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March 25, 2026

Delirium vs dementia

Tobi Pomeroy, NP

Medically reviewed by:
Tobi Pomeroy, NP

Delirium vs dementia may seem similar, especially in older adults.

However, one develops suddenly and can cause serious complications if not treated right away. Knowing the difference helps you get the right care and support.1

What is dementia, and why does it happen?

Dementia is cognitive decline. It is a broad term for brain conditions that cause the gradual loss of mental functioning.

This includes2:

  • Focus
  • Memory
  • Concentration
  • Reasoning
  • Thinking
  • Language
  • Problem-solving

Alzheimer’s disease is the most common form of dementia. It accounts for between 60 to 80% of all cases.3 There are also many other types of dementia. Vascular dementia, Lewy body dementia and frontotemporal dementia are other types.

Dementia occurs when nerve cells and connections in the brain become damaged or severed. It can be caused by a wide range of risk factors. Some risk factors are depression, diabetes and heavy alcohol use.4 Some medical conditions may also increase the risk for dementia. Down syndrome and stroke are linked to this condition.

Symptoms of dementia are different for everyone. They vary based on the part of the brain affected. Common signs and symptoms include5:

  • Getting lost in familiar places
  • Forgetting the names of familiar people
  • Forgetting long-held memories
  • Using unusual or inappropriate words
  • Not knowing the season, month or year
  • Sudden changes in mood and behavior
  • Repeating questions or comments within a short period
  • Problems with performing everyday tasks

What is delirium, and why does it happen?

Delirium is a sudden, temporary state of mental confusion. There may also be disorientation and a lack of awareness.1 It comes on quickly within a few hours or days and resolves just as fast. A person with delirium may suddenly start acting out of character and unlike their usual self.

There are many possible causes of delirium. Some causes are1:

  • Brain inflammation
  • Sleep disturbances
  • Chemical imbalances
  • Infections
  • Certain medications
  • Drug and alcohol withdrawal

Many times, underlying dementia can trigger delirium.6 Dementia can make the brain more vulnerable to other conditions like delirium. This happens due to damaged neurons and connections.7

Symptoms of delirium typically come on quickly. They may include8:

  • Confusion and disorientation
  • Abrupt changes in alertness
  • Hallucinations
  • Problems with memory
  • Problems with concentration
  • Sleep disturbances
  • Changes in eating habits
  • Lethargy or drowsiness
  • Changes in moods and behaviors
  • Changes in personality

There are three types of delirium: hyperactive, hypoactive and mixed.1,8

Hyperactive delirium is marked by restlessness and aggression. There may also be hallucinations or delusions.

Hypoactive delirium is characterized by sleepiness, low activity level and social isolation.

Mixed delirium is a combination of both hyperactive and hypoactive delirium. There may be brief periods of hyperactivity followed by short periods of sluggishness.1,8

Anyone can be affected by delirium. However, this condition occurs most frequently in hospital settings. When caught early, delirium can be successfully treated. It may also be prevented in about 30% to 40% of cases.9

What is the role of muscle loss in delirium and dementia?

Delirium and dementia are also linked to problems related to muscle strength.

Muscle loss is also known as muscle atrophy. It is a severe symptom and side effect of both conditions.10 It can worsen both problems and lead to faster mental decline.

Dementia and delirium put older adults at risk for muscle loss for several reasons.

First, older adults tend to be less active. A delirium or dementia diagnosis may lead to less physical activity and more muscle loss.

Second, lack of exercise suppresses the body’s release of myokines. Myokines are proteins that offer protective benefits for brain health.11 Some symptoms of dementia and delirium may also lead to less physical activity.1,2,5 For instance, lethargy can lead to less activity. Lethargy is a feeling of extreme tiredness.

System-wide inflammation is another major factor linked to muscle loss in dementia. Inflammation can damage brain cells and neurons. For these reasons, it can promote mental decline.12

Fortunately, it is possible to prevent age-related muscle loss. Good nutrition and exercise can help with this.

Delirium vs dementia: how are they different?

Delirium is acute. It comes on suddenly and goes away quickly. Dementia is chronic. It happens slowly over time. Symptoms for each condition will be different for everyone. They vary based on the person and the region of the brain affected.

Here are some key differences between delirium and dementia.

