-interest (ROIs) for AD, frontotemporal dementia (FTD), or chronic traumatic encephalopathy (CTE). Cognitive performance was assessed in memory and executive functioning (EF) domains. Five boxers had follow-up measurements after ~ 7 years. Former boxers had higher plasma GFAP, p-tau181 and p-tau217 than patients with SCD, lower volumes in all pre-specified disease-related brain regions. No differences on neuropsychological test scores between boxers and those with SCD were observed. Longitudinal analysis in the boxer group demonstrated elevation of plasma NfL and p-tau181 over time. The current study suggests the presence of biological processes indicative for neurodegeneration in former boxers, without evident clinical decline. Plasma GFAP, p-tau181 and p-tau217 may be promising biomarkers for indicating risk for neuronal damage following RHI.