Impact of oral frailty on postoperative delirium in older patients undergoing off-pump coronary artery bypass grafting: a prospective observational study

Postoperative delirium (POD) is a frequent and serious complication after cardiac surgery. Although oral frailty has been associated with cognitive decline and systemic inflammation, its role in POD after cardiac surgery remains unclear. This study aimed to investigate the association between preoperative oral frailty and POD in older patients undergoing off-pump coronary artery bypass grafting (OPCABG). In this prospective observational study, 289 consecutive patients aged ≥ 60 years who underwent OPCABG between July 2024 and October 2025 were enrolled. Preoperative oral function was assessed using the Oral Frailty Index-8 (OFI-8), with oral frailty defined as a score ≥ 4. POD was evaluated on postoperative days 1–7 using the Confusion Assessment Method (CAM) and CAM-ICU. Multivariable logistic regression was performed to identify independent predictors. The discriminative performance of the multivariable model incorporating oral frailty was assessed using receiver operating characteristic (ROC) analysis, and mediation analysis was used to explore the indirect role of preoperative cognitive function. POD occurred in 116 patients (40.1%). After adjustment for confounders, advanced age ( OR 1.075, 95% CI 1.014–1.739, p = 0.015), oral frailty (OR 2.103, 95% CI 1.204–3.673, p = 0.009), diabetes mellitus (OR 1.797, 95% CI 1.052–3.017, p = 0.032), and preoperative MoCA score (OR 0.931, 95% CI 0.867–0.999, p = 0.041) were independently associated with POD. The multivariable model incorporating oral frailty demonstrated moderate discrimination (AUC 0.711, 95% CI 0.650–0.771) and good calibration (Hosmer–Lemeshow p = 0.843), with a sensitivity of 75.9% and specificity of 58.4%. Mediation analysis indicated that preoperative cognitive function accounted for only 1% of the indirect effect of oral frailty on POD ( p = 0.176). Preoperative oral frailty is independently associated with POD in older patients undergoing OPCABG. Although its discriminative ability is moderate, oral frailty screening may serve as a feasible and cost-effective adjunctive tool for perioperative risk stratification and targeted delirium-prevention strategies.