Preclinical Amyloid-β and Axonal Degeneration Pathology in Delirium

Background: The clinical relevance of brain beta-amyloidosis in older adults without dementia is not established. As delirium and dementia are strongly related, studies on patients with delirium may give pathophysiological clues. Objective: To determine whether the Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers amyloid-beta 1-42 (A beta(42)), total tau (T-tau), and phosphorylated tau (P-tau) are associated with delirium in hip fracture patients with and without dementia. Methods: CSF was collected in conjunction to spinal anesthesia in 129 patients. Delirium was assessed using the Confusion Assessment Method once daily in all patients, both pre-and postoperatively. The diagnosis of dementia at admission was based upon clinical consensus. CSF levels of A beta(42), T-tau, and P-tau were analyzed. Results: In patients without dementia, we found lower CSF A beta(42) levels (median, 310 ng/L versus 489 ng/L, p = 0.006), higher T-tau levels (median, 505 ng/L versus 351 ng/L, p = 0.02), but no change in P-tau in patients who developed delirium (n = 16) compared to those who remained lucid (n = 49). Delirious patients also had lower ratios of A beta(42) to T-tau (p < 0.001) and P-tau (p = 0.001) relative to those without delirium. CSF A beta(42) and T-tau remained significantly associated with delirium status in adjusted analyses. In patients with dementia, CSF biomarker levels did not differ between those with (n = 54) and without delirium (n = 10). Conclusion: The reduction in CSF A beta(42), indicating beta-amyloidosis, and increase in T-tau, indicating neurodegeneration, in hip fracture patients without dementia developing delirium indicates that preclinical AD brain pathology is clinically relevant and possibly plays a role in delirium pathophysiology.