Changes in thinking and behavior are often associated with aging, but not all cognitive shifts originate from the same cause. Two conditions that frequently come up in discussions about brain health in later life are delirium and dementia. They share some outward signs, yet they differ sharply in how they begin, how they progress, and what they imply for long-term health.
Delirium and dementia are disorders that can be difficult to distinguish and understand. Both can lead to impaired functioning, memory loss, poor judgment, and diminished communication skills. Although it may be challenging to differentiate between delirium and dementia, there are many differences between the two.
What is Dementia?
Dementia is an umbrella term for a group of disorders that impair memory, decision-making, and other cognitive functions.
Alzheimer’s disease is the most prevalent kind, accounting for 60–80% of cases [1]. Alzheimer’s patients frequently struggle with remembering recent events, and as the disease progresses, personality changes may occur.
About 10% of dementia cases are vascular dementia, the second most common type of dementia, which is caused by strokes and problems with the blood supply to the brain [2].
Most people with dementia develop symptoms after the age of 65, although it is not a normal part of aging.
What is Delirium?
Delirium is a sudden disturbance in thinking and awareness that makes it hard to stay focused, alert, or oriented. It results in confusion, disordered thinking, inattention, and distractibility. A person may have less awareness of their surroundings and may have hallucinations or delusions.
Delirium can occur at any age, but it is more common among older adults and those in hospitals. During their hospital stay, 29–64% of older persons experience delirium [3]. Additionally, it is prevalent among patients in intensive care units, following surgery, and among residents of nursing homes.
Dementia vs Delirium: Symptoms
Several symptoms of dementia and delirium are similar, and they can have similar outcomes, such as people falling, becoming lost, or getting hurt. Delirium also increases the risk of developing dementia.
Sometimes an individual may have both. Dementia patients have an increased risk of delirium.
People with delirium experience altered awareness, which mostly impairs their focus. They may struggle to focus, maintain, and shift their attention. Meanwhile, dementia primarily impacts memory.
Dementia Symptoms
Symptoms of dementia can vary significantly from one person to another [4]. Individuals with dementia may experience issues with:
- communication
- attention
- memory
- visual perception
- judgment, reasoning, and problem-solving
Some symptoms that could signify a person has dementia are:
- forgetting the names of close family and friends
- not being able to complete tasks independently
- getting lost in the neighborhood
- forgetting memories
- forgetting the names of familiar things
Delirium Symptoms
Delirium symptoms usually appear within a few hours or days. Symptoms may fluctuate throughout the day, and individuals may experience times without any symptoms.
Additionally, they tend to decrease during the day and worsen at night or in an unfamiliar environment.
Typical symptoms and indicators include:
- Inattention, or trouble focusing, shifting, or retaining attention
- Confusion, or not knowing who they are, where they are, or the time
- Slurred, confused, or rambling speech.
- Emotional changes, such as anxiety, irritation, anger, depression, and fear
- Abrupt changes in mood
- Agitation, hostility, or restlessness
- Perceptual abnormalities like illusions or hallucinations
- Being quiet, distant, drowsy, or lethargic
- Disrupted eating and sleeping habits
- Changes in personality
Dementia vs Delirium: Causes
According to experts, degeneration of particular brain cells causes dementia. This is a delirium risk factor. When people with dementia have an illness like an infection, they are particularly vulnerable to abrupt and severe cognitive and behavioral issues.
Delirium is also a risk factor for dementia because brain cells are prone to long-term damage due to recurring episodes of temporary impairment of brain function [4].
More specific causes of dementia and delirium are as follows.
Dementia Causes
Dementia is a neurodegenerative disorder characterized by the progressive loss or damage of neurons (nerve cells) in the brain. This inhibits communication between different parts of the brain. Specific brain alterations are also responsible for dementia [5].
