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 daily living, such as feeding oneself.

Dementia affects millions of people and 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, which is the most common.

What are the signs and symptoms of dementia?

Signs and symptoms of dementia result when once-healthy neurons (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 signs and symptoms can vary depending on the type 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 in these cases, 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?

Dementia is the result of changes in certain brain regions that cause neurons (nerve cells) and their connections to stop working properly. Researchers have connected changes in the brain to certain forms of dementia and are investigating why these changes happen in some people but not others. For a small number of people, rare genetic variants that cause dementia have been identified.

Although we don’t yet know for certain what, if anything, can prevent dementia, in general, leading a healthy lifestyle may help reduce risk factors.

What are the different types of dementia?

Various neurodegenerative disorders and factors contribute to the development of dementia through a progressive and irreversible loss of neurons and brain functioning. Currently, there is no cure for any type of dementia.

Types of dementia include:

• 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. For example, through autopsy studies involving older adults who had dementia, researchers have identified that many people had a combination of brain changes associated with different forms of dementia.

Scientists are investigating how the underlying disease processes in different forms of dementia start and influence each other. They also continue to explore the variety of disorders and disease processes that contribute to dementia. For example, based on autopsy studies, researchers recently characterized another form of dementia known as LATE. Further knowledge gains in the underlying causes of dementia will help researchers better understand these conditions and develop more personalized prevention, treatment, and care strategies.

What is LATE?

Researchers who investigate what’s happening inside the brain after death recently helped characterize a new form of dementia: limbic-predominant age-related TDP-43 encephalopathy (LATE). LATE causes symptoms similar to Alzheimer’s, including problems with thinking, remembering, and reasoning, but has different underlying causes involving abnormal clusters of a protein called TDP-43. This protein is also involved in frontotemporal dementia, but LATE exhibits a different pattern of brain changes and tends to affect people over the age of 80. For example, a team of researchers analyzed the brains of 6,196 people with an average age at death of 88 years and found that almost 40% of them may have had LATE.

Currently, there is no way to diagnose LATE in living people. Researchers are working to further explore the causes of and risk factors for LATE and to identify pathways that could help develop methods for doctors to diagnose LATE.

Other conditions that cause dementia or dementia-like symptoms include:

• Normal pressure hydrocephalus, an abnormal buildup of cerebrospinal fluid in the brain
• 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
• Heavy alcohol use over a long period of time
• Head injury, such as a concussion from a fall or accident
• Emotional problems, such as stress, anxiety, and depression
• Delirium, a sudden state of confusion and disorientation

In addition, medical conditions such as tumors, vitamin deficiencies, medication side effects, or problems with the thyroid, kidney, or liver can also cause serious memory problems that resemble dementia. Some causes of dementia symptoms can be halted or even reversed with treatment. For example, normal pressure hydrocephalus often resolves with treatment.

The similarity in symptoms of various dementias can make it difficult to get an accurate diagnosis. But a proper diagnosis is important to get appropriate 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. Used to evaluate thinking and physical functioning, these tests 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 — such as energy use — or specific molecules in different brain regions.
• Psychiatric evaluation. If someone is experiencing behavioral or mood changes, a psychiatric evaluation may be recommended to help determine if depression or another mental health condition is causing or contributing to a person's symptoms.
• Genetic tests. Some forms of dementia are caused by a person’s genes. In these rare cases, a genetic test ordered by a doctor can help people know if they have the altered genes. It is important to talk with a genetic counselor before and after getting tested, along with family members and the doctor. There are also genetic tests that look for genetic variations that affect someone’s risk of developing dementia, but these tests cannot be used to diagnose dementia.
• Cerebrospinal fluid (CSF) tests. CSF is a clear fluid that surrounds the brain and the spinal cord, providing protection, insulation, and nutrients. Doctors collect CSF by performing a lumbar puncture, also called a spinal tap. Measuring the levels of proteins or other substances in CSF may be used to help diagnose Alzheimer's or other types of dementia.
• Blood tests. It is now possible for many doctors, dependent on state-specific availability reflecting U.S. Food and Drug Administration guidelines, 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. At present, blood test results alone should not be used to diagnose dementia, but may be taken into consideration along with other tests. However, the availability of these diagnostic tests is still limited.

Some of the tests and procedures used to diagnose dementia may not be covered by health insurance. Check with your insurance provider and talk with your health care team to determine what options may work best for you.

Early detection of symptoms is important as some causes can be successfully treated. However, in many cases, the cause of dementia is unknown and cannot be effectively treated. Still, obtaining an early diagnosis can help with managing the condition and planning ahead. In the early stages of dementia, it may be possible for people to continue with their everyday activities. As the disease progresses, people will need to adopt new strategies to help adjust.

Planning ahead may also include deciding what happens if and when the disease becomes more severe. Sometimes, a person with dementia will volunteer to donate their brain after they have died. Brain donation helps researchers study brain disorders such as Alzheimer’s disease and related dementias. By studying the brains of people who have died, researchers have already learned a great deal about how types of dementia affect the brain and how we might better treat and prevent them. But much more remains to be understood. 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. Learn more about brain donation.

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 primary care 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.

Dementia is the loss of cognitive functioning—the ability to think, remember, or reason—to such an extent that it interferes with a person's daily life and activities. These functions include memory, language skills, visual perception, problem solving, self-management, and the ability to focus and pay attention. 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 daily living (ADLs).

