Impact of pre-admission functional status on intensive care patient outcomes: a systematic review and meta-analysis

BACKGROUND: Pre-admission functional status might be associated with mortality in critically ill patients admitted to the ICU. With this systematic review, we aimed to investigate the association of pre-admission functional domains with mortality after ICU admission and which functional measures were used. METHODS: We searched PubMed, Embase, and the Cochrane Register of Controlled Trials for studies of acutely admitted adult ICU patients reporting pre-admission functional status and mortality. Exploratory outcomes were mechanical ventilation, renal replacement therapy, delirium, ICU and hospital length of stay, discharge destination, and health-related quality of life. Screening, data extraction, and risk-of-bias evaluation were performed in duplicate. Certainty of evidence was assessed using Grading of Recommendations Assessment, Development, and Evaluation. RESULTS: Of the 55 observational studies included, 21 contributed to the meta-analyses. Overall, 26.7% of the participants were deceased at variable follow-up (ICU to 1 yr). Frailty prevalence ranged from 3.6% to 76.8%, and functional dependency from 10.6% to 68.7%. Meta-analysis showed a risk ratio (RR) of 0.62 (95% confidence interval [CI] 0.58-0.67, P<0.01) for all-cause mortality between non-frail and frail participants and an RR of 0.47 (95% CI 0.40-0.54, P<0.01) between independent and dependent participants. No statistically significant association was found in the subgroup analysis of exploratory outcomes. Statistical and clinical heterogeneity were substantial, and overall certainty of evidence was very low. CONCLUSIONS: Pre-admission frailty and functional dependency were associated with higher mortality after ICU admission. Overall, the evidence is very uncertain, and the true effect could differ substantially from our estimates.