# Plasma Glial Fibrillary Acidic Protein and p-Tau217: Potential Biomarkers of Delirium in Older Adults

## TL;DR

This study explores whether blood levels of two proteins, GFAP and p-Tau217, can predict delirium in older adults after surgery.

## Contribution

The study is the first to investigate plasma GFAP and p-Tau217 as potential biomarkers for delirium in older surgical patients.

## Key findings

- Higher plasma GFAP levels were linked to increased delirium incidence and severity.
- p-Tau217 was associated only with delirium severity, not incidence.
- GFAP appears to be a stronger biomarker for delirium risk than p-Tau217.

## Abstract

Delirium is a common complication of hospitalization among older adults, and is associated with cognitive decline, but the underlying mechanisms are poorly understood. Delirium and dementia are closely interrelated; therefore, blood biomarkers for Alzheimer’s disease (AD) and neural injury may yield insight to potential mechanisms in delirium.

Data were obtained from the Successful Aging after Elective Surgery (SAGES) study (n = 530). Glial fibrillary acidic protein (GFAP), a marker of reactive astrocytosis elevated in neurodegeneration and neural injury, and tau phosphorylated at residue 217 (p-Tau217), a marker of AD pathology, were measured from plasma collected prior to surgery. Post-operative delirium incidence and severity were assessed using the Confusion Assessment Method (CAM) and CAM-S (0-19, 19 worst), respectively.

Higher GFAP (4th vs. 1st quartile) was associated with delirium incidence (relative risk (RR) 1.7, 95% confidence interval (CI): 1.1-2.8) and greater CAM-S severity (adjusted mean difference=0.5, 95% CI: 0.1-1.0). p-Tau217 did not significantly predict delirium incidence, though higher levels were associated with greater severity (adjusted mean CAM-S difference 1st to 4th quartile=0.6, 95% CI: 0.1-1.0).

High pre-operative plasma GFAP was associated with higher delirium incidence and severity, whereas high p-Tau217 was associated only with higher severity. Overall, GFAP appears to be a stronger risk marker than p-Tau217 for delirium. Further work is needed to establish whether astrocytosis contributes to delirium pathophysiology.