Delirium and dementia both affect a person’s thinking and lead to confusion. However, delirium starts suddenly and can be short term, while dementia develops gradually over several years and is not reversible.

Altered mental status is a general term that refers to behavior changes caused by a disruption in how the brain works. It is common in older adults.

It encompasses various presentations, including inattention, confusion, disorientation, poor memory, incoherent speech, agitation, and psychosis.

Altered mental status is common in individuals with delirium and dementia. The two conditions may also coexist.

This article explores delirium and dementia, their similarities and differences, causes, diagnosis, and treatment.

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Delirium is a disturbance in a person’s thoughts, mood, and behavior. It causes inattention, distractibility, disorganized thinking, and confusion. A person may have reduced awareness of their environment and may experience hallucinations or delusions.

Delirium may occur at any age but is more common in older adults and hospitalized individuals. Between 29–64% of older adults have delirium during their hospitalization. It is also common after surgery, in people in ICUs, and among nursing home residents.

The Centers for Disease Control and Prevention (CDC) state that dementia is a general term used to describe a group of conditions that impair memory and decision making.

The most common type is Alzheimer’s disease, which occurs in 60–80% of cases. People with Alzheimer’s often have trouble remembering recent events and may experience personality changes in later stages of the disease.

Strokes and blood-flow issues to the brain cause about 10% of dementia cases, known as vascular dementia.

Most people with dementia begin to show symptoms after 65 years of age, but the condition is not an expected part of aging.

Many of the symptoms of delirium and dementia are similar and can cause similar consequences, such as people falling, getting lost, or becoming injured. At the same time, delirium is a risk factor for subsequent dementia.

In some cases, a person may have both. People with dementia are at a higher risk of having delirium.

People with delirium have an altered awareness that mainly affects their attention. They may have problems focusing, holding, and shifting attention. Meanwhile, dementia mainly affects memory.

Delirium symptoms

Symptoms of delirium often develop within hours or days. They tend to fluctuate throughout the day, and a person may have periods without symptoms.

They also tend to lessen during the day and worsen when it is dark or when the environment is unfamiliar.

Common signs and symptoms include:

  • inattention, or difficulty focusing, shifting, or maintaining attention
  • disorientation, or not knowing who and where they are, or what time it is
  • slurred, incoherent, or rambling speech
  • emotional changes, including anxiety, irritability, anger, depression, and fear
  • sudden mood shifts
  • restlessness, agitation, or aggression
  • perceptual distortions, such as hallucinations or delusions
  • being quiet, withdrawn, drowsy, or lethargic
  • disturbed sleeping and eating habits
  • personality changes

Symptoms may vary depending on the type of delirium a person has. Experts have identified three types:

  • Hyperactive delirium: This type is the most easily recognizable for its motor symptoms, including agitation, restlessness, and sometimes aggressiveness. A person with this type may have rapid mood shifts, hallucinations, and refuse to cooperate with their care.
  • Hypoactive delirium: This type is known for reduced motor activity or inactivity. Common symptoms include sluggishness, slow speech, and apathy. A person with this type may also appear sedated.
  • Mixed delirium: This type presents with symptoms of both hypoactive and hyperactive delirium. They may switch from one state to the other.

Dementia symptoms

According to the CDC, the symptoms of dementia can vary widely from person to person. People with dementia may have problems with:

  • communication
  • attention
  • memory
  • visual perception
  • judgment, reasoning, and problem-solving
  • depression

Some signs that may indicate a person has dementia include:

  • forgetting the names of close family and friends
  • being unable to complete tasks independently
  • getting lost in their neighborhood
  • forgetting older memories
  • forgetting the names of familiar objects

Learn more about the symptoms of dementia here.

Side-by-side comparison of symptoms

See the table below for a side-by-side comparison of delirium versus dementia symptoms:

Onsetabrupt onset with a definite beginning pointslow and gradually progressive, with an unclear starting point
Durationdays to weeks, but may be longermonths to years, usually permanent except for reversible causes of dementia, such as thyroid dysfunction, vitamin B12 deficiency, and normal pressure hydrocephalus
Courseoften temporary and reversible when doctors identify and treat the cause slow, persistent, and progressive course; incurable
Symptom fluctuationfluctuates frequently and significantly throughout the dayattention and thinking skills are relatively constant throughout the day
Causespecific illnesses such as urinary tract infection (UTI), dehydration, drug use, or drug and alcohol withdrawaltypically, conditions such as Alzheimer’s disease, frontotemporal dementia, vascular dementia, or other related disorders
Perceptual disturbancesvery commonoccasionally occur
Behavior/moodusually causes combativeness and anger usually causes depression, often with anxiety
Effect on attentionsignificantly impaired; abrupt reduction in awareness of environment and orientationgenerally alert in the early stages; affected much later when dementia is already severe
Effect at nightnighttime almost always worsens symptomsoften worsens symptoms
Consciousnessvariesnot affected until dementia has become severe
Languageslow, inappropriate, and incoherentword-finding difficulty
Memorytypically less affectedsignificantly affected throughout the course of the disease, especially recent memory
Activity leveleither overly active or underactive not affected until later stages
Need for medical attentionrequires immediate treatmentnecessary but not urgent
Effect of treatmentoften resolves with treatmenthelps slow the progression of the disease but does not cure it

Scientists believe the deterioration of specific brain cells causes dementia. This is a risk factor for delirium. People with dementia are especially at risk of experiencing sudden and severe cognitive and behavioral problems when they have an illness such as an infection. Delirium is one of the most common early symptoms of COVID-19 infection in people with dementia.

