The Association Between Atherogenic Index of Plasma and Postoperative Delirium in Cardiac Surgery Patients: An Analysis of the MIMIC-IV Database

Background This study aimed to investigate the relationship between the Atherogenic Index of Plasma (AIP) and the risk of Postoperative Delirium (POD) in patients undergoing cardiac surgery. Methods A retrospective cohort study was conducted using data from the MIMIC-IV 2.2 with patients who underwent cardiac surgery. AIP was calculated as log₁₀(TG/HDL-C). PSM was used in a 1:1 ratio to balance baseline characteristics (age, sex, race) between delirium and non-delirium groups. Multivariable logistic regression models were employed to assess the independent association between AIP (analyzed as both a continuous and categorical variable in quartiles) and POD, with adjustments for demographics, comorbidities, laboratory parameters, vital signs, medication use, and surgical details. RCS were used to explore nonlinearity. Subgroup and mediation analyses were also performed. Results Among 6,067 eligible patients, 1,565 (25.8%) developed POD. After PSM, 3,130 patients were analyzed. Multivariable regression revealed a significant positive association between AIP and POD (OR: 1.622, 95% CI: 1.455–1.81, P  < 0.001). Quartile stratification revealed that higher AIP levels were associated with an increased risk of POD (OR: 1.708, 95% CI: 1.399–2.088, P  < 0.001). In the fully adjusted model (Model 3), AIP remained significantly associated with POD (OR: 1.435, 95% CI: 1.249–1.652, P  < 0.001). RCS analysis revealed a significant nonlinear relationship between AIP and POD ( P  < 0.001), consistent across gender subgroups. Subgroup analysis revealed no significant interactions. Mediation analysis indicated that hemoglobin (Hb), red cell distribution width (RDW), albumin (Alb), and respiratory rate (RR) partially mediated the association between AIP and POD. Conclusion A higher AIP is independently associated with an increased risk of POD in patients undergoing cardiac surgery, exhibiting a nonlinear relationship. This association is partially mediated by several metabolic and inflammatory markers. AIP may serve as a valuable and easily obtainable predictive biomarker for POD risk stratification in this patient population.