Age is the primary risk factor for developing dementia. For that reason, the number of people living with dementia could double in the next 40 years as the number of Americans age 65 and older increases to more than 88 million in 2050. Regardless of the form of dementia, the personal, economic, and societal demands can be devastating.

Dementia is not the same as age-related cognitive decline—when certain areas of thinking, memory, and information processing slow with age, but intelligence remains unchanged. Unlike dementia, age-related memory loss isn't disabling. Occasional lapses of forgetfulness are normal in elderly adults. While dementia is more common with advanced age (as many as half of all people age 85 or older may have some form of dementia), it is not an inevitable part of aging. Many people live into their 90s and beyond without any signs of dementia.

Dementia is also not the same as delirium, which is usually a short-term complication of a medical condition and most often can be treated successfully. Signs and symptoms of dementia result when once-healthy neurons (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.

Mild cognitive impairment (MCI) is a stage between normal cognitive changes that may occur with age and more serious symptoms that indicate dementia. Symptoms of MCI can include problems with thinking, judgment, memory, and language, but the loss doesn't significantly interfere with the ability to handle everyday activities. Symptoms of MCI include mild memory loss; difficulty with planning or organization; trouble finding words; frequently losing or misplacing things; and forgetting names, conversations, and events. Someone with MCI may be at greater risk of eventually developing Alzheimer's or another type of dementia, particularly if the degree of memory impairment is significant, but MCI does not always progress to dementia. Symptoms may remain stable for several years, and even improve over time in some people.

It is common to have more than one cause of dementia. Many people with dementia have both Alzheimer's disease and one or more closely related disorders that share brain scanning or clinical features (and sometimes both) with Alzheimer's disease. When a person is affected by more than one dementia disorder, the dementia can be referred to as a mixed dementia.

Autopsy studies of the brains of people who had dementia suggest that a majority of those age 80 and older probably had mixed dementia caused by Alzheimer's-related neurodegenerative processes, vascular disease-related processes, or another neurodegenerative condition. In fact, some studies indicate that mixed vascular-degenerative dementia is the most common cause of dementia in the elderly.

Researchers are still trying to understand the underlying disease processes involved in dementia. Scientists have some theories about mechanisms that may lead to different forms of dementia, but more research is needed to better understand if and how these mechanisms are involved.

Various disorders and factors contribute to dementia, resulting in a progressive and irreversible loss of neurons and brain functions. Currently, there are no cures for these neurodegenerative disorders.

Some specific causes of dementia disorders are explained below.

Alzheimer's disease (AD) is the most common cause of dementia in older adults. As many as five million Americans age 65 and older may have the disease. In most neurodegenerative diseases, certain proteins abnormally clump together and are thought to damage healthy neurons, causing them to stop functioning and die. In Alzheimer's disease, fragments of a protein called amyloid form abnormal clusters called plaques between brain cells, and a protein called tau forms tangles inside nerve cells.

It seems likely that damage to the brain starts a decade or more before memory and other cognitive problems appear. The damage often initially appears in the hippocampus, which is the part of the brain essential in forming memories. Ultimately, the plaques and tangles spread throughout the brain, and brain tissue significantly shrinks.

As Alzheimer's disease progresses, people experience greater memory loss and other cognitive difficulties. Problems can include wandering and getting lost, trouble handling money and paying bills, repeating questions, taking longer to complete daily tasks, and personality and behavior changes.

People are often diagnosed in this stage. Memory loss and confusion worsen, and people begin to have problems recognizing family and friends. They may be unable to learn new things, carry out multi-step tasks such as getting dressed, or cope with new situations. In addition, people at this stage may have hallucinations, delusions, and paranoia and may behave impulsively.

People with severe Alzheimer's disease cannot communicate and are completely dependent on others for their care. The person may be in bed most or all of the time as body functions shut down. Certain drugs can temporarily slow some symptoms of Alzheimer's from getting worse, but currently there are no treatments that stop the progression of the disease. 

Researchers have not found a single gene solely responsible for Alzheimer's disease; rather, multiple genes are likely involved. One genetic risk factor—having one form of the apolipoprotein E (APOE) gene on chromosome 19—does increase a person's risk for developing AD. People who inherit one copy of this APOE ε4 allele have an increased chance of developing the disease; those who inherit two copies of the allele are at even greater risk. (An allele is a variant form of a pair of genes that are located on a particular chromosome and control the same trait.) The APOE ε4 allele may also be associated with an earlier onset of memory loss and other symptoms. Researchers have found that this allele is associated with an increased number of amyloid plaques in the brain tissue of affected people.

Frontotemporal disorders are forms of dementia caused by a family of neurodegenerative brain diseases collectively called frontotemporal lobar degeneration. They primarily affect the frontal and temporal lobes of the brain, rather than the widespread shrinking and wasting away (atrophy) of brain tissue seen in Alzheimer's disease.

In these disorders, changes to nerve cells in the brain's frontal lobes affect the ability to reason and make decisions, prioritize and multitask, act appropriately, and control movement. Changes to the temporal lobes affect memory and how people understand words, recognize objects, and recognize and respond to emotions. Some people decline rapidly over two to three years, while others show only minimal changes for many years. People can live with frontotemporal disorders for two to 10 years, sometimes longer, but it is difficult to predict the. The signs and symptoms may vary greatly among individuals as different parts of the brain are affected. No treatment for curing or reversing frontotemporal disorders is currently available.

