Delirium vs. Dementia: Recognizing an Acute Change

An older patient who was talking with you earlier is now unusually quiet and struggles to follow a simple question. A dementia diagnosis appears in the chart. That history matters, but it does not explain away a new change.

Delirium and dementia can occur together. The bedside task is to recognize what is different, assess the person’s current condition, and communicate promptly so the cause can be evaluated.

Start with the timeline

Delirium typically develops over hours or days and can fluctuate. Changes in attention, awareness, thinking, activity, or sleep may be present. Dementia usually involves a more persistent decline over a longer period. Those patterns guide assessment; they do not allow a nurse to diagnose the cause from one conversation.

NICE delirium guidance highlights recent changes and warns that hypoactive delirium, including withdrawal or reduced movement, may be missed. Quiet behavior deserves attention as much as agitation.

Find out what is usual for this person

Ask the patient, people they identify as supporters, and the previous team about baseline function. Use specific questions: “Could they follow a conversation yesterday?” or “Is needing repeated prompts new?” A description is more useful than “normally confused.”

Check whether hearing aids, glasses, a familiar language, or an interpreter are needed. Difficulty hearing a question is not the same as inattention. Include those supports before drawing conclusions about a response.

Assess the change and escalate

Assess immediate clinical concerns, including airway, breathing, circulation, vital signs and other checks indicated by the presentation and local protocol. A sudden neurological deficit, reduced consciousness, or acute deterioration requires the appropriate emergency response. Do not wait for a screening score before seeking help.

NICE recommends the 4AT when delirium indicators are identified, with assessment by a competent practitioner; critical care and postoperative recovery use different recommended tools. Use the tool adopted for your setting and your training. Screening supports clinical evaluation rather than replacing it.

Give a concrete report

Compare a vague statement with a fictional example. “The patient seems off” leaves the listener to guess what changed. A clearer report might be:

“At 14:00 they answered questions in full sentences. At 16:10 they needed repeated prompts and could not stay with the conversation. Their supporter says this is new. I have assessed them and am concerned about an acute change.”

Add the actual assessment findings, relevant medications or events, and the response requested. Do not invent a cause such as infection because it is familiar. Several causes may need evaluation.

Support orientation while the cause is evaluated

Introduce yourself, explain where the person is, and speak calmly in short sentences. Offer appropriate sensory aids and involve a familiar supporter when the person wishes. Review comfort, sleep disruption, hydration needs and other contributors with the team, respecting restrictions and the care plan.

If a person is distressed, explain actions before approaching and allow time for a response. Describe observable behavior instead of labels such as “difficult.” Medication or restraint decisions require their own clinical assessment and institutional process.

Document fluctuation, not just a label

Record when the change was first noticed, the source of baseline information, specific observations, assessment results, who was notified and what happened next. If the person improves later, document that too. Fluctuation does not make the earlier concern irrelevant.

At handoff, state what remains uncertain and what follow-up has been arranged. The next nurse should know both the current presentation and the meaningful change that prompted review.