Correlation of β2-microglobulin with postoperative delirium and 3-year mortality undergoing knee or hip replacement surgery: a prospective cohort study

Introduction: Postoperative delirium (POD) is a commonly occurring condition in the postoperative period. Therefore, the study intends to investigate the relationship between B₂M and POD and the effect of B₂M levels on three-year postoperative mortality in patients with POD. Methods: Postoperatively, the Confusion Assessment Method (CAM) and the Monumental Delirium Assessment Scale (MDAS) were used to assess the incidence and severity of POD. Preoperative plasma B₂M levels were measured utilizing a latex-enhanced immunoturbidimetric assay. Total tau protein (T-tau), phosphorylated tau protein (P-tau), and amyloid β plaque 42 (Aβ₄₂) were detected in preoperative cerebrospinal fluid (CSF) by enzyme-linked immunosorbent assay. Logistic regression equations were applied to examine the risk factors linked to POD. Patients presenting with POD were grouped according to B₂M level and followed up for 3 years postoperatively for their survival and Kaplan–Meier survival curves were plotted. Results: The prevalence of POD was 7.23%. Serum B₂M levels were higher in POD patients compared to non-POD (NPOD) patients (p = 0.01). The results of the logistic regression analysis indicated that B₂M (OR = 1.394, 95% CI = 1.017–1.910, p = 0.002) and T-tau (OR = 1.006, 95% CI = 1.002–1.011, p = 0.007) posed a risk for POD. B₂M and POD were partially associated through the mediation of CSF T-tau (10.0%). The K-M survival curves showed that patients with high B₂M who developed POD had a higher mortality rate 3 years after surgery (p = 0.031). Conclusion: In summary, B₂M may be a risk factor for POD, which might be mediated in part by CSF T-tau.