Efficacy of Bundle Interventions for the Prevention of Delirium in the Intensive Care Unit: An Umbrella Meta‐Analysis of Randomised Clinical Trials and Cohort Studies

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Background Delirium is a common and serious complication in ICU patients, leading to prolonged ICU length of stay (LOS), increased mechanical ventilation (MV) duration and higher mortality. The ABCDEF bundle has been proposed to prevent or reduce ICU delirium, but the strength and consistency of evidence across existing meta‐analyses remain unclear. Aim This umbrella meta‐analysis aimed to evaluate the pooled effects of ABCDEF bundle interventions on ICU delirium incidence and duration, with secondary objectives assessing their impact on ICU LOS, MV duration, ICU mortality and in‐hospital mortality. Study Design A comprehensive search was conducted across Web of Science, PubMed, EMBASE, Cochrane Reviews, Google Scholar, CNKI, Weipu and Wanfang up to May 2025. Meta‐analyses of RCTs and cohort studies were included if they assessed interventions incorporating at least three components of the ABCDEF bundle and reported ICU‐related outcomes. Methodological quality was assessed using the AMSTAR 2 tool; four meta‐analyses rated as critically low quality were excluded. Six meta‐analyses were included in the final synthesis. The certainty of evidence for each outcome was evaluated using the GRADE approach. Results A total of 4534 records were identified, of which six meta‐analyses met the inclusion criteria, encompassing 62,949 participants. Three meta‐analyses demonstrated a significant 50% reduction in ICU delirium incidence (OR = 0.50; 95% CI: 0.39–0.65; p < 0.001; I 2 = 0%). Two meta‐analyses showed a significant reduction in delirium duration (SMD = −1.39; 95% CI: −2.38 to −0.40; p = 0.006; I 2 = 0%). ICU mortality was not significantly reduced (OR = 0.71; 95% CI: 0.33–1.53; p = 0.384; I 2 = 64.2%), but a 19% reduction in in‐hospital mortality was observed in three meta‐analyses (OR = 0.81; 95% CI: 0.71–0.93; p < 0.01; I 2 = 23.4%). Four meta‐analyses reported shorter ICU LOS (SMD = −0.89; 95% CI: −1.65 to −0.13; p = 0.021; I 2 = 81.8%), and three reported reduced MV duration (SMD = −0.55; 95% CI: −1.08 to −0.02; p = 0.043; I 2 = 65.4%). Conclusions This umbrella meta‐analysis provides moderate to high‐certainty evidence supporting the efficacy of bundle interventions in reducing ICU delirium incidence and improving clinical outcomes, including ICU LOS and MV duration. While heterogeneity was noted in some outcomes, ABCDEF bundled approaches remain a promising strategy for improving the care of critically ill patients. Relevance to Clinical Practice This umbrella review highlights the importance for critical care nurses to select and implement at least three ABCDEF bundle components, based on individual patient needs, to reduce ICU delirium and improve recovery outcomes.