Impact of hospital readmissions following hospitalisation with delirium on 12-month mortality: a quaternary Australian hospital experience.

Purpose: Inpatient delirium and unplanned hospital readmissions are associated with increased mortality. This study aimed to determine the effect of 28-day unplanned hospital readmissions on 12-month mortality post-discharge in patients with delirium during index hospitalisation.

Methods: Retrospective longitudinal cohort study of adults aged 65 or above with delirium during hospitalisation at a Victorian quaternary hospital was performed. Delirium was identified by the inclusion of ICD-10 (International Classification of Diseases, 10th revision) codes in the hospital medical discharge summary. Descriptive statistics was obtained for baseline characteristics. Cox proportional hazards model was developed to identify independent predictors of 12-month post-discharge mortality.

Results: One thousand six hundred thirty-four patients with delirium during in-patient admission were included. The overall 12-month mortality rate was 35% (572 patients). Of the 1,425 patients who survived their index admission, 11.2% had an unplanned 28-day readmission. In Cox regression analysis, unplanned readmission (hazard ratio (HR) 2.3, 95% confidence internal (CI) 1.7-2.9), older age (HR 1.38, CI 1.11-1.72), Charlson Comorbidity Index (HR 1.21, CI 1.17-1.27), and discharge to nursing home (HR 1.58, CI 1.23-2.02) were independent predictors of 12-month mortality. Readmitted patients with 12-month mortality were older, with higher rates of dementia, polypharmacy, and nursing home residence compared to readmitted patients who did not reach this endpoint.

Conclusion: Unplanned hospital readmission within 28 days of discharge is an independent predictor of 12-month mortality post in-hospital delirium admission. Admissions complicated by delirium and readmission episodes should instigate discussions regarding prognostication and goals of care. Greater research is required to minimise hospital readmission rates following discharge in this cohort.