Key differences between delirium and dementia
Delirium Dementia
Acute (short-term) Chronic (long-term)
Develops quickly over hours or days Develops slowly over months or years
Can get better with treatment Gets worse over time, but can be delayed
Symptoms can change quickly, by the hour Symptoms stay consistent
Considered an urgent medical emergency Requires long-term treatment & management

Similarities between delirium and dementia

Delirium vs dementia share many of the same symptoms. They are also more common in older adults than in any other people. An estimated 3% of youth are at risk for delirium. In comparison, 14% to 36% of older adults between the ages of 64 and 74 are at risk.13

Symptoms of both delirium and dementia are:

  • Confusion
  • Memory loss
  • Changes in mood and behavior
  • Difficulty speaking or finding the right words
  • Delusions and hallucinations
  • Confusion and agitation in the late afternoon or early evening

Having one condition increases your risk of getting the other. Some factors may lead to both conditions. These factors are brain inflammation, chronic stress and chemical imbalances.7

How to tell if it’s delirium or dementia

It can be difficult to know whether someone has delirium or dementia based on their symptoms. This is especially true if you do not know the person very well.

Here are some key points that may help:

  • Did symptoms come on quickly or slowly? Delirium develops over a few hours or days. Dementia develops slowly over months or years.
  • Do symptoms change quickly, or do they typically stay the same? Delirium symptoms can change quickly from one moment to the next. Dementia symptoms usually stay the same from day to day.
  • Was there recently an acute illness? Delirium can often be triggered by acute conditions. These include urinary tract infections (UTIs), drug misuse and dehydration. Drug and alcohol withdrawal may also cause delirium.
  • Are there any hallucinations or delusions? These symptoms occur in both dementia and delirium. But they are more common with delirium.
  • What type of mood changes have occurred? Anger, combativeness and agitation are common mood changes that occur with delirium. Depression and anxiety are common mood changes that occur with dementia.
  • Are there changes in speech and language? People with dementia often struggle to find the right words. Those with delirium may talk slowly and use inappropriate words and phrases.

When to see a doctor

Make an appointment with your doctor if you or a loved one has symptoms of dementia or delirium. Both are serious conditions that can progress and get worse without medical treatment.

Delirium is a medical emergency. It should be diagnosed as soon as possible when suspected. If not addressed right away, delirium can quickly lead to complications.

Complications of delirium include1:

  • Pneumonia
  • Malnutrition
  • Infections
  • Pressure ulcers
  • Long-term hospital stays
  • Decreased mobility
  • Increased risk of falls and injuries
  • Long-term cognitive impairment

Contact your doctor as soon as you notice your loved one is behaving oddly or strangely.

Before visiting the doctor, gather any information and documents that may help with the diagnostic process. This may include the names of medications and supplements your loved one is taking. You may also want to mention recent life or health changes that may be causing symptoms. Examples of such changes include:

  • Moving to a new home
  • The loss or death of a loved one
  • Retirement
  • Hearing loss
  • A new health diagnosis

Managing and preventing delirium

Many cases of delirium can be successfully treated. They may also be resolved within a short time. Identifying the root cause of delirium may lead to a faster recovery. Here are steps you can take when caring for someone with delirium:

  • Talk to the person in a calm manner
  • Use short sentences and simple vocabulary
  • Show them familiar objects, such as photographs
  • Encourage the person to walk around and help, if needed
  • Make sure hearing aids and eyeglasses are nearby and being used
  • Set up a regular sleep schedule
  • Display clocks and calendars prominently in the person’s home
  • Remind the person who they are, who you are and where they are
  • Provide reassurance when there are hallucinations or delusions
  • Avoid new people, environments and experiences
  • Treat the person with dignity and respect

Your healthcare provider can connect you with resources if you need a caregiver or other support when caring for someone with dementia or delirium. Medicare may also cover some services for each stage of dementia. Medicare coverage for dementia may include14:

  • Care planning
  • Cognitive assessments
  • Home safety evaluations
  • Hospital stays
  • Prescription drugs, under Medicare Part D

The Centers for Medicare & Medicaid Services is currently running a nationwide test to support people with dementia and their unpaid caregivers.15 The initiative, known as The Guiding an Improved Dementia Experience (GUIDE) Model, wants to

  • Improve the quality of life for people with dementia
  • Reduce the burden on unpaid caregivers
  • Help people with dementia remain in their homes and communities

Ask your doctor to learn more about the potential benefits of Medicare and Medicaid services for dementia.

How WellMed can help

WellMed is dedicated to providing quality health care with a strong focus on prevention. Our healthcare professionals can work with you to keep your brain healthy as you age and develop a personalized treatment plan for dementia or delirium. Contact WellMed today at (888) 781-WELL or visit our website to find a doctor near you.

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