A full examination should be performed to search for evidence of underlying causes of the confusion and a 4AT [7] should be completed.

Distinguishing between delirium, dementia and primary psychiatric illness can be challenging as neuropsychiatric symptoms such as psychosis and depression often co-exist in patients with dementia. NICE recommends that if there is difficulty distinguishing between them, to manage the delirium first.

The following table may help with the differentiation between them.

Table 1 Distinguishing features between delirium, dementia, and psychosis [6]

Characteristic Delirium Dementia Psychosis
Onset Acute Gradual Variable
Course Fluctuating Progressive* Chronic
Diminished level of consciousness May be present (hypoactive/mixed delirium) Absent Absent
Orientation Fluctuating Impaired Normal
Duration Hours to months Months to years Months to years
Hallucinations Common Rare until end stage Common
Attention Impaired Preserved until end stage May be Impaired
Sleep-wake pattern Disrupted Normal or fragmented Variable

*Exception: fluctuations in cognition are present in Lewy body dementia.