What Is Dementia?

Man talking to a health care provider about dementia

Dementia is an umbrella term used to describe a range of neurological conditions affecting the brain that get worse over time. It is the loss of the ability to think, remember, and reason to levels that affect daily life and activities. Some people with dementia cannot control their emotions and other behaviors, and their personality may change.

In the past, dementia was sometimes referred to as “senility” and was thought to be a normal part of aging, likely because it is more common as people age. As many as half of all people age 85 or older may have dementia. But dementia is not a normal part of aging. Not everyone develops dementia as they get older, and, in rare cases, some people develop dementia in midlife.

What Causes Dementia?

Dementia is the result of changes in the brain that cause nerve cells, or neurons, to stop working properly and eventually die. Researchers have connected changes in the brain to certain forms of dementia, but in most cases the specific brain changes that cause dementia are unknown. For a small number of people, rare genetic mutations that cause dementia have been identified.

Although some people may be diagnosed with general dementia, to best tailor treatment and prepare for the future, it is ideal to know the specific type. The five most common forms of dementia are:

  • Alzheimer’s disease is the most common dementia diagnosis among older adults. Alzheimer’s dementia is typically associated with abnormal buildups of proteins in the brain — these are known as beta-amyloid plaques and tau tangles — along with a loss of connection among nerve cells.
  • Frontotemporal dementia (FTD) is rare and tends to occur in people younger than 60. FTD is named for the areas of the brain affected. Changes in the frontal lobe lead to behavioral symptoms, whereas changes in the temporal lobe lead to problems with language and emotions. These changes include abnormal amounts or forms of the proteins tau and TDP-43, and the loss of nerve cells.
  • Lewy body dementia (LBD) symptoms include problems with thinking, movement, behavior, and mood. LBD diagnoses are typically associated with abnormal deposits of a protein called alpha-synuclein in the brain, also called Lewy bodies.
  • Vascular dementia is a diagnosis of dementia in people who have vascular changes in the brain, such as a stroke or injury to small vessels carrying blood to the brain. People diagnosed with a vascular dementia may also show changes in the brain’s white matter, i.e., the connecting "wires" of the brain that relay messages between regions.
  • Mixed dementia refers to a diagnosis of dementia that is thought to be connected to a mixture of changes in the brain. For example, a person might have evidence of changes traditionally associated with both Alzheimer’s and vascular dementias. Researchers are continuing to explore how and why multiple distinct dementia-related brain changes can develop at the same time. This will help them better understand these various disorders and develop personalized prevention and treatment strategies.

Together, the conditions are often referred to as Alzheimer’s disease and Alzheimer’s disease-related dementias because they share many features and may commonly occur together.

Many other conditions can cause dementia or dementia-like symptoms, including argyrophilic grain disease, Creutzfeldt-Jakob disease, Huntington's disease, chronic traumatic encephalopathy, and HIV-associated dementia. In addition, certain medical conditions — and even some medications — can cause serious memory problems like those seen in dementia.

Treatable Causes of Dementia-Like Symptoms

There are many conditions that can cause dementia-like symptoms that can sometimes be stopped or even reversed with treatment. These conditions include:

  • Side effects of certain medicines
  • Emotional problems, such as stress, anxiety, or depression
  • Certain vitamin deficiencies
  • Drinking too much alcohol
  • Blood clots, tumors, or infections in the brain
  • Delirium, a sudden state of confusion and disorientation
  • Head injury, such as a concussion from a fall or accident
  • Thyroid, kidney, or liver problems
  • Normal pressure hydrocephalus, an abnormal buildup of cerebrospinal fluid in the brain

Talk with your doctor if you experience serious memory problems or other symptoms of dementia. A proper diagnosis is important to getting the right treatment.

What Are the Signs and Symptoms of Dementia?

