Postoperative delirium in hip fracture patients linked to epigenetic alterations in inflammatory and immune pathways: a genome-wide DNA methylation study

Delirium is a common yet underdiagnosed condition in elderly hospitalized patients. The lack of effective diagnostic and therapeutic methods can be attributed to the limited understanding of its pathophysiology. Delirium has recently been reported to be linked to neuroinflammation and epigenetic changes. The aim of this study was to validate the pathways in a larger cohort with a uniform type of surgery, while rigorously adjusting for potential covariates. This study primarily investigated DNA methylation (DNAm) changes before and after surgery in postoperative delirium (POD) among older adults having undergone femoral fracture surgery. After propensity analysis, 65 subjects were divided into 2 subgroups; one consisted of subjects who had blood samples collected preoperatively and on postoperative day 0, and the other consisted of those who had samples collected preoperatively and on postoperative day 3. We performed differential methylation analysis and enrichment analysis on each subgroup. Enrichment analysis using CpGs that exhibited substantial DNAm changes between pre- and postoperative day 0 samples in POD cases showed inflammation- and immunity-related pathways such as "leukocyte mediated immunity" and "NF-kappa B signaling pathway." Inflammation- and immunity-related pathways became less noticeable between pre- and postoperative day 3 samples. Inflammation- and immunity-related pathways showed in this study align with previous studies across diverse populations, reinforcing the role of inflammation- and immunity-related epigenetic mechanisms in delirium including POD. Notably, these DNAm changes were potentially transient, corresponding to the typical onset of delirium, suggesting their potential as biomarkers for early diagnosis.