Dementia may result from the following conditions:
- Huntington’s disease
- Parkinson’s dementia
- Pick’s disease
- Alzheimer’s disease
- Vascular dementia
- Lewy body dementia
- Frontotemporal dementia
- Down syndrome
- Creutzfeldt-Jakob disease
- Stroke
- Brain tumors
- Traumatic brain injuries
Delirium Causes
Several factors that cause delirium include:
- dementia
- electrolyte imbalances due to dehydration and thyroid dysfunction
- sensory or sleep deprivation
- hospitalization or surgery
- metabolic disorders
- organ failure, including kidney or liver failure
- brain, heart, lung, and liver conditions
- infections, such as untreated urinary tract infections (UTIs), pneumonia, and the flu
- unfamiliar environment
- intoxication or withdrawal from drugs or alcohol
- certain medications, such as opioids, psychoactive drugs, and anticholinergics
- abruptly stopping medication or taking insufficient medication
Dementia vs Delirium: Risk Factors
The following are the risk factors of dementia and delirium.
Dementia Risk Factors
The risk factors of dementia include
- 65 years of age and older
- Family history of dementia (having siblings or parents with dementia)
- Genetics (certain genes are linked to a higher risk)
- Sex (more women than men live with dementia due to longer life span than men)
- Down syndrome
- High cholesterol
- High blood pressure
- A history of stroke, heart disease, or vascular disease
- Smoking
- Diabetes
- Poor diet
- Depression
- Lower levels of education
- Physical inactivity
- Air pollution
- Head injuries (such as traumatic brain injuries)
- Poor sleep
- Hearing loss
- Social isolation
Delirium Risk Factors
A person is more likely to have delirium if they have the following risk factors [6]:
- Male
- Over 70 years of age
- Brain conditions such as dementia
- Alcohol intoxication
- Multiple coexisting disorders
- Taking multiple medications
Dementia vs Delirium: Diagnosis
Doctors diagnose dementia and delirium using different procedures.
Dementia Diagnosis
A doctor will perform tests to rule out other potential causes of the symptoms. A neurologist will do extensive cognitive and neurological tests to assess the individual’s mental ability.
Additionally, they could order brain scans, such as PET, MRI, and CT scans, for potential disorders that could be causing dementia-like symptoms. These scans may also reveal structural and functional alterations in the brain.
A doctor may request genetic testing in certain circumstances, such as Huntington’s disease and early and late-stage Alzheimer’s disease.
Delirium Diagnosis
An immediate assessment is necessary for delirium. A doctor examines the patient’s medical history, performs a physical examination, and reviews test results to diagnose delirium. These will assist the physician in determining if the person’s altered mental state is directly related to an underlying medical issue or other factors like exposure to toxins.
The Confusion Assessment Method (CAM) is a standard tool doctors employ to identify delirium [7]. CAM has four key components:
- Acute onset and fluctuating course
- Inattention
- Disorganized thinking
- Altered level of consciousness
Dementia vs Delirium: Treatment
Dementia and delirium have distinct therapeutic approaches.
Dementia Treatment
Although there is no cure for dementia, certain medications can help manage symptoms or slow cognitive decline. Historically, treatments such as cholinesterase inhibitors and memantine have been used to ease memory and thinking issues.
More recently, the U.S. Food and Drug Administration (FDA) has approved Lecanemab (Leqembi) and Donanemab (Kisunla). These newer drugs target underlying disease changes (amyloid buildup in the brain) and can slow progression in early Alzheimer’s.
Non-drug therapies may also be effective in improving or maintaining cognitive function. These include:
- physical activity
- cognitive exercises
- memory training
- social stimulation
Delirium Treatment
To effectively treat delirium, it is essential to identify and address the underlying cause. It could involve stopping medicine or treating an infection.
All delirium reasons require the creation of a tranquil environment. While the patient is receiving treatment, a calm environment may help keep the disease from worsening.
Healthcare providers may also concentrate on treating delirium-related complications, such as enhancing pain management, sleep, and nutrition.
