Association between ICU delirium burden and long-term cognitive outcomes following discharge: a systematic review and meta-analysis stratified by follow-up time

Background Delirium burden during critical illness may be associated with long-term cognitive impairment in intensive care unit survivors. However, the magnitude and time-course of this association remain uncertain. Methods We conducted a systematic review and meta-analysis of adult ICU survivors. PubMed, Embase, Scopus, Web of Science, the Cochrane Library, and China National Knowledge Infrastructure were searched from inception to 20 January 2026. Eligible studies measured delirium burden during the ICU or hospital stay and assessed cognition at least 3 months after discharge. Effect estimates were converted to Pearson correlation coefficients and pooled with restricted maximum-likelihood random-effects models using Knapp-Hartung adjustment. Results Ten studies were included, and six contributed to quantitative synthesis (k  = 6; N = 1,137). Greater delirium burden was associated with worse long-term cognition (pooled r  = − 0.133, 95% confidence interval (CI) − 0.225 to − 0.039; p  = 0.015), with negligible heterogeneity ( I² = 0.1%) and a negative 95% prediction interval (− 0.23 to − 0.03). In studies with follow-up of 12 months or less, the pooled correlation remained significant ( r  = − 0.13, 95% CI − 0.19 to − 0.06). In contrast, the numerically stronger association beyond 12 months should be interpreted with caution, as only two studies were available. Sensitivity analyses did not materially change the direction or significance of the pooled estimate, and four qualitative studies were directionally consistent. Conclusions A greater delirium burden is associated with poorer long-term cognitive outcomes in ICU survivors. These findings support intensified delirium prevention, systematic measurement of delirium burden, and targeted post-PICS cognitive follow-up.