Why the difference matters
When someone living with dementia becomes more confused in the evening, it's natural to assume it's sundowning. Often it is. But understanding sundowning vs. delirium is one of the most important safety skills a family caregiver can have, because delirium can look very similar and it needs medical attention.
Delirium usually has a physical cause, such as an infection or a medication, and treating that cause is how it gets better. Missing it can mean a treatable illness goes untreated.
The key difference: a pattern vs. a sudden change
Sundowning is a pattern. It repeats, most evenings, in a way you've probably come to recognize. Your loved one may be restless or anxious as the light fades but is more or less their usual self at other times of day.
Delirium is a change. It's a sudden shift in mental function that comes on over hours or days. The person is suddenly more confused, more agitated, or much sleepier than their normal, and the change doesn't go away in the morning, though it may come and go.
The question to ask yourself is simple: "Is this new, or different from their usual?" If the answer is yes, think delirium first.
Sundowning vs. delirium at a glance
| Sundowning | Delirium |
|---|---|
| Develops gradually and becomes a familiar pattern | Comes on suddenly, over hours or days |
| Happens around the same time most days, usually late afternoon or evening | Can happen at any time, and symptoms often come and go through the day and night |
| More or less their usual self earlier in the day | Clearly different from their usual self, even in the morning |
| Restless, anxious, or agitated | May be agitated, or unusually sleepy, withdrawn, and hard to engage |
| Linked to dementia-related brain changes, tiredness, and the environment | Usually triggered by a physical cause such as infection, dehydration, or medication |
| Eased by routine, light, calm, and reassurance | Needs a medical assessment to find and treat the cause |
| Not an emergency on its own | A medical emergency |
What is delirium?
Delirium, sometimes called an acute confusional state, is a sudden change in the way the brain is working. It affects thinking, memory, awareness, and especially attention. NHS inform describes it as one of the most common medical emergencies, and older adults and people with dementia are at higher risk.
Delirium doesn't always look like agitation. Doctors describe three main types:
- Hyperactive: restless, agitated, disoriented, sometimes seeing things that aren't there. This type is the easiest to confuse with sundowning.
- Hypoactive: slowed down, very sleepy, withdrawn, and less responsive. This quiet type is easy to miss, because the person may simply seem tired.
- Mixed: switching between the two.
What causes sudden confusion in the elderly?
Delirium is usually triggered by something happening in the body, and often by more than one thing at once. Common triggers include:
- Infections, especially urinary tract infections (UTIs) and chest infections such as pneumonia.
- Dehydration, or not eating and drinking enough.
- Medications: a new medicine, a change in dose, an interaction, or stopping a medicine suddenly.
- Pain, which your loved one may not be able to describe.
- Constipation.
- Surgery, or a stay in the hospital.
- Injuries, such as a fall or a hip fracture.
- Low blood sugar in people with diabetes.
- Alcohol withdrawal, or severe stress and lack of sleep.
UTI confusion in the elderly
UTIs deserve a special mention. In older, frail adults, a UTI may not cause the familiar burning or urgency at all. The NHS lists changes in behavior, such as acting agitated or confused, along with incontinence that's worse than usual and new shivering, as possible signs of a UTI in this group. Only a clinician can diagnose a UTI, so don't try to treat it at home. Ask for your loved one to be checked.
Warning signs it may be delirium, not sundowning
- Confusion that is suddenly worse than their usual, over hours or a few days.
- Trouble paying attention: they can't follow a simple conversation or keep track of what you're saying.
- Unusual drowsiness, being hard to wake, or staring and not engaging.
- Symptoms that don't settle by morning, or that come and go through the day.
- New hallucinations, suspicion, or fearfulness that isn't typical for them.
- A sudden change in sleep, such as being awake all night and asleep all day.
- Physical signs such as fever, shivering, new incontinence, not eating or drinking, or signs of pain.
- A recent new medication, illness, fall, or hospital stay.
You know your loved one's normal better than anyone. Relatives and carers are often the first to notice delirium, so trust your instinct if something feels different.
What to do if you suspect delirium
Keep them safe and stay with them
Stay close, speak calmly in short, simple sentences, and reassure them. Avoid firing lots of questions at them, and don't restrain them unless they're in danger.
Get medical help the same day
Call their doctor or after-hours line and say clearly: "I think this could be delirium. This is a sudden change from their normal." If you can't reach anyone, or they seem seriously unwell, go to the emergency room or call 911.
Describe their usual self
Clinicians who don't know your loved one may assume the confusion is just dementia. Explain what they're normally like and exactly what has changed and when.
Bring the essentials
Take a list of all medications and supplements, including any recent changes, plus their glasses, hearing aids, and dentures.
Help them feel oriented
Having someone they know well nearby, a visible clock or calendar, and a few familiar things like family photos can help someone with delirium feel less frightened. Offer food and drinks if it's safe to do so.
The same gentle communication that helps with sundowning helps here too. See how to talk to someone with dementia. Tools built for everyday sundowning, such as Hamton, can offer comfort in a familiar voice, but they are never a substitute for medical care when delirium is possible.
When to seek urgent care
Sudden new confusion should always be assessed promptly, and the NHS advises emergency care when someone suddenly becomes confused. Call 911 if your loved one:
- Is very drowsy, hard to wake, or unresponsive.
- Has slurred speech, trouble speaking, facial drooping, or weakness on one side of the body.
- Has had a fall or a head injury.
- Has a seizure.
- Has chest pain or difficulty breathing.
- Has a high fever or is shivering and confused.
- Has diabetes and may have low blood sugar.
Recovery after delirium
Most delirium improves once the cause is found and treated, often within a few days. For some people it lasts weeks or even months, and people living with dementia may not fully return to how they were before. Be patient with the recovery and with yourself.
Once things settle, go back to what helps day to day: a steady routine, daylight, and a calm evening. Our guides to preventing sundowning and how to calm sundowning can help you rebuild. Watching for the next sudden change is also one of the best protections you have. And a health scare like this takes a toll on caregivers, so see our guide to caregiver burnout.
Frequently asked questions
How can I tell if it's sundowning or delirium?
Sundowning is a familiar pattern that repeats around the same time most days. Delirium is a sudden change from the person's usual self over hours or days, often with poor attention or unusual drowsiness. If it's new or different, get medical advice the same day.
Can a UTI cause sudden confusion in the elderly?
Yes. In older, frail adults, a urinary tract infection may show up as new agitation or confusion rather than the usual urinary symptoms. A doctor can check for infection and treat it.
Is delirium a medical emergency?
Yes. Delirium is considered a medical emergency because it's usually caused by an underlying illness that needs treatment. Sudden confusion should be assessed by a doctor promptly.
Can someone with dementia have delirium?
Yes, and people with dementia are much more likely to develop it. Because delirium can be worse in the evening, it's easily mistaken for sundowning, so look for a sudden change from their usual pattern.
How long does delirium last?
Most delirium lasts a few days once the cause is treated, but it can persist for weeks or even months. Some people, especially those living with dementia, may not fully return to how they were before.
Sources
- NHS inform — Delirium
- NHS — Sudden confusion (delirium)
- NHS — Urinary tract infections (UTIs)
- MedlinePlus (U.S. National Library of Medicine) — Delirium
- Cleveland Clinic — Delirium
This guide is for general information and support. It is not medical advice and does not replace guidance from a doctor or care team. If someone is in danger, contact emergency services. Read our editorial policy to see how guides are researched and updated.
