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The Difference Between Delirium and Dementia

Dementia and delirium are 2 health problems that change a person’s mental state. They both affect the ability to think clearly. They share other similar symptoms. But they have different causes. And they have different treatment and outcomes.

Delirium is a medical emergency. It needs to be treated right away. But it can often be mistaken for dementia. In some cases, they can occur at the same time. Learn what you can do to help a person who has signs of 1 or both of these conditions.

What is delirium?

  • Delirium is a sudden change in a person’s mental state. It changes over short periods of time.

  • They will have trouble paying attention. They may have trouble following a conversation. Their thinking and speech may be confused and unclear.

  • They may vary from agitated to sleepy.

  • Delirium is a medical emergency. Usually, there is a cause.

  • Delirium is treated by finding the cause. Once the cause is treated, the delirium can go away.

What is dementia?

Dementia is a long-term disease. It has a range of symptoms that mean a person’s brain is losing function. A person’s ability to think, remember, and communicate gets worse over time. These changes are permanent. This process occurs over years. It can happen quickly or slowly. This depends on the cause.

At first, a person may sometimes be forgetful or confused. Symptoms may be mild. As the condition gets worse, the person will repeat questions. They may forget basic information. Over time, they'll have trouble following directions and doing daily tasks. They'll have trouble talking with and understanding people. They may forget who people are. They may not know where they are. They may also be moody or restless.

In some cases, dementia can occur suddenly. For example, a stroke or head injury can cause permanent trouble with thinking and communication. In these cases, dementia may not get worse with time.

People with dementia are at risk of also having delirium. This means a person with dementia may have worse symptoms due to another health problem. When the health problem is treated, the symptoms may improve. But the person will still have dementia.

Knowing the difference




Common signs

Signs include forgetfulness and confusion. The person will have trouble speaking with and understanding others. This occurs over long periods of time.

Signs include sudden changes in mental state. Changes may range from agitation to tiredness.

When signs appear

There is a slow change in mental state and behavior over months or years.

There is a sudden change in mental state and behavior over hours or days.

Thinking and attention

The person may often seem confused. Over time, their thinking won't make sense. They won't be able to focus well. They often won't be able to talk with or understand people well. In some cases, they may see or hear things that others can’t (hallucinations). They won't be able to remember events that just happened. They'll lose memories of events in the past. They may not remember who people are. They may not know where they are. They may not recognize common objects.

The person may be confused. They may have trouble focusing and talking with people. It's likely they won't be able to tell a healthcare provider about their symptoms. They may see or hear things that others can’t (hallucinations). They may not be able to remember something that just happened.

Getting a diagnosis

A person with signs of dementia or delirium will need to be diagnosed correctly. In some cases, you can help. You can tell the healthcare provider how the person's mental state is different from their normal state. This can help the provider diagnose the problem.

Healthcare providers will look at different parts of a person's health. They'll look at what medicine a person is taking. They'll see if the person has an infection. They'll find out if they have an illness that's gotten worse. They may talk with the person to learn more about their mental state. And they may do tests to see if there may be a cause for delirium.

Tests for dementia and delirium include blood and urine tests, and an MRI or CT scan of the brain. Delirium is an emergency. The person may need to be in the hospital until the cause is found.

When to get medical help

Someone with dementia may also have signs of delirium. This may mean that there is another health problem.

If someone has sudden changes in mental state, call their healthcare provider right away. Or call 911. Tell the provider about the changes in mental state that you have seen.

To learn more

Contact these groups:

© 2000-2024 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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