Differences in 90-day mortality of delirium subtypes in the intensive care unit: A retrospective cohort study.

INTRODUCTION: Many intensive care unit (ICU) patients suffer from delirium which is associated with deleterious short-term and long-term effects, including mortality. We determined the association between different delirium subtypes and 90-day mortality. MATERIALS AND METHODS: Retrospective cohort study in ICU patients admitted in 2015-2017. Delirium, including its subtypes, was determined using the confusion assessment method-ICU (CAM-ICU) and Richmond agitation sedation scale (RASS). Exclusion criteria were insufficient assessments and persistent coma. Cox-regression analysis was used to determine associations of delirium subtypes with 90-day mortality, including relevant covariates (APACHE-IV, length of ICU stay and mechanical ventilation). RESULTS: 7362 ICU patients were eligible of whom 6323 (86%) were included. Delirium occurred in 1600 (25%) patients (stratified for delirium subtype: N = 571-36% mixed, N = 485-30% rapidly reversible, N = 433-27% hypoactive, N = 111-7% hyperactive). The crude hazard ratio (HR) for overall prevalent delirium with 90-day mortality was 2.84 (95%CI: 2.32-3.49), and the adjusted HR 1.29 (95%CI: 1.01-1.65). The adjusted HR for 90-day mortality was 1.57 (95%CI: 1.51-2.14) for the mixed subtype, 1.40 (95%CI: 0.71-2.73) for hyperactive, 1.31 (95%CI: 0.93-1.84) for hypoactive and 0.95 (95%CI: 0.64-1.42) for rapidly reversible delirium. CONCLUSION: After adjusting for covariates, including competing risk factors, only the mixed delirium subtype was significantly associated with 90-day mortality.