The impact of frailty on the outcomes of COVID-19 patients with persistent critical illness: A population-based cohort study

Objectives Persistent critical illness (PerCI, ≥10 days in Intensive Care Unit [ICU]) is defined as the time from ICU admission when patients’ antecedent characteristics define their mortality rather than the admission aetiology. Patients with frailty and without COVID-19 have a higher risk of developing and dying from PerCI. We aimed to investigate the impact of frailty on critically ill patients with COVID-19 experiencing PerCI. Methods We conducted a retrospective multicentre cohort study including 103 Australian and New Zealand ICUs over two years, investigating the impact of frailty, measured with Clinical Frailty Scale (CFS), in patients with COVID-19, between patients with and without PerCI. Results The prevalence of PerCI was similar between patients with and without frailty (25.4% vs. 27.9%; p=0.44). Hospital mortality was higher in patients with PerCI than without (28.8% vs. 9.3%; p<0.001), with mortality rising with increasing CFS (p<0.001). Frailty independently predicted hospital mortality, but when adjusted for ANZROD and sex, its impact was no different in patients with and without PerCI (odds ratio [OR]=1.30 [95%-CI: 1.14-1.49] vs. OR=1.46 [95%-CI: 1.29-1.64]). Conclusions The presence of frailty independently predicted hospital mortality in patients with PerCI, but frailty did not have a different impact on patients with and without PerCI. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: -All experimental protocols were approved by The Alfred Hospital Ethics Committee (Project No: 176/21) approved this study with a waiver of informed consent. -ANZICS Centre for Outcome and Resource Evaluation Management Committee granted access to the ANZICS-APD in accordance with standing protocols. -All methods were carried out in accordance with the relevant guidelines and regulations of the Declaration of Helsinki. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors