The prevalence and risk factors for delirium in older patients hospitalized with COVID-19

By Dr. Liji Thomas, MDReviewed by Danielle Ellis, B.Sc.Aug 31 2022

The coronavirus disease 2019 (COVID-19) pandemic took a high toll on the elderly population worldwide compared to younger individuals. The features of the illness in very old and frail patients appeared to be more severe and often different compared to those in younger age groups. The reasons for this difference in presentation remain obscure.

Background

A recent study published in Geriatric Psychiatry explored what determined the risk of delirium in older patients hospitalized with COVID-19 and the outcomes of this hospitalization. The study, carried out as part of the multicenter COVID-OLD cohort study, looked at patients aged 60 years and above.

Introduction

One in seven and almost one in two patients have been reported to develop delirium when hospitalized with COVID-19 in the general ward. Older and frailer people more often develop this feature, which often serves as a marker of severe disease.

Hospitalized patients have been known to be at a higher risk of delirium if dementia and/or cognitive impairment are present if they are very old, require help with the activities of daily living, have a prior history of delirium or other illnesses. The role of frailty as an independent determinant of delirium risk in COVID-19 is not yet established.

The approximately 400 patients in this study were hospitalized in the Netherlands between February and May 2020. All were admitted to the general ward, the median age being 76 years. The prevalence of delirium during this time was obtained from the recorded Delirium Observation Screening Scale (DOSS), applied three times daily. If the results were above the specified cut-off, a clinical assessment was made by the ward physician as well.

The researchers also looked at the length of hospitalization, as well as discharge to home or nursing facilities, and in-hospital deaths.

Frailty, as measured by the Clinical Frailty Scale (CFS), has been used to predict in-hospital mortality in older patients hospitalized with COVID-19. Delirium in this age group is also thought to be a predictor of increased illness and mortality risk. The question is whether the increased risk of mortality with delirium is due to the fact that these patients are also frailer deserves to be explored.

What did the study show?

The researchers found that 82 of this group of patients developed delirium during their episode of hospitalization – that is, about one in five patients. A prior episode of delirium was associated with almost 10-fold higher odds of developing delirium this time around, while a history of memory issues posed nearly the same level of risk.

The researchers also found that patients with delirium had a more acute course of illness, with a shorter period of symptoms before presenting to the hospital. Their C-reactive protein (CRP) levels were lower at the time of presentation. However, vital signs did not differ significantly from those of non-delirium patients.

On average, patients with delirium stayed in hospital for longer periods, and more often required nursing care on discharge, as seen by their discharge destination. While one in seven patients without delirium required further stay in a long-term care facility, this occurred in one in three patients who developed delirium.

However, no significant increase in the risk of death was noted in association with delirium. This was even though more than a quarter of the cohort died in hospital. This outcome was reported for almost half the patients in delirium but about one in five patients without delirium.

The risk factors for mortality included advanced age and increased frailty, but not delirium.

Conclusions

The study identified a previous history of delirium and pre-existing memory issues as determinants of a higher risk of delirium during the current episode of COVID-19 meriting hospitalization. However, delirium was not associated with higher mortality risk, independent of frailty.

These findings contrast with some other studies, reflecting the need for more research to understand how well frailty explains the higher risk of death following hospitalization for COVID-19 in the elderly compared with others. “These findings seem to suggest that predisposing delirium risk factors, e.g. a previous delirium, are more important than precipitating delirium risk factors, e.g. disease severity at presentation, for delirium risk in COVID-19 patients.”

This shows how important it is to assess the risk of delirium by screening for its risk factors in this patient subgroup. This could help provide preventive measures, which have been shown to mitigate the risk of delirium among at-risk patients by 40%. It would also help ensure early treatment, which cuts short its severity and duration.