Clinically, FTD is classified into two main types of syndromes:

1. Behavioral variant frontotemporal dementia (bvFTD) involves changes in behavior, judgment, and personality. People with this disorder may have problems with cognition, but their memory may stay relatively intact. They may do impulsive things that are out of character or may engage in repetitive, unusual behaviors. People with bvFTD may say or do inappropriate things or become uncaring. Over time, language and/or movement problems may occur.
    
2. Primary progressive aphasia (PPA) involves changes in the ability to speak, understand, and express thoughts and/or words, and to write and read. Many people with PPA, though not all, develop symptoms of dementia. Problems with memory, reasoning, and judgment are not apparent at first but can develop and progress over time. Sometimes a person with PPA cannot recognize the faces of familiar people and common objects (semantic PPA). Other individuals have increasing trouble producing speech and may eventually be unable to speak at all (agrammatic PPA). PPA is a language disorder that is not the same as the problems with speech and ability to read and write (aphasia) that can result from a stroke.

Other types of frontotemporal disorders include:

• Corticobasal degeneration (CBD) involves progressive nerve-cell loss and atrophy of specific areas of the brain, which can affect memory, behavior, thinking, language, and movement. The disease is named after parts of the brain that are affected—the cerebral cortex (the outer part of the brain) and the basal ganglia (structures deep in the brain involved with movement). Not everyone who has CBD has problems with memory, cognition, language, or behavior. The disease tends to progress gradually, with early symptoms beginning around age 60. Some of the movement symptoms of CBD are similar to those seen in Parkinson's disease.
• Frontotemporal dementia with motor neuron disease (FTD/MND; also known as FTD-ALS) is a combination of behavioral variant frontotemporal dementia and the progressive neuromuscular weakness typically seen in amyotrophic lateral sclerosis (ALS). ALS is a neurodegenerative disease that attacks nerve cells responsible for controlling voluntary muscles (muscle action that can be controlled, such as in the arms, legs, and face). Symptoms of either disease may appear first, with other symptoms developing over time.
• Pick's disease is characterized by Pick bodies—masses comprised of the tau protein that accumulate inside nerve cells, causing them to appear enlarged or balloon-like. It is usually seen with bvFTD but sometimes with PPA. Some symptoms are similar to those of Alzheimer's disease, including loss of speech, changes in behavior, and trouble with thinking. However, while inappropriate behavior characterizes the early stages of Pick's disease, memory loss is often the first symptom of AD. Antidepressants and antipsychotics can control some of the behavioral symptoms of Pick's disease, but no treatment is available to stop the disease from progressing.
• Progressive supranuclear palsy (PSP) is a brain disease that can cause problems with thinking, memory, behavior, problem solving, and judgment. It also affects the control of eye movements, mood, speech, swallowing, vision, concentration, and language. Because certain parts of the brain that control movement are damaged, this disease shares some of the problems with movement seen in people with corticobasal degeneration and Parkinson's disease.

Lewy body dementia (LBD) is one of the most common causes of dementia after Alzheimer's disease and vascular disease. It typically begins after age 50, but can occur earlier. It involves abnormal protein deposits called Lewy bodies, which are balloon-like structures that form inside nerve cells. The abnormal buildup of the protein alpha-synuclein and other proteins causes neurons to work less effectively and die. Initial symptoms may vary, but over time, people with these disorders develop similar cognitive, behavioral, physical, and sleep-related symptoms.

Lewy body dementia includes two related conditions—dementia with Lewy bodies and Parkinson's disease dementia. In dementia with Lewy bodies, the cognitive symptoms are seen within a year of movement symptoms called parkinsonism (including tremor, difficulty with walking and posture, and rigid muscles). In Parkinson's disease dementia, the cognitive symptoms develop more than a year after movement problems begin.

1. Dementia with Lewy bodies (DLB) is one of the more common forms of progressive dementia. Neurons in the outer layer of the brain (cortex) and in the substantia nigra (a region involved with the production of dopamine) degenerate. Many neurons that remain contain Lewy bodies. Symptoms such as difficulty sleeping, loss of smell, and visual hallucinations often precede movement and other problems by as many as 10 years. Later in the course of DLB, some signs and symptoms are similar to Alzheimer's disease and may include memory loss, poor judgment, and confusion. Other signs and symptoms of DLB are similar to those of Parkinson's disease, including difficulty with movement and posture, a shuffling walk, and changes in alertness and attention. There is no cure for DLB, but there are drugs that control some symptoms.
2. Parkinson's disease dementia (PDD) can occur in people with Parkinson's disease, but not all people with Parkinson's disease will develop dementia. PDD may affect memory, social judgment, language, or reasoning. Autopsy studies show that people with PDD often have Lewy bodies in the cortex and other brain areas, and many have amyloid plaques and tau tangles like those found in people with Alzheimer's disease, though the causes of these similarities are not clear. The time from the onset of movement symptoms to the onset of dementia symptoms varies greatly from person to person. Risk factors for developing PDD include the onset of Parkinson's-related movement symptoms followed by mild cognitive impairment and REM sleep behavior disorder, which involves having frequent nightmares and hallucinations.

