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Delirium vs. Dementia: What's the Difference?

By Angelike GauntSeptember 24, 2021
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Delirium and dementia are common causes of cognitive impairment in older adults. Although anyone can experience delirium symptoms, this mental disturbance is more common in seniors, affecting up to 50% of older adults at some point in life.

Dementia and delirium symptoms can be similar, so how do you know what’s causing your elderly loved one’s confusion? Read on to understand key differences between the two conditions.

What is delirium?

Delirium is a mental state that affects cognitive function. It can impair attention, thinking ability, and alertness. Delirium is not a disease — the term is often used to describe mental confusion as a result of different conditions or contributing factors, such as chronic illness, medication side effects, infections, and alcohol or drug intoxication.

What are delirium symptoms?

People with dementia and those experiencing delirium can both show signs of confusion and decreased awareness. Whether your family member has dementia or delirium, they may have difficulty following a conversation, may not understand where they are, or may not remember important facts, such as what day it is, where they live, or their loved ones’ names.

However, contrary to dementia symptoms which develop gradually over time, delirium symptoms occur suddenly, often within hours or days. Delirium symptoms usually indicate a serious, new problem that requires medical attention, especially in older adults.

If your aging loved one suddenly experiences one or more of the following symptoms, an immediate visit to the doctor or emergency room is warranted:

  • Confusion. Rambling or saying things that don’t make sense. Having trouble understanding what is being said.
  • Disorientation. Not knowing where one is or what day it is.
  • Difficulty with attention and concentration. Suddenly unable to focus. May be easily distracted by unimportant things.
  • Apathy. Acting distant and withdrawn.
  • Agitation. Restlessness, anxiousness, aggression.
  • Speech problems. E.g., slow, slurred speech.
  • Memory problems. Difficulty remembering recent events and, sometimes, events in the distant past.
  • Hallucinations. Seeing things that don’t exist.

The good news is delirium symptoms are usually temporary and reversible. Once the cause of your loved one’s delirium is treated, symptoms often go away.

Is it delirium or dementia? 

It can be difficult to distinguish between delirium and dementia. In some cases, older adults can have both. People with dementia may sometimes have delirium episodes, where they experience periods of extreme mood changes, hallucinations, and increased confusion.

However, although delirium is common in people with dementia, having delirium episodes doesn’t necessarily mean your loved one has dementia. Many things can cause delirium symptoms.

Delirium vs. dementia: How do I know what’s causing my loved one’s symptoms?

While only a doctor can tell what’s causing your loved one’s condition, there are certain key differences between delirium and dementia symptoms:

Symptoms of delirium Symptoms of dementia
Begin suddenly and develop quickly.Begin gradually and progress over time.
Have a defined starting point.Have an uncertain beginning point.
Are temporary and reversible.Are permanent and worsen as the disease progresses.
Difficulty with attention is the main early, noticeable symptom.Difficulty remembering recent events is the main early, noticeable symptom.
Slow, slurred speech is common during delirium episodes.Speech problems associated with dementia usually consist of trouble putting thoughts into words, forgetting common words, or repeating words or phrases.

What are common causes of delirium?

Anyone can experience delirium symptoms as a result of illness or intoxication. The following are common causes of delirium in older adults:

  • Medication side effects. Pain, sleep, and allergy medications, among others, can trigger delirium symptoms.
  • Dehydration. When severe, dehydration in older adults may cause mental confusion.
  • Infections, such as pneumonia or urinary tract infections.
  • Prolonged sleep deprivation, which could be a result of insomnia, changes in sleep pattern that occur with age, or other problems.
  • Severe chronic or terminal illness, such as kidney or liver failure.
  • Other medical conditions, such as stroke, Parkinson’s disease, heart attack, or chronic obstructive pulmonary disease.
  • Hospitalization and surgery. Elderly adults may become disoriented in an unfamiliar environment, such as a hospital, and may experience delirium. The stress that comes with surgery, along with anesthesia and pain medication, can also trigger delirium symptoms.

The doctor will review your family member’s list of medications and ask about their symptoms, including changes in memory, thinking, and behavior. If the doctor suspects dementia, they may use specific cognitive assessment tools, such as the Mini-Mental State Exam (MMSE) or the Montreal Cognitive Assessment (MoCA), to assess your loved one’s cognitive skills and memory.

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Confusion in elderly adults: How you can help

If your loved one seems confused, talk to their doctor. It’s important to know that delirium is usually a sign of a serious medical problem that requires immediate care.

  • Stay connected. Check in with your elderly loved one often. If you don’t live nearby, use technology to stay in touch and check on their health and well-being.
  • Pay attention to changes. No one knows your loved one better than you. Paying attention to subtle changes that may be easily missed by the doctor or hospital staff can help your loved one get the care and treatment they need as soon as possible.
  • Speak up. Does your loved one seem too quiet and distant? Do they seem confused and disoriented? If they are not acting quite like themselves, let the doctor know.
  • Seek immediate care. If you notice a sudden difference in your senior’s mental state or behavior, it’s important to seek medical care right away.
  • Discuss unusual symptoms. Talk to the doctor about any unusual symptoms or behaviors you may notice, even if you’re not sure they’re related. Always bring a list to appointments of all medications your loved one takes.
  • Lend a hand during recovery. Although delirium symptoms are usually temporary, it may take some time for elderly adults to fully recover after a delirium episode. Be prepared to help your loved one with daily activities during this time, or seek other care options, such as a short-term stay at an assisted living community, which can offer help with meals, dressing, bathing, medication management, and more.


Merck Manual. “Delirium.”

Lippman S, Perugula ML. “Delirium or dementia?”

Johns Hopkins Medicine. “Dementia and delirium.”

Angelike Gaunt

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