Incidence and interaction factors of delirium as an independent risk of mortality in elderly patients in the intensive units: a retrospective analysis from MIMIC-IV database

Background: As delirium is a common problem in critcal elderly patients, the aim of the study was to investigate the interaction factors of delirium as an independent risk of mortality in elderly patients in the intensive care unit (ICU). Patients and methods: Elderly patients (age ≥ 65) were selected from Medical Information Mart for Intensive Care (MIMIC)-IV database. Demographics data were collected on the 1st day of admission to ICU. The main outcome is in-hospital mortality. Propensity score matching analysis (PSMA) was used to remove the influence of comfounding factors between survival and nonsurvival groups. Chi-square test and logistic regression analysis was used to identify the association between delirium and in-hospital death. Stratified analysis and interaction analysis was used to evaluate the interaction factors of delirium as a risk of in-hospital mortality. Results: 22,361 patients were selected, and in which 2809 patients died. 5453 patients had delirium (about 24.4%). There is a significant difference in delirium between the survival and nonsurvival groups before and after PSMA (p = 0.000 and p = 0.030). Logistic regression showed delirium, sequential organ failure assessment (SOFA), and hemoglobin were all significantly related to in-hospital death (p = 0.000). SOFA score and hemoglobin concentration were proved to be remarkable interaction factors of delirium (p = 0.000, and p = 0.041). Significant correlation between delirium and hospital mortality was inhibited when SOFA was more than 12 or hemoglobin was higher than 15 g/dL. In-hospital mortality (49.1% vs. 10.5%, p = 0.000) and shock incidence (87.9% vs. 15.8%, p = 0.000) of the patients with SOFA ≥ 12 was much higher than that of the patients with SOFA ≤ 11. Conclusion: SOFA and hemoglobin are interaction factors of delirium as an independent risk of in-hospital mortality in elderly patients in the intensive care unit.