What Is Dementia? Symptoms, Types, and Diagnosis

Dementia is the loss of cognitive functioning — thinking, remembering, and reasoning — to such an extent that it interferes with a person’s daily life and activities. Some people with dementia cannot control their emotions, and their personalities may change. Dementia ranges in severity from the mildest stage, when it is just beginning to affect a person’s functioning, to the most severe stage, when the person must depend completely on others for basic activities of living.

Dementia is more common as people grow older (about one-third of all people age 85 or older may have some form of dementia) but it is not a normal part of aging. Many people live into their 90s and beyond without any signs of dementia.

There are several different forms of dementia, including Alzheimer’s disease. A person’s symptoms can vary depending on the type.

What are the signs and symptoms of dementia?

Signs and symptoms of dementia result when once-healthy neurons, or nerve cells, in the brain stop working, lose connections with other brain cells, and die. While everyone loses some neurons as they age, people with dementia experience far greater loss.

The symptoms of dementia can vary and may include:

• Experiencing memory loss, poor judgment, and confusion
• Difficulty speaking, understanding and expressing thoughts, or reading and writing
• Wandering and getting lost in a familiar neighborhood
• Trouble handling money responsibly and paying bills
• Repeating questions
• Using unusual words to refer to familiar objects
• Taking longer to complete normal daily tasks
• Losing interest in normal daily activities or events
• Hallucinating or experiencing delusions or paranoia
• Acting impulsively
• Not caring about other people’s feelings
• Losing balance and problems with movement

People with intellectual and developmental disabilities can also develop dementia as they age, and recognizing their symptoms can be particularly difficult. It’s important to consider a person’s current abilities and to monitor for changes over time that could signal dementia.

What causes dementia?

The causes of Alzheimer’s and related dementias can vary, depending on the types of brain changes that may be taking place. While research has found that some changes in the brain are linked to certain forms of dementia, in most cases, the underlying causes are unknown. Rare genetic mutations may cause dementia in a relatively small number of people.

Although there is no proven prevention, in general, leading a healthy lifestyle may help reduce risk factors that have been associated with these diseases.

What are the different types of dementia?

Various disorders and factors contribute to the development of dementia. Neurodegenerative disorders result in a progressive and irreversible loss of neurons and brain functioning. Currently, there are no cures for these diseases.

The five most common forms of dementia are:

• Alzheimer’s disease, the most common dementia diagnosis among older adults. It is caused by changes in the brain, including abnormal buildups of proteins, known as amyloid plaques and tau tangles.
• Frontotemporal dementia, a rare form of dementia that tends to occur in people younger than 60. It is associated with abnormal amounts or forms of the proteins tau and TDP-43.
• Lewy body dementia, a form of dementia caused by abnormal deposits of the protein alpha-synuclein, called Lewy bodies.
• Vascular dementia, a form of dementia caused by conditions that damage blood vessels in the brain or interrupt the flow of blood and oxygen to the brain.
• Mixed dementia, a combination of two or more types of dementia.

Other conditions that cause dementia-like symptoms can be halted or even reversed with treatment. For example, normal pressure hydrocephalus, an abnormal buildup of cerebrospinal fluid in the brain, often resolves with treatment.

In addition, medical conditions such as stress, anxiety, depression, and delirium can cause serious memory problems that resemble dementia, as can side effects of certain medicines.

Researchers have also identified many other conditions that can cause dementia or dementia-like symptoms. These conditions include:

• Argyrophilic grain disease, a common, late-onset degenerative disease
• Creutzfeldt-Jakob disease, a rare brain disorder
• Huntington’s disease, an inherited, progressive brain disease
• Chronic traumatic encephalopathy, caused by repeated traumatic brain injury
• HIV-associated dementia, a rare disease that occurs when the HIV virus spreads to the brain

The overlap in symptoms of various dementias can make it difficult to get an accurate diagnosis. But a proper diagnosis is important to get the best treatment.

How is dementia diagnosed?

To diagnose dementia, doctors first assess whether a person has an underlying, potentially treatable, condition that may relate to cognitive difficulties. A physical exam to measure blood pressure and other vital signs, as well as laboratory tests of blood and other fluids to check levels of various chemicals, hormones, and vitamins, can help uncover or rule out possible causes of symptoms.

A review of a person’s medical and family history can provide important clues about risk for dementia. Typical questions might include asking about whether dementia runs in the family, how and when symptoms began, changes in behavior and personality, and if the person is taking certain medications that might cause or worsen symptoms.

The following procedures also may be used to diagnose dementia:

• Cognitive and neurological tests. These tests are used to assess thinking and physical functioning. These include assessments of memory, problem solving, language skills, and math skills, as well as balance, sensory response, and reflexes.
• Brain scans. These tests can identify strokes, tumors, and other problems that can cause dementia. Scans also identify changes in the brain’s structure and function. The most common scans are:
  • Computed tomography (CT), which uses X-rays to produce images of the brain and other organs
  • Magnetic resonance imaging (MRI), which uses magnetic fields and radio waves to produce detailed images of body structures, including tissues, organs, bones, and nerves
  • Positron emission tomography (PET), which uses radiation to provide pictures of brain activity
• Psychiatric evaluation. This evaluation will help determine if depression or another mental health condition is causing or contributing to a person’s symptoms.
• Genetic tests. Some dementias are caused by a person’s genes. In these cases, a genetic test can help people know if they are at risk for dementia. It is important to talk with a genetic counselor before and after getting tested, along with family members and the doctor.
• Blood tests. It is now possible for doctors to order a blood test to measure levels of beta-amyloid, a protein that accumulates abnormally in people with Alzheimer’s. Several other blood tests are in development. However, the availability of these diagnostic tests for Alzheimer’s and related dementias is still limited.

Early detection of symptoms is important, as some causes can be treated. However, in many cases, the cause of dementia is unknown and cannot be treated. Still, obtaining an early diagnosis can help with managing the condition and planning ahead.

Sometimes, a person with dementia will agree to donate their brain. Brain donation helps researchers study brain disorders, such as Alzheimer’s disease and related dementias, which affect millions of people. By studying the brains of people who have died, researchers learn more about how types of dementia affect the brain and how we might better treat and prevent them. When donating as part of a research study or to the NIH NeuroBioBank, there is no cost to the family for the donation and an autopsy report.

Who can diagnose dementia?

Visiting a primary care doctor is often the first step for people who are experiencing changes in thinking, movement, or behavior. However, neurologists — doctors who specialize in disorders of the brain and nervous system — are often consulted to diagnose dementia. Geriatric psychiatrists, neuropsychologists, and geriatricians may also be able to diagnose dementia. Your doctor can help you find a specialist.

If a specialist cannot be found in your community, contact the nearest medical school neurology department for a referral. A medical school hospital also may have a dementia clinic that provides expert evaluation. You can also visit the Alzheimer’s Disease Research Centers directory to see if there is an NIA-funded center near you. These centers can help with obtaining a diagnosis and medical management of conditions.

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

Content reviewed: July 02, 2021