Vascular contributions to cognitive impairment and dementia (VCID) cause significant changes to memory, thinking, and behavior. Cognition and brain function can be significantly affected by the size, location, and number of brain injuries. Vascular dementia and vascular cognitive impairment arise as a result of risk factors that similarly increase the risk for cerebrovascular disease (stroke), including atrial fibrillation, hypertension, diabetes, and high cholesterol. Symptoms of VCID can begin suddenly and progress or subside during one's lifetime. VCID can occur along with Alzheimer's disease. People with VCID almost always have abnormalities in the brain on magnetic resonance imaging (MRI) scans. These include evidence of prior strokes, often small and asymptomatic, as well as scattered changes in the brain's “white matter," or the connecting “wires” of the brain that are critical for relaying messages between brain regions. Microscopic brain examination shows thickening of blood vessel walls called arteriosclerosis and thinning or loss of components of the white matter.

Forms of VCID include:

• Vascular dementia refers to progressive loss of memory and other cognitive functions caused by vascular injury or disease within the brain. Symptoms of vascular dementia may sometimes be difficult to distinguish from Alzheimer's disease. Problems with organization, attention, slowed thinking, and problem solving are all more prominent in VCID, while memory loss is more prominent in Alzheimer's.
• Vascular cognitive impairment involves changes with language, attention, and the ability to think, reason, and remember that are noticeable but are not significant enough to greatly impact daily life. These changes, caused by vascular injury or disease within the brain, progress slowly over time.
• Post-stroke dementia can develop months after a major stroke. Not everyone who has had a major stroke will develop vascular dementia, but the risk for dementia is significantly higher in someone who has had a stroke.
• Multi-infarct dementia is the result of many small strokes (infarcts) and mini-strokes. Language or other functions may be impaired, depending on the region of the brain that is affected. The risk for dementia is significantly higher in someone who has had a stroke. Dementia is more likely when strokes affect both sides of the brain. Even strokes that don't show any noticeable symptoms can increase the risk of dementia.
• Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an extremely rare, inherited disorder caused by a thickening of the walls of small- and medium-sized blood vessels, which reduces the flow of blood to the brain. CADASIL is associated with multi-infarct dementia, stroke, and other disorders. The first symptoms can appear in people between ages 20 and 40. CADASIL may have symptoms that can be confused with multiple sclerosis. Many people with CADASIL are undiagnosed.
• Subcortical vascular dementia (previously known as Binswanger's disease) involves extensive microscopic damage to the small blood vessels and nerve fibers that make up white matter. Some consider it an aggressive form of multi-infarct dementia. Cognitive changes include problems with short-term memory, organization, attention, decision making, and behavior. Symptoms tend to begin after age 60, and they progress in a stepwise manner. People with subcortical vascular disease often have high blood pressure, a history of stroke, or evidence of disease of the large blood vessels in the neck or heart valves.
• Cerebral amyloid angiopathy is a buildup of amyloid plaques in the walls of blood vessels in the brain. It is generally diagnosed when multiple tiny bleeds in the brain are discovered using MRI.

Many conditions that cause dementia-like symptoms can be halted or even reversed with the appropriate treatment.

• Normal pressure hydrocephalus is a buildup of cerebrospinal fluid in the brain. Elderly individuals with the condition usually have trouble walking and with bladder control before the onset of dementia. Normal pressure hydrocephalus can be treated or even reversed by implanting a shunt system to divert fluid from the brain.
• Nutritional deficiencies of vitamin B₁ (thiamine), caused by chronic alcoholism, and of vitamin B₁₂ can be reversed with treatment. People who have abused substances such as alcohol and recreational drugs sometimes display signs of dementia even after the substance abuse has stopped.
• Side effects of medications or drug combinations may cause cognitive impairment that looks like a degenerative or vascular dementia but which could reverse upon stopping these medications. 
• Vasculitis, an inflammation of brain blood vessels, can cause dementia after multiple strokes and may be treated with immunosuppressive medications.
• Subdural hematoma, or bleeding between the brain's surface and its outer covering (the dura), is common after a fall. Subdural hematomas can cause dementia-like symptoms and changes in mental function. With treatment, some symptoms can be reversed.
• Some non-malignant brain tumors can cause symptoms resembling dementia and recovery occurs following their removal by neurosurgery.
• Some chronic infections around the brain, so-called chronic meningitis, can cause dementia and may be treatable by drugs that kill the infectious agent.

Doctors have identified many other conditions that can cause dementia or dementia-like symptoms. The diseases have different symptoms that involve body and brain functions, and affect mental health and cognition.

