Delirium and post-discharge dementia: results from a cohort of older adults without baseline cognitive impairment

Objectives: to investigate the association between delirium occurrence in acutely ill older adults and incident dementia after hospital discharge. Methods: retrospective cohort study examining acutely ill older adults aged +60 years and consecutively admitted to the geriatric ward of a tertiary university hospital from 2010 to 2016. Inclusion criteria were absence of baseline cognitive decline on admission and documented clinical follow-up of +12 months after discharge. Admission data were collected from our local database, including results from a standardized comprehensive geriatric assessment completed for every patient. Pre-existing cognitive decline was identified based on clinical history, CDR and IQCODE-16. Delirium was diagnosed using short-CAM criteria, while post-discharge dementia after 12 months was identified based on medical records' review. We used competing-risk proportional-hazard models to explore the association between delirium and post-discharge dementia. Results: we included 309 patients. Mean age was 78 years, and 186 (60%) were women. Delirium was detected in 66 (21%) cases. After a median follow-up of 24 months, 21 (32%) patients who had experienced delirium progressed with dementia, while only 38 (16%) of those without delirium had the same outcome (P=0.003). After adjusting for possible confounders, delirium was independently associated with post-discharge dementia with a sub-hazard ratio of 1.94 (95%CI=1.10-3.44; P=0.022). Conclusion: one in three acutely ill older adults who experienced delirium in the hospital developed post-discharge dementia during follow-up. Further understanding of delirium as an independent and potentially preventable risk factor for cognitive decline emphasizes the importance of systematic initiatives to fight it.