How is delirium different from dementia?

Delirium comes on suddenly, fluctuates over the course of a day, and is reversible if the underlying cause is treated. Dementia is gradual and progressive. A person with dementia can also develop delirium, which often makes their dementia look much worse during the episode.

Why do hospitals miss it?

Quiet delirium (the withdrawn, sleepy, less responsive kind) is much more common than agitated delirium and is much harder to notice in a busy ward. Family members notice because they know what 'awake but not himself' looks like. Staff who only met your dad yesterday do not have that baseline.

How is delirium different from dementia?

Delirium comes on suddenly, fluctuates over the course of a day, and is reversible if the underlying cause is treated. Dementia is gradual and progressive. A person with dementia can also develop delirium, which often makes their dementia look much worse during the episode.

Why do hospitals miss it?

Quiet delirium (the withdrawn, sleepy, less responsive kind) is much more common than agitated delirium and is much harder to notice in a busy ward. Family members notice because they know what 'awake but not himself' looks like. Staff who only met your dad yesterday do not have that baseline.

Spotting delirium in your dad while he is in the hospital

April 25, 2026 2 min read In progress

Hospital-acquired delirium is common in older adults, often missed in busy wards, and dangerous if left untreated. Family members frequently catch it first because they know what their dad is like when he is well. A guide for what to watch for and how to bring it to the team.

When you are reading this

Your dad woke up confused. Or he keeps falling asleep mid-sentence. Or he is sweet to the night nurse and angry at you. Or he was fine yesterday and is somewhere else today.

This may be delirium.

What delirium actually is

Delirium is an acute, fluctuating change in attention and awareness, often triggered by something else (an infection, a medication, a pain, a low oxygen level, a sleep-deprived ward). It is common in older adults during hospitalization. It is associated with longer stays, higher risk of long-term cognitive decline, and worse outcomes overall.

It is also reversible when the underlying cause is found and addressed.

What to watch for

The two flavors:

Hyperactive: agitation, restlessness, pulling at lines, trying to get out of bed
Hypoactive: withdrawn, sleepy, slow to respond, not engaging

Hypoactive is more common and more often missed. Both fluctuate over the day. The phrase “he was fine this morning” is not reassurance; it is the diagnostic feature.

Five questions worth taking with you

[Full guide coming. The questions worth taking to the bedside team:]

Has the team formally screened my dad for delirium today?
What are the most likely triggers given his current medications and labs?
Is there a non-pharmacologic delirium plan in place (sleep, mobility, family presence, hearing aids)?
Are any of his medications known to increase delirium risk in older adults?
What would change my dad’s plan if delirium got worse overnight?

Where I come in

If you describe what you are seeing, I will compare it to the literature on hospital-acquired delirium in older adults, surface the medications most often implicated, and help you frame the conversation with the team. Family observations are the most important data the team does not have. I will help you bring it.

Want me to read your dad's actual situation?

These guides are general. Your dad is not. Tell me what is happening and I will draft questions specific to him.

Tell me about your dad