Aim: Delirium is a common presenting symptom among older patients. Patients who presented with delirium may have a higher morbidity and mortality rate due to older age, other comorbidities, and atypical COVID-19 presentation. Currently, the evidence supporting delirium as one of the predictors of poor outcome of COVID-19 is still insufficient. This study aims to explore the potential association between delirium and poor outcomes from COVID-19.

Methods: We systematically searched the PubMed and Google Scholar databases using specific keywords related to our aims until January 30th, 2021. All articles published on COVID-19 and delirium were retrieved. The quality of the study was assessed using the Newcastle Ottawa Scale (NOS) tool for observational studies and Joanna Briggs Institute (JBI) Critical Appraisal Tools for case-series studies. Statistical analysis was done using Review Manager 5.4 software.

Results: Our meta-analysis of 20 studies showed that delirium symptoms on admission was associated with poor outcomes from COVID-19 [OR 2.36 (95% CI 1.80-3.09), p < 0.00001, I(2) = 76%, random-effect models] and its subgroup which consist of severe COVID-19 [OR 3.89 (95% CI 1.72-8.75), p = 0.001, I(2) = 91%, random-effect models], and mortality from COVID-19 [OR 1.90 (95% CI 1.55-2.33), p < 0.00001, I(2) = 36%, random-effect models]. Meta-regression showed that the association was influenced by age (p = 0.005).

Conclusions: Our study suggests delirium as an important marker to identify patients at higher risk for developing poor COVID-19 outcomes. The physicians should add delirium as one of the common presenting symptoms of COVID-19 in older populations.