The association between atherogenic index of plasma and postoperative delirium in cardiac surgery patients: an analysis of the MIMIC-IV database.

Abstract

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. Propensity score matching (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. Restricted cubic spline (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: AIP was independently and nonlinearly associated with an increased risk of POD following cardiac surgery. As an easily calculable composite lipid indicator, AIP may serve as a potential biomarker for preoperative risk stratification.