Hospital use, institutionalisation and mortality associated with delirium

Delirium is a disorder affecting consciousness, which gives rise to core clinical features and associated symptoms. Older patients are particularly prone, owing to higher rates of pre-existing cognitive impairment, frailty, co-morbidity and polypharmacy.

The aim of this study was to investigate the hypotheses that delirium affects the most vulnerable older adults and is associated with long-term adverse health outcome.

This prospective cohort study evaluated 278 medical patients aged > or = 75 years admitted acutely to a district general hospital in South Wales. Patients were screened for delirium at presentation and on alternate days throughout their hospital stay. Assessments also included illness severity, preadmission cognition, co-morbidity and functional status. Patients were followed for 5 years to determine rates of institutionalisation and mortality. Number of days in hospital in the 4 years prior to and 5 years after index admission were recorded.

Delirium was detected in 103 patients and excluded in 175. Median time to death was 162 days (interquartile range 21-556) for those with delirium compared with 1,444 days (25% mortality 435 days, 75% mortality>5 years) for those without (P < 0.001). After adjusting for multiple confounders, delirium was associated with an increased risk of death (hazard ratio range 2.0-3.5; P < or = 0.002). Institutionalisation was higher in the first year following delirium (P = 0.03). While those with delirium tended to be older with more preadmission cognitive impairment, greater functional dependency and more co-morbidity, they did not spend more days in hospital in the 4 years prior to index admission.

Delirium is associated with high rates of institutionalisation and an increased risk of death up to 5 years after index event. Prior to delirium, individuals seem to compensate for their vulnerability. The impact of delirium itself, directly or indirectly, may convert vulnerability into adverse outcome.