Acute confusion: what is delirium and how does it differ from dementia?

My mother, who already has dementia, suddenly became much more confused than usual, seeing things and agitated, and it happened almost overnight. Is this the disease getting worse or is it something else?

That fear is understandable — such a rapid change frightens any carer. And it's important to know: confusion that appears suddenly is rarely "just the dementia getting worse". There is almost always a treatable cause behind it.

Why it happens

Delirium is a state of acute confusion that arises within hours or days. Unlike dementia, which evolves slowly over months and years, delirium is sudden and fluctuating (varying throughout the day). It is often triggered by infections (especially urinary and respiratory), dehydration, constipation, pain, fever, or medication. In people with dementia, it is even more common and requires rapid attention.

Practical strategies

• Suspect delirium whenever confusion suddenly worsens.
• Check for fever, pain, constipation, strong-smelling urine, or signs of dehydration.
• Maintain a calm environment, with adequate light and familiar faces.
• Ensure hydration and review recent medication.

What NOT to do

• Do not assume it is just the progression of dementia and wait to see.
• Do not argue or contradict hallucinations; reassure calmly.

When to seek professional help

Delirium is a situation that requires urgent assessment. Contact NHS 111, your GP, or A&E. Once the cause is treated, the confusion usually improves.

"Overnight my father didn't recognise me and saw people in the house. It was a urinary infection. With antibiotics, he returned to how he was." — Anonymous Carer