• Argyrophilic grain disease is a common, late-onset degenerative disease that affects brain regions involved in memory and emotion. It causes cognitive decline and changes in memory and behavior, with difficulty finding words. The disease's signs and symptoms are indistinguishable from late-onset AD. Confirmation of the diagnosis can be made only at autopsy. 
• Creutzfeldt-Jakob disease (CJD) is a rare brain disorder that is characterized by rapidly progressing dementia. Scientists have found that infectious proteins called prions become misshapen and tend to clump together, which causes brain damage. Initial symptoms include impaired memory, judgment, and thinking, along with loss of muscle coordination and impaired vision. Some symptoms of CJD can be similar to symptoms of other progressive neurological disorders, such as Alzheimer's disease.
• Chronic traumatic encephalopathy (CTE) is caused by repeated traumatic brain injury (TBI) in some people with multiple concussions. People with CTE may develop dementia, poor coordination, slurred speech, and other symptoms similar to those seen in Parkinson's disease 20 years or more after the injury. Late-stage CTE is also characterized by brain atrophy and widespread deposits of tau in nerve cells. In some people, even just 5 to 10 years beyond the traumatic brain injury, behavioral and mood changes may occur. Dementia may not yet be present and the brain may not have started to shrink, but small deposits of tau are seen in specific brain regions at autopsy.
• Huntington's disease is an inherited, progressive brain disease that affects a person's judgment, memory, ability to plan and organize, along with other cognitive functions. Symptoms typically begin around age 30 to 40 years and include abnormal and uncontrollable movements (chorea) as well as problems with walking and lack of coordination. Cognitive problems worsen as the disease progresses, and problems controlling movement lead to complete loss of ability for self-care.
• HIV-associated dementia (HAD) can occur in people with human immunodeficiency virus, the virus that causes AIDS. HAD damages the brain's white matter and leads to a type of dementia associated with memory problems, social withdrawal, and trouble concentrating. People with HAD may develop movement problems as well. The incidence of HAD has dropped dramatically with the availability of effective antiviral therapies for managing the underlying HIV infections.
• Secondary dementias occur in people with disorders that damage brain tissue. Such disorders may include multiple sclerosis, meningitis, and encephalitis, as well as Wilson's disease (in which excessive amounts of copper cause brain damage). People with malignant brain tumors may develop dementia or dementia-like symptoms because of damage to their brain circuits or a buildup of pressure inside the skull.

Dementia is an umbrella term used to describe a range of neurological conditions affecting the brain that get worse over time.

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The following risk factors may increase a person's chance of developing one or more kinds of dementia. Some of these factors can be modified, while others cannot.

• Age—Advancing age is the best known risk factor for developing dementia.
• Hypertension—High blood pressure has been linked to cognitive decline, stroke, and types of dementia that damage the white matter regions of the brain. High blood pressure causes “wear-and-tear” to brain blood vessel walls called arteriosclerosis.
• Stroke—A single major stroke or a series of smaller strokes increases a person's risk of developing vascular dementia. A person who has had a stroke is at an increased risk of having additional strokes, which further increases the risk of developing dementia.
• Alcohol—Most studies suggest that regularly drinking large amounts of alcohol increases the risk of dementia. Specific dementias are associated with alcohol abuse, such as Wernicke-Korsakoff syndrome.
• Atherosclerosis—The accumulation of fats and cholesterol in the lining of arteries, coupled with an inflammatory process that leads to a thickening of the vessel walls (atherosclerosis), can lead to stroke, which raises the risk for vascular dementia.
• Diabetes—People with diabetes appear to have a higher risk for dementia. Poorly controlled diabetes is a risk factor for stroke and cardiovascular disease, which in turn increases the risk for vascular dementia.
• Down syndrome—Many people with Down syndrome develop symptoms of Alzheimer's disease by the time they reach middle age.
• Genetics—The chance of developing a genetically linked form of dementia increases when more than one family member has the disorder. In many dementias, there can be a family history of a similar disease. In some cases, such as with the FTDs, having just one parent who carries a mutation increases the risk of inheriting the condition. A very small proportion of dementia is inherited.   
• Head injury—An impact to the head can cause a traumatic brain injury (TBI). Certain types of TBI, or repeated TBIs, can cause dementia and other severe cognitive problems.
• Parkinson's disease—The degeneration and death of nerve cells in the brain in people with Parkinson's disease can cause dementia and significant memory loss.
• Smoking—Smoking increases the risk of developing cardiovascular diseases that slow or stop blood from getting to the brain.

As we age, our brains change, but Alzheimer’s disease and related dementias are not an inevitable part of aging. In fact, up to 40% of dementia cases may be prevented or delayed. It helps to understand what’s normal and what’s not when it comes to brain health.

Normal brain aging may mean slower processing speeds and more trouble multitasking, but routine memory, skills, and knowledge are stable and may even improve with age. It’s normal to occasionally forget recent events such as where you put your keys or the name of the person you just met.

Symptoms of Dementia or Alzheimer’s Disease

In the United States, 6.2 million people age 65 and older have Alzheimer’s disease, the most common type of dementia. People with dementia have symptoms of cognitive decline that interfere with daily life—including disruptions in language, memory, attention, recognition, problem solving, and decision-making. Signs to watch for include:

• Not being able to complete tasks without help.
• Trouble naming items or close family members.
• Forgetting the function of items.
• Repeating questions.
• Taking much longer to complete normal tasks.
• Misplacing items often.
• Being unable to retrace steps and getting lost.

Conditions That Can Mimic Dementia

Symptoms of some vitamin deficiencies and medical conditions such as vitamin B12 deficiency, infections, hypothyroidism (underactive thyroid), or normal pressure hydrocephalus (a neurological condition caused by the build-up of fluid in the brain) can mimic dementia. Some prescription and over-the-counter medicines can cause dementia-like symptoms. If you have these symptoms, it is important to talk to your health care provider to find out if there are any underlying causes for these symptoms.

