A prospective pilot study on plasma amyloid beta oligomers and postoperative delirium.

Introduction: Postoperative delirium (POD) is common in older adults and has been linked to Alzheimer's disease (AD). Plasma amyloid-β oligomers (AβOs) may clarify this relationship. We evaluated whether preoperative AβO burden is associated with POD severity. Methods: In this single-center prospective pilot study, we enrolled 22 patients aged ≥65 years undergoing hip or knee arthroplasty under general anesthesia. Blood was drawn preoperatively and postoperatively to quantify oligomerized amyloid-β using the multimer detection system (MDS-Oaβ). POD was assessed with the Korean version of the Delirium Rating Scale-98 (K-DRS-98). Group comparisons and correlations examined associations between MDS-Oaβ and POD. Results: Eleven of 22 patients developed POD. Those with POD were older and had higher preoperative MDS-Oaβ than those without POD (0.81 vs 0.56 ng/mL). There was no significant perioperative change in MDS-Oaβ, suggesting surgery or anesthesia did not alter the plasma Aβ oligomerization tendency. Within the POD group, preoperative MDS-Oaβ correlated with both K-DRS-98 severity and total scores. Discussion: In this pilot cohort, higher preoperative AβO burden was associated with the occurrence and severity of POD, while perioperative factors did not measurably affect AβO levels. These findings support a potential mechanistic link between AD-related pathology and POD. Given the small sample (