The DECIDE Study: Delirium and Cognitive Impact in Dementia

Abstract

Background: Delirium is a severe neuropsychiatric syndrome of brain dysfunction precipitated by acute illness and characterised by acute and fluctuating inattention and other cognitive and perceptual deficits. Delirium is common, distressing and associated with poor outcomes. Previous studies examining the impact of delirium on cognitive trajectories have been limited by incomplete ascertainment of baseline cognition or a lack of prospective delirium assessments. The DECIDE study aimed to explore the association between delirium and cognitive function over time in participants in an existing population-based cohort aged 65 years and older with known baseline cognition. Methods: Over a 12-month period, surviving participants from the Cognitive Function and Ageing Study II-Newcastle were screened for delirium on admission to hospital. Baseline characteristics along with disease relevant clinical parameters were recorded. The progression/resolution of delirium was monitored. In those with and without delirium, cognitive decline and dementia was assessed at one-year follow-up. The effect of delirium on cognitive function over time was evaluated, independent of baseline cognition and illness severity, along with the predictive value of clinical parameters. Results: 82 of 205 participants developed delirium in hospital during the study period (40%). 18 of the 135 participants completing one-year follow-up interviews received a new diagnosis of dementia. Delirium was associated with an increased risk of new dementia diagnosis at follow up, independent of illness severity and baseline cognition (OR 8.76 [CI: 1.85 – 41.37], p=0.006). More than 5 days of delirium and more severe delirium were independently associated with worse cognitive outcomes. Conclusions: An episode of delirium whilst in hospital significantly increases risk of future cognitive decline and dementia, independent of illness severity and baseline cognition. Given that delirium has been shown to be preventable in around a third of cases, it can be proposed that delirium is a potentially modifiable risk factor for dementia.