In plain English
Delirium and dementia both produce confusion and cognitive impairment but are different conditions. Delirium is acute, fluctuating, and almost always caused by a treatable medical problem. Recognising it and treating the underlying cause is one of the most important tasks in geriatric medicine.
The fundamental difference
Delirium (ICD-11 6D70) is an acute confusional state developing over hours to days, with fluctuating attention and awareness, usually caused by an underlying medical problem. Dementia is a chronic, progressive cognitive impairment developing over months to years, with a stable underlying neurodegenerative or vascular disease.
Both can occur together: Delirium superimposed on dementia is extremely common in hospital admissions of older adults with dementia.
Side-by-side comparison
| Delirium | Dementia | |
|---|---|---|
| Onset | Hours to days | Months to years |
| Course | Fluctuating, often hour-to-hour | Stable or slowly progressive |
| Attention | Markedly impaired | Usually preserved early |
| Consciousness | Altered (drowsy or hyperalert) | Usually normal |
| Cause | Acute medical problem | Underlying brain disease |
| Reversibility | Often reversible with treatment | Not reversible |
| Urgency | Same-day medical review | Routine clinic referral |
How to recognise Delirium
The most useful clinical tool is the 4AT (4 'A's Test), a brief bedside assessment:
- Alertness: drowsy, agitated or normal;
- AMT4: age, date of birth, place, current year;
- Attention: months of the year backwards from December;
- Acute change or fluctuating course: evidence of significant change from baseline.
A score of 4 or more strongly suggests Delirium and warrants prompt medical review. The 4AT is used widely in UK acute hospitals and NHS 111 protocols.
Common causes of Delirium
The acronym PINCH-ME captures the commonest:
- Pain (often untreated);
- Infection (urinary tract, chest, skin);
- Nutrition and dehydration;
- Constipation;
- Hydration;
- Medication (new medicines, recent changes, anticholinergic burden, opiates);
- Environment (hospital admission, change of routine).
Less common but important causes include alcohol withdrawal, hypoglycaemia, stroke, intracranial haemorrhage, head injury and seizure activity.
What to do when Delirium is suspected
Delirium is a medical emergency. Same-day GP review, NHS 111, or 999 in severe cases. Investigations usually include blood tests, urine analysis, ECG, and where indicated chest X-ray and brain imaging.
Treatment is directed at the underlying cause. Supportive measures include reassurance, familiar people, good lighting, hearing aids and glasses, hydration, and avoiding medicines that worsen Delirium (benzodiazepines, anticholinergics, opiates where possible).
Delirium in someone with established dementia
People with dementia are particularly vulnerable to Delirium. The combination produces a sudden worsening of confusion, agitation or alertness in a person whose baseline is already impaired. The clinical clue is that the new behaviour is different from the person's usual pattern in dementia, with rapid onset over hours to days.
Common triggers are the same as Delirium without dementia: infection, pain, constipation, medication, dehydration. Same-day review and treatment of the underlying cause usually returns the person to their dementia baseline.
Outcome after Delirium
Most Delirium resolves with treatment of the underlying cause, often over days to a few weeks. However:
- An episode of Delirium increases future dementia risk;
- Some people have a persistent reduction in baseline cognitive function for weeks to months after a Delirium episode;
- Recurrent Delirium episodes accelerate cognitive decline in people with dementia.
This is the strongest argument for prompt recognition and treatment.
When to call urgently
- Sudden change in alertness or attention;
- New marked confusion in a person with dementia;
- New physical symptoms (fever, breathlessness, vomiting, pain);
- Acute behavioural change with safety risk.
NHS 111 or 999 in severe cases. Your GP for same-day review where less urgent.
Frequently asked questions
Can Delirium happen at home?
Yes. Delirium is most common in hospital settings but occurs commonly at home, particularly in older adults with infections, dehydration, medication issues or pain.
Will Delirium go away?
Most Delirium resolves with treatment of the underlying cause, often within days to a few weeks. Some people have a persistent reduction in baseline cognition.
Does Delirium cause dementia?
An episode of Delirium increases future dementia risk. Recurrent episodes accelerate decline in people with established dementia.
How can I prevent Delirium in someone with dementia?
Maintain hydration, treat infections promptly, avoid unnecessary medication changes, manage pain and constipation, keep familiar people and routines, and ensure hearing aids and glasses are in use.
Should I go to A&E?
If there is significant new confusion with physical symptoms (fever, breathlessness, severe pain) or safety risk, yes. Otherwise NHS 111 or same-day GP review is appropriate.
References
- World Health Organization. ICD-11 6D70 Delirium.
- NICE CG103: Delirium: prevention, diagnosis and management.
- Bellelli G et al. The 4AT: a screening tool for Delirium and cognitive impairment. Age and Ageing 2014.
- Inouye SK. Delirium in older persons. NEJM 2006.