Delirium vs dementia: the difference every family should know

Your mother came home from hip surgery on Wednesday. By Friday she was asking where her own mother was, talking to the dog in sentences that didn't make sense and falling asleep at noon. Someone at the hospital mentioned dementia. You spent the night thinking this was the new normal.

It may not be. When an older adult becomes confused suddenly, delirium vs dementia is the question that matters most, because the two have very different futures. Dementia is slow and progressive. Delirium is sudden, serious and often treatable. This guide explains how to tell them apart and what families can do.

What delirium is, and why it gets mistaken for dementia

Delirium is a sudden disturbance in attention and awareness, brought on by an illness, a medication, surgery or another stress on the body. It's very common in older adults in the hospital. The American Geriatrics Society calls it the most common complication after surgery in older adults.

It gets mistaken for dementia because on the surface they look alike: a person who is confused, forgetful and not themselves. The two also overlap. People with dementia are especially prone to delirium, and Mayo Clinic points out that dementia shouldn't be diagnosed during an episode of delirium, because the tests won't be accurate.

Three ways to tell them apart

How fast it started

Dementia builds over months and years. The forgetfulness comes first, then missed appointments, then lost words. By the time a family is worried, they can look back over a year or two of small changes. Delirium develops over hours or days. The mother who made her own coffee on Sunday isn't making sense on Tuesday.

What is being lost

Early dementia is mainly a problem of memory and language. The person usually knows where they are and can follow a conversation, even if they can't remember breakfast. Delirium is mainly a problem of attention. The person can't hold a thread. They look past you, drift mid-sentence, and can't stay with a simple question.

Whether it changes through the day

Dementia is fairly steady from hour to hour. Delirium comes and goes. Someone may seem nearly themselves at 10 a.m. and not recognize their own bedroom by 4 p.m. Doctors say delirium waxes and wanes. When families hear that phrase, the pattern often makes sense at last.

The quiet kind is the one that gets missed

Most people picture delirium as agitation: pulling at an IV, shouting, seeing things. That's hyperactive delirium, and it's hard to miss.

In older adults, the more common form is hypoactive delirium, and it's quiet. The person sleeps much more than usual, answers in a word or two, and seems far away. Families assume Mom is tired from surgery. The chart says she had a restful day. Because nothing looks alarming, it often isn't caught. Some people swing between the two forms in the same day, agitated at night and barely responsive in the morning.

What sets delirium off

The list of triggers is long, and that's good news in a way: each one can be looked for and treated.

• Infection. Pneumonia and urinary tract infections often show up in older adults as confusion before anything else.
• Medications. Sleep aids, opioids, benzodiazepines, some bladder medicines, and the antihistamine in Benadryl and many nighttime cold remedies are common culprits. So is a new prescription from the hospital.
• Surgery and the hospital itself. Anesthesia, broken sleep, a noisy room that's never fully dark, missing glasses and hearing aids, and being kept in bed.
• Body chemistry. Dehydration, low sodium, low blood sugar, low oxygen and thyroid trouble.
• Discomfort. Untreated pain, constipation and not being able to empty the bladder.
• Alcohol withdrawal, sometimes in a person no one realized was drinking every day at home.

Much of it is preventable. The American Geriatrics Society says delirium can be prevented up to 40 percent of the time in older hospital patients, with steps that are anything but high-tech: walking several times a day, reminders of the date and place, unbroken sleep at night, enough fluids, good pain control, and glasses and hearing aids in use.

Slower conditions that look like dementia

Delirium is the look-alike that arrives over a weekend. A few treatable conditions mimic dementia more slowly, over months, and get filed under "getting older" because nobody went looking.

• Medications taken for years. Drugs with anticholinergic effects, prescribed for sleep, bladder control or stomach problems, can dull memory and attention over time. So can benzodiazepines and opioids.
• Depression. In later life it can look a lot like early dementia, and the two often go together. A review in Nature Reviews Neurology reported major depression in up to 20 percent of people with Alzheimer's and up to half of people with vascular dementia. Depression usually improves with treatment.
• Vitamin B12 deficiency and thyroid problems. Depending on how it's measured, the NIH Office of Dietary Supplements puts B12 deficiency at between 3 and 43 percent of older adults living at home. Both B12 and thyroid levels are routine blood tests in any memory workup.

None of this can be sorted out at the kitchen table. It's the reason to ask for a proper evaluation. If the change has been gradual, our guide to the stages of dementia explains what a first evaluation involves.

When delirium and dementia happen together

Existing dementia is one of the strongest risk factors for delirium. A parent with mild dementia who goes into the hospital with a broken hip is the textbook case. When delirium lands on top of dementia, the decline can look enormous.

The way geriatricians think about it helps: the delirium is a separate event on top of the dementia, not the dementia suddenly racing ahead. The work of the next few weeks is to clear the delirium so the person's real baseline can be seen again. Many people return to where they were, or close to it.

Not everyone does. Research has linked episodes of delirium with faster memory decline afterward, especially in people who already had dementia. That's the strongest argument for preventing it and catching it early.

How long it lasts

Delirium can last a few hours or several weeks or months. Mayo Clinic notes that recovery is usually quicker when the cause is found and treated. Recovery is often slower for people who already had dementia, were very ill, or have several health problems.

Many people go home before it has cleared. A 2022 review in the journal Delirium found that about 36 percent of older patients with delirium in the hospital still had it at discharge. At home, expect a gradual return with good days and bad days. Tell the doctor if things get worse instead of slowly better.

How families can help recovery

In the hospital

• Bring glasses, hearing aids and dentures, and make sure they're used.
• Tell the nurses what your parent was like the week before: whether she lived alone, read the paper, managed her own pills.
• Bring a few photos and familiar things from home.
• Ask whether any new medications could cause confusion, especially sleep aids, antihistamines and opioids.
• Ask whether she's being walked, and whether her sleep is protected.
• Be there as much as you can, especially in the evening.

At home

The same ideas apply. Keep days predictable: light and activity during the day, dark and quiet at night. Meals at regular times, with someone at the table. Drinks within reach. Glasses on, hearing aids in. A familiar voice in the room as evening comes. Many of the strategies in our guide to managing sundowning help with delirium recovery too.

And when something changes suddenly, treat it as urgent. A parent who was fine on Tuesday and confused on Thursday should be seen that day. Tell the doctor plainly: "This started in the last few days. She wasn't like this last week. I'd like to know why."

Steady days help the brain recover

Recovery from delirium depends a great deal on the ordinary rhythm of the weeks after discharge, and that's the part the family is left holding.

Our hospital-to-home care covers those first weeks: medication reminders, fluids, short walks, meals at regular times, and someone calm and familiar in the room. Our caregivers tell you and our office about changes the same day, so a bad afternoon gets noticed and a worsening trend reaches the doctor quickly. Personal care adds help with bathing, dressing and getting around safely. When delirium has uncovered or worsened dementia, our Alzheimer's and dementia care brings caregivers trained to reassure rather than correct.

If your parent is coming home from the hospital and you're not sure what the first few weeks should look like, talk with our care team. We can often have help in place for the day of discharge.