Publication date: Jul 11, 2025

Delirium is a common complication in older patients hospitalized with COVID-19 and is associated with short-term functional and cognitive decline. This study evaluated whether in-hospital delirium is associated with long-term mortality and changes in frailty and cognition. This study is part of 2 retrospective and prospective Dutch multicenter cohort studies: the COVID-OLD and the CliniCo study. Patients aged ≥70 years who survived hospitalization for COVID-19 were included in this study. Patients were hospitalized during the first (March-May 2020) and second wave (September 2020-December 2020) of the COVID-19 pandemic. Follow-up data were collected by phone approximately 2 years after hospital discharge. In-hospital delirium was assessed using the Delirium Observation Screening Scale. Multivariable linear regression models were used to investigate the association between in-hospital delirium, and change in Clinical Frailty Scale, and change in cognition (Informant Questionnaire on Cognitive Decline in Elderly). Multivariable logistic regression models were used to investigate the association between in-hospital delirium and mortality at follow-up. At hospital discharge, 1663 patients were alive. Of those patients, 272 died before follow-up, 955 did not participate in the follow-up, and 436 patients participated in the follow-up. Of the follow-up cohort (median age, 75 years; interquartile range, 73-80; 65. 4% men), 14. 2% had in-hospital delirium. Delirium was not associated with long-term changes in Clinical Frailty Scale (β = 0. 36; 95% CI, -0. 11 to 0. 82) or with mortality (OR, 1. 29; 95% CI, 0. 80-2. 08). Patients with delirium more frequently suffered from long-term cognitive decline than patients without delirium (β = 2. 45; 95% CI, 1. 19-3. 71). Delirium was associated with long-term cognitive decline, but not with increased levels of frailty or mortality at follow-up. Follow-up consultations especially after delirium might be needed to assess possible cognitive decline.

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