Postoperative Delirium in Older Adults Undergoing Noncardiac Surgery.

Importance: Understanding the association of postoperative delirium with adverse outcomes and the hospital-level variation of postoperative delirium is important for efforts to improve perioperative brain health. Objective: To examine (1) the association of postoperative delirium with 30-day mortality and complications and (2) hospital-level variation in postoperative delirium. Design, Setting, and Participants: This retrospective cohort study examined hospitalizations among patients aged 65 years and older who underwent noncardiac surgery in US hospitals between January 1, 2017, and December 31, 2020. Data were analyzed between August 28, 2024, and April 10, 2025. Exposure: Postoperative delirium. Main Outcomes and Measures: The association of the composite of death and major complications with postoperative delirium was examined using multivariable logistic regression. Variability in the hospital incidence of postoperative delirium was evaluated using multilevel logistic regression analysis. Results: Among 5 530 054 inpatient admissions for major noncardiac surgery in 3169 hospitals, the mean (SD) patient age was 74.7 (7.0) years, and 3 161 054 admissions (57.2%) were of female patients. The incidence of postoperative delirium was 3.6% (197 921 admissions). Compared with patients without postoperative delirium, patients with postoperative delirium were more likely to experience death or major complications (adjusted OR [aOR], 3.47; 95% CI, 3.41-3.53; P < .001), 30-day mortality (aOR, 2.77; 95% CI, 2.71-2.83; P < .001), and nonhome discharges (aOR, 3.96; 95% CI, 3.88-4.04; P < .001). Controlling for patient characteristics, the odds of postoperative delirium were higher for patients undergoing surgery in hospitals with a higher rate of postoperative delirium compared with hospitals with lower rates of postoperative delirium (median OR, 1.53; 95% CI, 1.50-1.56). Conclusions and Relevance: In this national retrospective cohort study of more than 5.5 million hospitalizations, older individuals undergoing major noncardiac surgery who experienced postoperative delirium had 3.5-fold higher odds of death or major complications, 2.8-fold higher odds of death, and 4.0-fold higher odds of nonhome discharge. There was substantial variation in the hospital rate of postoperative delirium after accounting for patient risk, which suggests that this complication may be an appropriate target for hospital efforts to improve perioperative brain health, provided that delirium screening and coding accuracy are improved.