Many people associate dementia with memory loss. This is because memory problems are often one of the early symptoms of a dementia disorder, but they are not the only one. The symptoms of dementia can vary, depending on the type of dementia and what areas of the brain are affected. Symptoms may include:

  • Memory loss, poor judgment, and confusion
  • Changes in the ability to speak, understand, and express thoughts and/or words and to write and read
  • Wandering and getting lost in a familiar neighborhood
  • Trouble handling money and paying bills
  • Repeating questions
  • Using unusual words to refer to familiar objects
  • Taking longer to complete normal daily tasks
  • Loss of interest in normal daily activities or events
  • Hallucinations, delusions, and paranoia
  • Acting impulsively
  • Not caring about other people’s feelings
  • Problems with balance and movement

People with dementia and those caring for them can face great challenges, including the person’s ability to handle tasks, changes in family relationships, loss of work, and the need for more care as the underlying disease progresses. People in the earlier stages of dementia may need help with daily activities, while people with advanced dementia may need constant care and supervision.

How Is Dementia Diagnosed and Treated?

To diagnose dementia, a doctor will complete a medical history, physical exam, and neurological tests that assess balance, sensory response, reflexes, and memory and thinking skills. In addition, a doctor may order brain scans, blood tests, genetic tests, and a mental health evaluation to help determine a diagnosis.

Because different types of dementia can share similar symptoms, making an accurate diagnosis can be difficult. In addition, dementia may be difficult to diagnose as a single disease given that a person could have more than one type.

Visiting a doctor is often the first step for people who are experiencing symptoms of dementia. Your doctor may refer you to a neurologist, which is a specialist in disorders of the brain and nervous system. Neurologists generally have the expertise needed to diagnose dementia.

No treatments currently exist to stop or slow dementia caused by Alzheimer’s or related dementias. Medication may temporarily improve or stabilize memory and thinking skills in some people and may help manage certain symptoms and behavioral problems. A team of specialists — doctors, nurses, and therapists — can help with maintaining mobility; addressing speech and swallowing problems; and learning new ways to handle loss of skills with everyday tasks, such as feeding oneself.

Through substantial investments from the federal government and others, researchers continue to advance scientific growth and discovery to improve the diagnosis, treatment, and care of those living with dementia.

The Dementias: Hope Through Research

The Dementias: Hope Through Research publication

This booklet provides an overview of research on Alzheimer’s disease, frontotemporal dementia, Lewy body dementia, vascular dementia, and more. Also available in Spanish. 

What Can You Do?

If you are concerned about memory problems or other symptoms of dementia, call your doctor. If you or someone you know has recently been diagnosed, explore the resources on this website and referenced below to find out more about dementia care, support, and research. It is important to educate family, friends, and caregivers about a loved one’s diagnosis. In-person and online support groups offered by nonprofit organizations can give families and caregivers additional resources and opportunities to share experiences and express concerns. You may also consider participating in a clinical trial or study.

Older adults wearing masks volunteering for Alzheimer's research

Volunteer for Research

You could help discover new ways to treat and prevent Alzheimer’s and related dementias.

Find More Resources on Dementia

Explore the resources on this website and linked below to find more information from federal government agencies.

What Is Dementia? Symptoms, Types, and Diagnosis

Learn more about the different types of dementia and how they are diagnosed.

NINDS Dementia Information Page

Find information on dementia diagnosis and treatment, as well as clinical trials, patient organizations, and free publications.

NINDS Dementia Publications

Get free publications from NINDS on dementia. Also available in Spanish.

Dementia Health Topic on MedlinePlus

Find information on the basics of dementia and links to more resources. Also available in Spanish.

Dementia Health Topic in Multiple Languages

Access a downloadable PDF available in nine languages, including Spanish.

Myths and Facts About Dementia

Test your knowledge of dementia in this myth vs. fact article. Also available in Spanish.

Understanding Dementia

Read about dementia symptoms, stages, and care considerations. Also available in Spanish.

Understanding Reversible Dementias

Learn about the causes of symptoms that can mimic Alzheimer’s and related dementias. Also available in Spanish.

Questions? Contact the ADEAR Center

The Alzheimer’s & related Dementias Education & Referral (ADEAR) Center is a service of the National Institute on Aging at the National Institutes of Health. Call 800-438-4380 or email adear@nia.nih.gov to talk with an information specialist.


This content is provided by the National Institute on Aging (NIA), part of the National Institutes of Health. NIA scientists and other experts review this content to ensure it is accurate and up to date.