How is Dementia Diagnosed?

A healthcare provider can perform tests on attention, memory, problem solving and other cognitive abilities to see if there is cause for concern. A physical exam, blood tests, and brain scans like a CT or MRI can help determine an underlying cause.

What To Do If a Loved One is Showing Symptoms

Talk with your loved one about seeing a health care provider if they are experiencing symptoms of Alzheimer’s dementia to get a brain health check up.

Be Empowered to Discuss Memory Problems

More than half of people with memory loss have not talked to their healthcare provider, but that doesn’t have to be you. Get comfortable with starting a dialogue with your health care provider if you observe any changes in memory, or an increase in confusion, or just if you have any questions. You can also discuss health care planning, management of chronic conditions, and caregiving needs.

Not sleeping enough can harm your health. It raises your risk of many diseases and disorders. A new study found this may include dementia.

The study looked at data from about 8,000 people in Britain starting at age 50 who were in a long-term health study. Participants were asked how many hours they slept per night. They reported on their sleep six times over a 30-year period. Some also wore a device that measured when they were active to check the accuracy of the reports.

During the study, 521 participants were diagnosed with dementia. They were about 77 years old on average at diagnosis. When researchers analyzed the data, they saw a link between short sleep and dementia.

People who slept six hours or less a night had a higher risk for dementia later in life. They were 30% more likely to be diagnosed with dementia than people who slept seven hours per night.

The researchers controlled for other factors that affect sleep. These included smoking, physical activity, and certain medical conditions.

This study doesn’t prove that a lack of sleep increases the risk of dementia. But it adds to others that suggest a connection. More studies are needed to understand why.

“While we cannot confirm that not sleeping enough actually increases the risk of dementia, there are plenty of reasons why a good night’s sleep might be good for brain health,” says Dr. Séverine Sabia of Inserm and University College London.

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 dementia. 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.

The different forms of age-related dementia, as well as many age-related neurodegenerative diseases, are thought to be caused by changes in various proteins. These diseases are called proteinopathies because they involve the abnormal buildup of specific proteins in the brain. Mutations in genes that provide instructions for making these proteins have been found to cause dementia in families. However, in the vast majority of affected individuals, dementia is not inherited, and the cause is unknown. Alzheimer's disease, frontotemporal disorders, and Lewy body dementia are proteinopathies.

In some dementias, changes in the tau protein cause it to form clumps inside nerve cells in the brain, which is believed to make the cells stop functioning properly and die. Disorders that are associated with the abnormal buildup of tau are called tauopathies.

In Alzheimer's disease, the tau protein aggregates (accumulates into abnormal clumps) and becomes twisted and tangled, forming fibers—neurofibrillary or tau tangles—inside neurons. Abnormal clumps (plaques) of the beta-amyloid protein are prominent in spaces between brain cells. Both plaques and tangles are thought to contribute to reduced function and nerve-cell death in AD and are the hallmarks of the disease.

Beta-amyloid plaques are also seen in some forms of LBD, cerebral amyloid angiopathy, and Parkinson's disease dementia. They are also common in elderly individuals who do not have dementia.

Some, but not all, forms of frontotemporal disorders are tauopathies. Other forms of these disorders are associated with the buildup of the protein TDP-43. A mutation in a gene called progranulin, and another in a gene called C9orf72, can cause frontotemporal disorders with accumulation of TDP-43 in nerve cells.

In other dementias and some brain disorders, the protein synuclein becomes misshapen and forms harmful clumps inside neurons in different brain regions. Disorders in which synuclein builds up inside neurons are called synucleinopathies. Changes in synuclein and/or its function are the basis of LBD and other disorders such as multiple system atrophy. Multiple system atrophy is a progressive neurodegenerative disorder characterized by a combination of symptoms that affect both the autonomic nervous system [the part of the nervous system that controls involuntary action such as blood pressure or digestion] and movement. These changes cause parkinsonism, a condition resembling Parkinson's disease.

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.

People with intellectual and developmental disabilities can also develop dementia as they age. Recognizing the symptoms can be difficult because they may be attributed to the person's disability. It’s important to consider a person’s existing ability and watch for changes over time that may signal dementia.

To diagnose dementia, doctors will first assess whether an individual has an underlying treatable condition such as abnormal thyroid function, vitamin deficiency, or normal pressure hydrocephalus that may relate to cognitive difficulties. Early detection of symptoms is important, as some causes can be treated. In many cases, the specific type of dementia may not be confirmed until after the person has died and the brain is examined.

An assessment may include:

• Medical history and physical exam—Assessing a person's medical and family history, current symptoms and medication, and vital signs can help the doctor detect conditions that might cause or occur with dementia. Some conditions may be treatable.
• Neurological evaluations—Examining balance, sensory response, reflexes, and other functions can help doctors identify signs of conditions that may affect the diagnosis or are treatable with drugs. Doctors also might use an electroencephalogram (EEG), a test that records patterns of electrical activity in the brain, to check for abnormal electrical brain activity.
• Brain scans—Computed tomography (CT) and magnetic resonance imaging (MRI) can detect structural abnormalities and rule out other causes of dementia. Positron-emission tomography (PET) can look for patterns of altered brain activity that are common in dementia. Advances in PET can detect amyloid plaques and tau tangles in AD.
• Cognitive and neuropsychological tests—These tests are used to assess memory, language skills, math skills, problem-solving, and other abilities related to mental functioning.
• Laboratory tests—Testing a person's blood and other fluids, as well as checking levels of various chemicals, hormones, and vitamin levels, can identify or rule out conditions that may contribute to dementia.
• Presymptomatic tests—Genetic testing can help some people who have a strong family history of dementia identify their own risks.
• Psychiatric evaluation—This evaluation can help determine if depression or another mental health condition is causing or contributing to a person's symptoms.

