A pandemic of delirium: an updated systematic review and meta-analysis of occurrence of delirium in older adults with COVID-19

Purpose Delirium has been recognized as an atypical presenting feature of COVID-19 in older adults and is independently associated with mortality. We aimed to perform an updated systematic review of the literature and proportional meta-analysis to assess prevalence and incidence of delirium in older adults with COVID-19, addressing differences according to sex, frailty status, and settings. Methods We searched databases for English-language articles on prevalence and incidence of delirium in older adults with COVID-19, published between March 2020 and January 2023. Results Of the 1171 articles identified, 66 met selection criteria and were included in the meta-analysis (n = 35,035 participants, age-range 66-90 years old, 46.6% females). We observed similar pooled prevalence (20.6% [95% Confidence Interval (CI) 17.8-23.8%]) and incidence (21.3% [95% CI 14.7-30%]) of delirium. Pooled occurrence (both prevalence and incidence) of delirium was similar according to sex (females 21.3% [95% CI 16-27.5%] vs. males 23.8%% [95% CI 18.2-30.4%], p-value = 0.55) and study setting (nursing homes 22.5% [95% CI 14.2-33.6%] vs. hospital 20.3% [95% CI 17-24%], p = 0.68), but it was significantly higher in frail versus non-frail patients (37% [95% CI 26.6-48.8%] vs. 12.5% [95% CI 7.8-19.6%], p-value < 0.01). Delirium definitions and assessment tools largely varied across studies. Conclusion This review delineates delirium as a common feature of COVID-19, particularly in frail older adults, and supports its formal inclusion among COVID-19 symptoms. The considerable heterogeneity in delirium assessment highlights the need for an operational strategy to standardize definitions and tools utilization in the management of frail older adults.