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Clinical Review State of the Art Review

Delirium and long term cognition in critically ill patients

BMJ 2021; 373 doi: (Published 08 June 2021) Cite this as: BMJ 2021;373:n1007
  1. M Elizabeth Wilcox, associate professor1 2,
  2. Timothy D Girard, associate professor3,
  3. Catherine L Hough, professor4
  1. 1Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, ON, Canada
  2. 2Division of Respirology, Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, ON, Canada
  3. 3Clinical Research, Investigation, and Systems Modeling of Acute illness (CRISMA) Center, Department of Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
  4. 4Division of Pulmonary and Critical Care Medicine, Oregon Health & Science University, Portland, OR, USA
  1. Correspondence to: M E Wilcox elizabeth.wilcox{at}


Delirium, a form of acute brain dysfunction, is very common in the critically ill adult patient population. Although its pathophysiology is poorly understood, multiple factors associated with delirium have been identified, many of which are coincident with critical illness. To date, no drug or non-drug treatments have been shown to improve outcomes in patients with delirium. Clinical trials have provided a limited understanding of the contributions of multiple triggers and processes of intensive care unit (ICU) acquired delirium, making identification of therapies difficult. Delirium is independently associated with poor long term outcomes, including persistent cognitive impairment. A longer duration of delirium is associated with worse long term cognition after adjustment for age, education, pre-existing cognitive function, severity of illness, and exposure to sedatives. Interestingly, differences in prevalence are seen between ICU survivor populations, with survivors of acute respiratory distress syndrome experiencing higher rates of cognitive impairment at early follow-up compared with mixed ICU survivor populations. Although cognitive performance improves over time for some ICU survivors, impairment is persistent in others. Studies have so far been unable to identify patients at higher risk of long term cognitive impairment; this is an active area of scientific investigation.


  • Series explanation: State of the Art Reviews are commissioned on the basis of their relevance to academics and specialists in the US and internationally. For this reason they are written predominantly by US authors

  • Contributors: MEW wrote the first draft of the manuscript. TDG and CLH edited the document. All authors approved the final version. MEW is the guarantor.

  • Competing interests: We have read and understood the BMJ policy on declaration of interests and declare the following: none.

  • Provenance and peer review: Commissioned; externally peer reviewed.

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