The key clinical features used to differentiate delirium from other causes of acute confusion in older adults primarily involve the **recent onset** (within hours or days) and **fluctuating nature** of symptoms NICE CG103. These changes may be reported by the person at risk, or a carer or relative NICE CG103.
- Cognitive function: Indicators include worsened concentration, slow responses, and confusion NICE CG103.
- Perception: Changes may involve visual or auditory hallucinations NICE CG103.
- Physical function: Features can include reduced mobility, reduced movement, restlessness, agitation, changes in appetite, and sleep disturbance NICE CG103.
- Social behaviour: This may manifest as difficulty engaging with or following requests, withdrawal, or alterations in communication, mood, and/or attitude NICE CG103.
It is particularly important to be vigilant for changes that may indicate **hypoactive delirium**, which are often missed, such as withdrawal, slow responses, reduced mobility and movement, worsened concentration, and reduced appetite NICE CG103. While it can be difficult to distinguish between delirium, delirium superimposed on dementia, or dementia alone, clinical guidelines advise managing delirium first due to its nature as a reversible and serious acute illness NICE CKS,NICE CG103.