Delirium is a common, life-threatening complication of critical illness that places patients at risk for negative clinical outcomes and increased health resource utilization following an intensive care unit (ICU) admission, according to study results published in the American Journal of Respiratory and Critical Care Medicine.

Delirium is common in the ICU and can lead to worse outcomes; however, its effect on mortality after hospital discharge and health resource utilization is not well understood. Therefore, researchers in Alberta, Canada, conducted a population-based, propensity-score matched, retrospective cohort study to estimate mortality and health resource utilization 2.5 years after hospital discharge in critically ill patients admitted to the ICU from January 1, 2014, to June 30, 2016. Delirium was measured by the 8-point Intensive Care Delirium Screening Checklist. The primary outcome was mortality, and the secondary outcome was a composite measure of subsequent emergency department visits, hospital readmission, or mortality.

In this study, 5936 propensity score matched patients with and without incident delirium who survived to hospital discharge. Delirium was associated with increased mortality at 0 through 30 days after discharge. There was no significant difference in mortality more than 30 days post-hospital discharge (delirium: 3.9% vs no delirium: 2.6%), and there was a persistent increased risk of emergency department visits, hospital readmissions, or mortality post-hospital discharge throughout the study period. At 2.5 years, 23.0% of patients who had experienced delirium during their ICU stay had died vs 20.9% of patients who had not experienced delirium.

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Similar to previous research, the study authors found patients with delirium experienced an increased length of stay in the ICU and hospital. More than $17,000 per patient has been reported as the 30-day cumulative cost associated with ICU delirium attributed to increased health care utilization. According to the authors, this finding implies that the long-term burden of delirium is not only costly to the patient, but the overall health care system.

“Our findings suggest that when examining the outcomes of ICU delirium for research or quality improvement purposes, follow-up for mortality to 30-days post-hospital discharge is likely sufficient. However, longer periods of follow-up are needed when also examining emergency department visits and hospital readmissions,” they concluded.


Fiest KM, Soo A, Lee CH, et al. Long-term outcomes in intensive care unit patients with delirium: a population-based cohort study. Am J Respir Crit Care Med. Published online April 6, 2021. doi:10.1164/rccm.202002-0320OC