Delirium is also a risk factor for dementia because repeated episodes of temporary impairment of brain function make the brain cells susceptible to permanent damage.

The following are more specific causes of delirium and dementia.

Delirium causes

Various factors cause delirium. These include:

Certain medications can also trigger delirium, including opioids, psychoactive drugs, and anticholinergics. Suddenly going off medication or having inadequate medications can also cause delirium.

Dementia causes

Dementia is a neurodegenerative process with a progressive loss or damage of nerve cells in the brain. This prevents various areas of the brain from communicating with each other.

Specific changes in the brain also cause dementia.

Conditions that may cause dementia include:

There are various risk factors for both delirium and dementia.

Who gets delirium?

Having the following predisposing factors makes it more likely for a person to have delirium:

  • male
  • over 70 years of age
  • brain disorders such as dementia
  • alcohol intoxication
  • multiple coexisting disorders
  • taking multiple medications

Who gets dementia?

Medical professionals consider dementia a late-life condition because it tends to occur in older people. It often affects people aged 65 years and older.

Two-thirds of those diagnosed with dementia in the United States are women. The reason behind this is that women tend to live longer than men.

Genetics may also play a role. About 50% or more people with Down syndrome will develop Alzheimer’s disease as they age.

People with siblings or parents with dementia are more likely to have dementia.

The following risk factors also increase a person’s risk of dementia:

Learn more about the risk factors of dementia here.

Healthcare professionals follow different procedures when diagnosing delirium and dementia. These are listed below.

Delirium diagnosis

Delirium requires an urgent evaluation.

To diagnose it, a doctor looks at a person’s history, physical exam, and medical and lab test results. These will help the doctor determine whether the change in the person’s mental status is a direct consequence of an underlying medical condition or certain factors such as toxin exposure.

Doctors use the Confusion Assessment Method (CAM) to identify the presence of delirium. CAM includes four main features:

  1. acute onset and fluctuating course of symptoms
  2. inattention
  3. disorganized thinking
  4. altered level of consciousness

Dementia diagnosis

A doctor will run tests to rule out other possible conditions causing the symptoms. A neurologist will conduct thorough cognitive and neurological testing to evaluate the person’s mental abilities.

They may also request brain scans to identify conditions that may cause symptoms like those of dementia. These scans may also see changes in the brain’s structure and function. These include:

A doctor may sometimes ask for genetic testing, such as in Huntington’s disease and early and late cases of Alzheimer’s disease.

There are different treatment pathways for delirium and dementia. Read on to find out more.

Delirium treatment

Treatment of delirium involves identifying and addressing its underlying cause. This could include discontinuing medication or treating an infection.

Creating a calming environment is necessary for all causes of delirium. Calm surroundings may help prevent the condition from worsening while the person receives treatment.

Healthcare professionals may also focus on addressing complications caused by delirium, including improving nutrition, sleep, and pain management.

Doctors may also give medications to people with hyperactive delirium if the doctor feels the person or others are at risk.

Dementia treatment

Dementia has no cure, but treatment may help manage symptoms. Two drugs approved by the Food and Drug Administration (FDA) can help treat dementia:

  • cholinesterase inhibitors (galantamine, rivastigmine, donepezil)
  • memantine

Learn more about the best medications for memory loss.

There are also non-drug treatments that may help improve or maintain cognitive function. These include:

  • physical activity
  • cognitive exercises
  • memory training
  • social stimulation

Occupational and physical therapists may evaluate a person’s home for safety. Speech therapy may help individuals who develop dysphagia.

Besides dementia and delirium, several other brain conditions may lead to difficulties in thinking, behavior, and memory. These include:

Families and caregivers should immediately inform their doctors if a person they care for is displaying symptoms of delirium or is acting differently from their usual behavior.

It is also important to report anything that can help a healthcare professional identify the condition’s underlying cause. These include:

  • all medications the person is taking, including those they recently started or stopped
  • any environmental changes
  • any health changes, including removal of hearing aids, and changes in sleep, bowel, or bladder habits

It is also essential to ensure a person experiencing delirium is comfortable. They should have a calming environment and get enough nutrition, rest, and sleep.

Delirium is preventable in 30–40% of cases.

Delirium due to certain conditions such as drug or alcohol misuse and electrolyte imbalance typically resolves with treatment.

However, delirium may cause more extended hospital stays, increase the risk of complications, increase healthcare costs, and speed up cognitive and functional decline and death. This is especially true in people with pre-existing dementia.

Delirium and dementia are two conditions often used interchangeably or mistaken for each other. While they have several similarities, they have many characteristics that distinguish them.

Recognizing the difference between the two can help doctors provide adequate care. It can also inform family members and caregivers about their loved ones and how to best care for them.