Prognosis
There is substantial evidence that delirium results in long-term poor outcomes in older persons admitted to hospital. This systematic review only included studies that looked for an independent effect of delirium (i.e., after accounting for other associations with poor outcomes, for example co-morbidity or illness severity).
In older persons admitted to hospital, individuals experiencing delirium are twice as likely to die than those who do not (meta-analysis of 12 studies). In the only prospective study conducted in the general population, older persons reporting delirium also showed higher mortality (60% increase).
Institutionalisation was also twice as likely after an admission with delirium (meta-analysis of 7 studies). In a community-based population examining individuals after an episode of severe infection (though not specifically delirium), these persons acquired more functional limitations (i.e. required more assistance with their care needs) than those not experiencing infection. After an episode of delirium in the general population, functional dependence increased threefold.
The association between delirium and dementia is complex. The systematic review estimated a 13-fold increase in dementia after delirium (meta-analysis of 2 studies). However, it is difficult to be certain that this is accurate because the population admitted to hospital includes persons with undiagnosed dementia (i.e. the dementia was present before the delirium, rather than caused by it). In prospective studies, people hospitalised from any cause appear to be at greater risk of dementia and faster trajectories of cognitive decline, but these studies did not specifically look at delirium. In the only population-based prospective study of delirium, older persons had an eight-fold increase in dementia and faster cognitive decline. The same association is also evident in persons already diagnosed with Alzheimer’s dementia.
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