Delirium Shows Lower Mortality Than Other Encephalopathy Types in Critically Ill Patients: A Survival Analysis of 15,630 ICU Stays
Shankar Biswas1, Sindhu Vasireddy2, Elangovan Krishnan3, Yashasvi Srivastava1, Jeimy Marilyn Castellanos4
1Internal Medicine, Ivano-Frankivsk National medical university, 2Neurology, NMC Speciality Hospital, 3Immunology and microbiology, university of louisville, 4Internal Medicine, Universidad Autonoma del Estado de Quintana Roo
Objective:
To compare mortality across encephalopathy subtypes—delirium, toxic, metabolic, and unspecified—in ICU patients and assess independent predictors of survival using adjusted and subgroup analyses.
Additionally, to explore whether the lower mortality in delirium reflects its greater reversibility compared with other encephalopathy etiologies.
Background:
Different encephalopathy types in the ICU may have distinct prognoses, but comparative outcomes data are limited. We hypothesized that encephalopathy etiology influences mortality risk in critically ill patients.
Design/Methods:
Retrospective cohort study of 11,468 patients with encephalopathy across 15,630 ICU stays in MIMIC-IV. Patients were categorized into four encephalopathy types: delirium (32.4%), toxic (34.0%), metabolic (15.8%), and unspecified (17.9%). Primary outcome was all-cause mortality up to 1 year. We used Cox proportional hazards models adjusted for age, gender, severity, ICU type, and length of stay. Kaplan-Meier curves compared survival distributions. Subgroup analyses stratified outcomes by age, severity, and ICU type.
Results:
Overall mortality was 18.8% in-hospital, rising to 44.8% at 1 year. After adjustment, delirium showed a protective effect compared to unspecified encephalopathy (reference): hazard ratio 0.84 (95% CI 0.79-0.89, p<0.001), representing 16% lower mortality risk. Metabolic encephalopathy showed no significant difference: HR 1.05 (0.98-1.13, p=0.140). Toxic encephalopathy showed no significant difference: HR 0.98 (0.92-1.03, p=0.396). Unadjusted mortality rates were: delirium 49.2%, metabolic 59.1%, toxic 57.3%, unspecified 57.0%. The protective effect of delirium persisted across age groups, severity levels, and ICU types. Age (HR 1.01 per year, p<0.001) and high severity (HR 5.63, p<0.001) were the strongest mortality predictors.
Conclusions:
Delirium is associated with 16% lower mortality risk compared to other encephalopathy types in ICU patients, even after adjusting for severity and other confounders. This suggests delirium may be more reversible than metabolic or toxic encephalopathy, with important implications for prognostication and treatment strategies.
KEYWORDS: delirium, encephalopathy, mortality, prognosis, critical care, survival analysis
Disclaimer: Abstracts were not reviewed by Neurology® and do not reflect the views of Neurology® editors or staff.