If a physician believes that a patient or others are in danger, they may also prescribe medicine.
Dementia vs Delirium: A Summarized Comparison
| Feature | Delirium | Dementia |
| Onset | Sudden (hours to days) | Gradual (months to years) |
| Course | Fluctuating; may improve with treatment | Slowly progressive; usually irreversible |
| Attention | Impaired; hard to focus | Usually normal early; declines gradually |
| Awareness | Reduced; confusion about surroundings | Generally alert until later stages |
| Memory | Short-term memory affected suddenly | Memory loss develops slowly over time |
| Thinking | Disorganized, confused, sometimes hallucinations | Impaired reasoning and judgment over time |
| Mood & Behavior | Rapid mood swings, agitation, anxiety, or lethargy | Personality changes over time; apathy, depression, or irritability may develop |
| Duration | Days to weeks; reversible if cause treated | Long-term, chronic |
| Reversibility | Often reversible if underlying cause is treated | Usually irreversible; treatments manage symptoms and slow progression |
| Causes | Infection, medications, metabolic disturbances, dehydration, surgery, hospitalization | Alzheimer’s disease, vascular dementia, Lewy body dementia, frontotemporal dementia |
| Risk Factors | Older age, male, existing cognitive impairment, serious illness, alcohol intoxication, polypharmacy | Older age, genetics, cardiovascular risk factors, head trauma, lifestyle factors |
| Diagnostic Tools | Confusion Assessment Method (CAM), clinical evaluation | Cognitive testing, neuroimaging, lab tests, clinical assessment |
| Treatment | Identify and treat underlying cause | Symptom management, supportive care, medications for Alzheimer’s |
Alzheimer’s Research Association is a non-profit organization dedicated to helping caregivers of Alzheimer’s disease and dementia. We provide the latest information and news about the illness and helpful tips to help caregivers cope with their daily caregiving challenges. We realize the most important thing that a caregiver needs is financial assistance. Therefore, we provide grants to caregivers to ease their financial burden. Caregivers can apply for grants here: Alzheimer’s Grant Application.
You can also help caregivers in their endeavor by donating as much as possible: Donation To Alzheimer’s Research Associations.
References
- What is Alzheimer’s Disease? Alzheimer’s Association. https://www.alz.org/alzheimers-dementia/what-is-alzheimers. Accessed: 9th December, 2025.
- Vascular Dementia. National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health/vascular-dementia. Last Updated: 28th September, 2022. Accessed: 9th December, 2025.
- Van Velthuijsen, E.L., Zwakhalen, S.M., Mulder, W.J., Verhey, F.R. and Kempen, G.I., 2018. Detection and management of hyperactive and hypoactive delirium in older patients during hospitalization: a retrospective cohort study evaluating daily practice. International journal of geriatric psychiatry, 33(11), pp.1521-1529.
- Fong, T.G., Davis, D., Growdon, M.E., Albuquerque, A. and Inouye, S.K., 2015. The interface of delirium and dementia in older persons. The Lancet. Neurology, 14(8), p.823.
- Emmady, P.D., Schoo, C. and Tadi, P., 2020. Major neurocognitive disorder (dementia).
- Jandu, J.S., Mohanaselvan, A. and Fang, X., 2025. Differentiating Delirium Versus Dementia in Older Adults. In StatPearls [Internet]. StatPearls Publishing.
- Grover, S. and Kate, N., 2012. Assessment scales for delirium: A review. World journal of psychiatry, 2(4), p.58.
- Tee-Melegrito, R. Delirium vs. dementia: What to know. Medical News Today. https://www.medicalnewstoday.com/articles/delirium-vs-dementia. Published Online: 3rd March, 2023. Accessed: 10th December, 2025.
- Heerema, E. Differences Between Delirium and Dementia. Very Well Health. https://www.verywellhealth.com/whats-the-difference-between-delirium-and-dementia-98838. Updated on: 10th November, 2025. Accessed: 10th December, 2025.
