Delirium after surgery: a retrospective study of predictors, complications, and screening patterns in the national surgical quality improvement program

Background: Postoperative delirium is a serious yet underrecognized complication affecting diverse surgical populations, with profound implications for morbidity, mortality, and long-term cognitive function. Its prediction remains imprecise, and screening practices vary widely. Methods: We conducted a retrospective analysis of the 2021-2023 data from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP). The study included 217,783 adult surgical patients with documented delirium assessment. Patients were categorized as delirium, non-delirium, or unscreened, with an additional 2.7 million unscreened patients analyzed to assess selection bias in screening. The primary outcome was the incidence of delirium. Other outcomes included surgical and medical complications, mortality, length of stay, functional decline, discharge destination and conditions, and perioperative lab values. Multivariable regression models were used to identify independent predictors of delirium and its associated outcomes. Findings: Delirium screening was performed exclusively in patients aged ≥75 years, accounting for 7.3% of all surgical patients. Screening rates declined with advancing age (44% of patients aged 90+ vs 56% aged 75-79), while the proportion screening positive increased sharply (3.1% at 75-79 years vs 12.8% at ≥90 years). Delirium occurred in 10.6% (n = 23,100) of screened patients. Compared with non-delirium patients, those with delirium were older (mean 81.3 vs 79.9 years, p < 0.0001), more functionally dependent, and had higher ASA class and comorbidity burden. Dementia (37% vs 7.9%, p < 0.0001), recent falls (40% vs 18%, p < 0.0001), and urgent/emergency surgery (55% vs 26%, p < 0.0001) were strongly associated. Each 10-min increase in operative time was seen to independently be associated with 2.3% raised odds of delirium (p < 0.0001). Delirium was independently associated with higher 30-day mortality (OR 3.2, 95% CI 2.9-3.5), reoperation (OR 2.3, 95% CI 2.1-2.5), surgical complications (OR 1.8, 95% CI 1.6-1.9), loss of independence (OR 1.6, 95% CI 1.5-1.7), and reduced odds of home discharge (OR 0.5, 95% CI 0.4-0.5). Interpretation: Postoperative delirium is an independent predictor of adverse surgical outcomes yet remains substantially under-screened, with disparities across patient groups. These findings underscore the need for standardized, routine screening and targeted prevention strategies to improve perioperative care. Funding: No funding was received for this study.