Guidelines prepared by the National Institute on Aging (NIA) and the Alzheimer's Association focus on three stages of Alzheimer's disease:

1. Dementia due to AD
2. Mild cognitive impairment (MCI) due to AD
3. Preclinical (presymptomatic) AD—presymptomatic identification is exclusively used as a research diagnosis at this point and has no relevance to routine clinical practice.

The guidelines also include biomarker tests used in studies to measure biological changes in the brain associated with Alzheimer's disease and criteria for documenting and reporting Alzheimer's-related changes observed during an autopsy.

There are currently no treatments to stop or slow dementia in neurodegenerative diseases. Some diseases that occur at the same time as dementia, such as diabetes and depression, can be treated. Other symptoms that may occur in dementia-like conditions can also be treated, although some symptoms may only respond to treatment for a period of time. A team of specialists—doctors, nurses, and speech, physical, and other therapists—familiar with these disorders can help guide patient care.

Therapists can help with maintaining physical movement, address speech and swallowing issues, and help people learn new ways to handle loss of skills with everyday tasks such as feeding oneself. It is important to educate family, friends, and caregivers about a loved one's medical issues. Also, in-person and online support groups available through many disease awareness and caregiver advocacy organizations can give families and other caregivers additional resources, as well as opportunities to share experiences and express concerns.

Medications are available to treat certain behavioral symptoms, as well as delusions, depression, muscle stiffness, and risk factors for vascular cognitive impairment such as high blood pressure. Always consult with a doctor, as some medications may make symptoms worse.

Most drugs for dementia are used to treat symptoms in AD. One class of drugs, cholinesterase inhibitors, can temporarily improve or stabilize memory and thinking skills in some people by increasing the activity of the cholinergic brain network—a subsystem in the brain that is highly involved with memory and learning. These drugs include donepezil, rivastigmine, and galantamine.

The drug memantine is in another class of medications called NMDA receptor antagonists, which prevent declines in learning and memory. Memantine may be combined with a cholinesterase inhibitor for added benefits. The U.S. Food and Drug Administration (FDA) approved the drug aducanumab (Aduhelm™) to reduce the building up harmful amyloid beta plaques.

There are no medications approved to treat or prevent frontotemporal disorders and most other types of progressive dementia. Sedatives, antidepressants, and other drugs used to treat Parkinson's and Alzheimer's symptoms may help manage certain symptoms and behavioral problems associated with the disorders.

Medicines available for managing Lewy body dementia are aimed at relieving symptoms such as gait and balance disturbances, stiffness, hallucinations, and delusions. Studies suggest that the cholinesterase inhibitor drugs for Alzheimer's disease may offer some benefit.

Some studies suggest that the cholinesterase inhibitors used to treat people with AD might improve cognitive, behavioral, and psychotic symptoms in people with Parkinson's disease dementia. Many of the medications used to treat the motor symptoms of PD worsen the cognitive problems. The FDA has approved rivastigmine (an Alzheimer's drug) to treat cognitive symptoms in PDD.

Vascular dementia is often managed with drugs that prevent strokes or reduce the risk of additional brain damage. Some studies suggest that drugs that improve memory in AD might benefit people with early vascular dementia. Treating the modifiable risk factors can help prevent additional stroke.

Dementia: Not an Inevitable Part of Aging

A recent survey revealed that nearly half of adults aged 40 years and older think they will likely develop dementia, such as Alzheimer’s disease.

The truth is dementia is not a normal or inevitable part of typical brain aging. It is also important to remember that as we get older, it is common to experience some cognitive decline with typical brain aging, such as subtle changes in memory, thinking, and reasoning. For example, you might not immediately remember where you left your car keys, but you can find them when retracing your steps, or you can’t think of the name of a person you just met; however, you remember meeting them. These subtle changes can be frustrating and should not be bad enough to affect your daily life.

Modifiable Risk Factors and Alzheimer’s Disease and Related Dementias

Modifiable risk factors are the lifestyle and behaviors that can reduce or increase a person’s chances of developing a disease. For example, there are modifiable risk factors that could reduce your risk of Alzheimer’s disease and related dementias (ADRD), slow its progression, or increase your risk of ADRD. Most modifiable risk factors for ADRD are related to cardiovascular disease and other chronic health conditions. They include hypertension, not getting enough physical exercise, obesity, diabetes, depression, smoking, hearing loss, and binge drinking. Maintaining a healthy lifestyle and managing related chronic conditions is good for your overall physical health, facilitates and improves brain health, and may help decrease the risk of dementia or slow its progression.

Antioxidants are a type of compound found in vegetables and fruits. They help protect your cells from a certain type of damage. Eating lots of produce can help lower your risk of heart disease and other health problems. A new study found that certain antioxidants in these foods may also reduce the risk for Alzheimer’s disease and other dementias.

