ICU-Delirium Linked to Reduced Long-Term Survival, Particularly in Older Patients, Study Reveals

"Out of 9,600 ICU survivors, 22.6% developed delirium during their stay. These patients showed a significantly lower survival rate up to four years post-discharge compared to those without delirium, " the researchers reported. They noted that the effect was most evident in patients aged 55 and older, particularly those over 65. Additional analyses confirmed that ICU delirium is an independent predictor of reduced long-term survival.

Delirium, a common but often underrecognized condition in ICU settings, is characterized by acute confusion, agitation, and fluctuating levels of consciousness. It is typically associated with a range of critical illnesses, including infections, organ failure, or prolonged sedation. Previous research has established a correlation between ICU delirium and short-term complications, but the impact on long-term survival has remained unclear—until now.

To fill this knowledge gap, Giovanna Brandi, Institute for Intensive Care Medicine, University Hospital Zurich, University of Zurich, Zurich, Switzerland, and colleagues conducted a retrospective single-center observational study at the Institute of Intensive Care Medicine at the University Hospital Zurich, Switzerland.

All adult ICU survivors from four years were screened for eligibility. ICU delirium was defined using the Intensive Care Delirium Screening Checklist (ICDSC) and the F05 diagnosis code from the ICD-2019. ICU survivors who developed delirium (group D) were compared to those who did not (group ND). Survival was tracked using hospital electronic health records up to four years post-ICU discharge. Kaplan-Meier curves and absolute risk differences (ARD) were used for survival analysis. A multivariable logistic regression model was applied, with long-term survival at four years as the primary outcome, considering clinical conditions and interventions associated with survival. Subgroup analysis categorized ICU survivors by age (45–54, 55–64, ≥ 65 years) and relevant clinical conditions.

The study led to the following findings:

• 9,604 patients met the inclusion criteria, of whom 22.6% (2,171) developed ICU delirium.
• Patients in the ICU-delirium group (group D) had a significantly lower survival probability compared to those in the non-delirium group (group ND) (ARD = 11.8%).
• In the multivariable analysis, ICU delirium was independently associated with reduced long-term survival.
• Among patients aged 55–64 years, those in the ICU-delirium group were less likely to survive at all time points up to four years post-ICU discharge compared to the non-delirium group (ARD = 7.3%).
• This survival difference was even more significant in patients over 65 years (ARD = 11.1%).
• There were no significant survival differences in other age groups.

"The study found that ICU delirium is independently associated with reduced long-term survival. Patients who developed delirium during their ICU stay experienced lower survival rates up to four years after discharge, with this association being particularly pronounced in those over 55 years of age," the researchers concluded.

Reference:

De Trizio, I., Komninou, M.A., Ernst, J. et al. Delirium at the intensive care unit and long-term survival: a retrospective study. BMC Neurol 25, 22 (2025). https://doi.org/10.1186/s12883-025-04025-7