The Prevalence of Frailty in Critically Ill Patients: A Systematic Review and Meta-analysis

Abstract Rationale: Frailty, a state of reduced physiological reserve, increases vulnerability to adverse outcomes in critically ill patients. Prior systematic reviews have identified a high prevalence of frailty in the critically ill. Given the growing number of studies reporting on frailty in critically ill patients, the objective of this systematic review and meta-analysis was to comprehensively examine the prevalence of frailty in critically ill populations. Methods: We conducted this review according to the Meta-analysis of Observational Studies in Epidemiology (MOOSE), and the PRISMA guidelines and pre-registered on Prospero (CRD42023473646). We searched MEDLINE, EMBASE, CINAHL, ClinicalTrials.gov, and the Cochrane Library up to October 23, 2023. We included observational studies and randomized controlled trials (RCTs) reporting the prevalence of frailty in adult critically ill populations from any type of ICU, as defined by validated frailty tools. Abstracts and reviews were excluded. Two independent reviewers screened citations and abstracted data in duplicate. We performed subgroup analysis based on the frailty instrument used and the type of critical care unit. We used R software for analysis, and pooled data using random-effects models. Results: We included 92 reports encompassing 90 separate studies and 102 frailty analyses of over 266,000 frail patients and 927,000 non-frail patients. The aggregated prevalence of frailty across all studies was 28% (95% confidence interval [CI]: 26%-31%) (Figure 1). Subgroup analyses by ICU type demonstrated prevalence of frailty to be 28% (95% CI: 25%-31%) in general medical surgical ICUs and 33% (95% CI: 24%-42%) in cardiac ICUs. Frailty prevalence by frailty instrument was 28% (95% CI: 25%-31%) when assessed with the Clinical Frailty Scale, 37% (95% CI: 27%-49%) when assessed with the Frailty Index, 32% (95% CI: 24%-42%) when assessed with the Frailty Phenotype, 22% (95% CI: 12%-37%) when assessed with the Modified Frailty Index-11 and 28% (95% CI: 13%-50%) when assessed with the Modified Frailty Index-5. Conclusions: The prevalence of frailty varies among critically ill patients with point estimates ranging from 22-37% depending on the frailty instrument used for ascertainment and the type of critical care unit. The high prevalence of frailty in critically ill populations likely reflects reduced physiological reserve underpinning frailty predisposing to critical illness. Future research should focus on standardizing assessments. Funding: The Canadian Frailty Network