Prevalence, Incidence and Mortality of Delirium in Patients With COVID-19

A Systematic Review and Meta-analysis

Shih-Chieh Shao; Chien-Cheng Lai; Yi-Hung Chen; Yung-Chang Chen; Ming-Jui Hung; Shu-Chen Liao


Age Ageing. 2021;50(5):1445-1453. 

In This Article

Abstract and Introduction


Background: Attention should be paid to delirium in coronavirus disease 2019 (COVID-19) patients, especially older people, since advanced age poses increased risk of both delirium and COVID-19-related death.

Objective: This study aims to summarise the evidence on prevalence, incidence and mortality of delirium in COVID-19 patients.

Methods: We conducted a comprehensive literature search on Pubmed and Embase from inception to 1 December 2020. Three independent reviewers evaluated study eligibility and data extraction, and assessed study quality. Outcomes were analysed as proportions with 95% confidence interval (CI). We also compared mortality differences in COVID-19 patients using odds ratio.

Results: In total, we identified 48 studies with 11,553 COVID-19 patients from 13 countries. Pooled prevalence, incidence and mortality rates for delirium in COVID-19 patients were 24.3% (95% CI: 19.4–29.6%), 32.4% (95% CI: 20.8–45.2%) and 44.5% (95% CI: 36.1–53.0%), respectively. For patients aged over 65 years, prevalence, incidence and mortality rates for delirium in COVID-19 patients were 28.2% (95% CI: 23.5–33.1%), 25.2% (95% CI: 16.0–35.6%) and 48.4% (95% CI: 40.6–56.1%), respectively. For patients under 65 years, prevalence, incidence and mortality rates for delirium in COVID-19 patients were 15.7% (95% CI: 9.2–23.6%), 71.4% (95% CI: 58.5–82.7%) and 21.2% (95% CI: 15.4–27.6%), respectively. Overall, COVID-19 patients with delirium suffered higher risk of mortality, compared with those without delirium (OR: 3.2, 95% CI: 2.1–4.8).

Conclusion: Delirium developed in almost 1 out of 3 COVID-19 patients, and was associated with 3-fold overall mortality. Our findings suggest that first-line healthcare providers should systematically assess delirium and monitor related symptoms among COVID-19 patients.


Since the emergence of coronavirus 2019 (COVID-19) disease in China in December 2019, it has affected over 1.2 billion people worldwide, causing >2.7 million deaths up to 22 March 2021.[1] Among the different age groups, older people are at particular risk of developing or dying from COVID-19 infections, probably because of weaker immune response and frailty.[2–5] For example, mortality was found to be 6-times higher in patients with COVID-19 aged over 65 years old, compared with those younger than 65.[6,7] To date, only limited treatment options are available specifically for COVID-19,[8] so early identification and management of complications related to COVID-19 infections (e.g. venous thromboembolism, catheter-related bloodstream infections, pressure ulcers, falls and delirium) are critical to prevent mortality in the geriatric population.[9]

The increased neuropsychiatric complication risk in COVID-19 patients, especially in older people, may be on account of viral factors (e.g. direct central nervous system invasion and induction of central nervous system inflammatory mediators), treatment factors (e.g. medication, such as cortisone, analgesics and antibiotics, prolonged mechanical ventilation and deep sedation with immobilisation), disease factors (e.g. fever, dehydration and hypoxia) and environmental factors (e.g. isolation and separation from family;[10,11]). Among the various neuropsychiatric complications, delirium, a transient but reversible disturbance of consciousness and inattention triggered by an acute event (e.g. medical illness;[12]), is associated with an increased risk of adverse outcomes, such as longer stays in hospitals and death during admission.[13] Early studies indicate that 20–30% of COVID-19 patients will present with or develop delirium or mental status changes during the course of their hospitalisation, with rates of 60–70% in cases of severe illness.[14–16]

Understanding the epidemiological features of delirium and COVID-19 is an urgent research priority, especially in older people, where age increases the risk of both developing delirium and COVID-19-related death. Recently, there has been an increase in the volume of published literature on delirium in patients with COVID-19. Therefore, a comprehensive synthesis of existing evidence investigating prevalence, incidence and mortality of delirium in COVID-19 patients is necessary to inform clinical care and public health policy. Specifically, we aimed to identify mortality differences in COVID-19 patients with and without delirium.