Dementia, including Alzheimer’s disease, harms your ability to remember, think, and make decisions. Studies have found several lifestyle factors that may help lower the risk of getting dementia. These include eating a healthy diet, being physically active, and socializing with others. Getting enough sleep and doing activities that challenge your brain may also help.

Studies of antioxidants’ effects on dementia have had mixed results. Some have found that they protect the brain. Others have not. These studies asked people to remember what types of foods they’d eaten over a long period of time.

In a new study, researchers measured antioxidant levels in blood samples from more than 7,000 people. Participants were between the ages of 45 and 90. They were part of a nationwide study tracking their health over 16 years.

Blood levels of certain antioxidants were linked with a lower risk of developing dementia. These included lutein and zeaxanthin, which are found in green, leafy vegetables. They also included beta-cryptoxanthin, which is found in some orange-colored fruits.

“Further studies are needed to test whether adding certain antioxidants to the diet can help protect the brain from dementia,” says NIH’s Dr. May Beydoun, who led the study.

What Do We Know About Reducing Risk for Dementia?

The number of older Americans is rising, so the number of people with dementia is predicted to increase. However, some studies have shown that incidence rates of dementia — meaning new cases in a population over a certain period of time — have decreased in some locations, including in the United States. Based on observational studies, factors such as healthy lifestyle behaviors and higher levels of education may be contributing to such a decline. But the cause and effect is uncertain, and such factors need to be tested in a clinical trial to prove whether they can prevent dementia.

A review of published research evaluated the evidence from clinical trials on behavior and lifestyle changes to prevent or delay Alzheimer’s or age-related cognitive decline. The review found “encouraging but inconclusive” evidence for three types of behavioral changes (called interventions): physical activity, blood pressure control, and cognitive training. The findings mean that interventions in these areas are promising enough that researchers should keep studying them to learn more. Researchers continue to explore these and other interventions to determine whether — and in what amounts or forms — they might prevent dementia.

What Can You Do?

Although there is no effective treatment or proven prevention for Alzheimer’s and related dementias, in general, leading a healthy lifestyle may help address risk factors that have been associated with these diseases.

• Control high blood pressure. High blood pressure, or hypertension, has harmful effects on the heart, blood vessels, and brain, and increases the risk of stroke and vascular dementia. Treating high blood pressure with medication and healthy lifestyle changes, such as exercising and quitting smoking, may help reduce the risk of dementia.
• Manage blood sugar. Higher than normal levels of blood sugar, or glucose, can lead to diabetes and may increase the risk of heart disease, stroke, cognitive impairment, and dementia. Making healthy food choices, getting regular exercise, stopping smoking, and checking glucose levels can help manage blood sugar.
• Maintain a healthy weight. Being overweight or obese increases the risk for related health problems such as diabetes and heart disease. Being active and choosing healthy foods can help maintain a healthy weight.
• Eat a healthy diet. Aim for a mix of fruits and vegetables, whole grains, lean meats and seafood, unsaturated fats such as olive oil, low-fat or nonfat dairy products, and limited other fats and sugars.
• Keep physically active. Physical activity has many health benefits, such as helping to prevent being overweight and having obesity, heart disease, stroke, and high blood pressure. Aim to get at least 150 minutes of moderate-intensity physical activity each week.
• Stay mentally active. Lots of activities can help keep your mind active, including reading, playing board games, crafting or taking up a new hobby, learning a new skill, working or volunteering, and socializing.
• Stay connected with family and friends. Connecting with people and engaging in social activities can prevent social isolation and loneliness, which are linked to higher risks for cognitive decline and Alzheimer’s disease.
• Treat hearing problems. Hearing loss may affect cognition and dementia risk in older adults and can make it more difficult to interact with others. Protect your ears from loud sounds to help prevent hearing loss and use hearing aids if needed.
• Take care of your mental and physical health. This includes getting your recommended health screenings, managing chronic health issues such as depression or high cholesterol, and regularly checking in with your health care provider.
• Sleep well. Sleeping well is important for both your mind and body. Try to get seven to eight hours of sleep each night. Talk with your doctor if you are not getting enough sleep, sleeping poorly, or think you may have a sleep disorder.
• Prevent head injury. Take steps to prevent falls and head injury, such as fall-proofing your home and wearing shoes with nonskid soles that fully support your feet. Consider participating in fall prevention programs online or in your area. Also, wear seatbelts and helmets to help protect you from concussions and other brain injuries.
• Drink less alcohol. Drinking too much alcohol can lead to falls and worsen health conditions such as diabetes, high blood pressure, stroke, memory loss, and mood disorders. The National Institute on Alcohol Abuse and Alcoholism (NIAAA), part of the National Institutes of Health, recommends that men should not have more than two drinks a day and women only one.
• Stop tobacco use. At any age, stopping smoking can improve your health and lower the risk of heart attack, stroke, and lung disease.

Researchers cannot say for certain whether making the above lifestyle changes will protect against dementia, but these changes are good for your health and are all part of making healthy choices as you age.

Alpha-synuclein—The major protein present in abnormal clumps called Lewy bodies which are seen in the brains of people with Parkinson's disease and some dementias. Disorders in which alpha-synuclein accumulates inside nerve cells are called synucleinopathies.

Alzheimer's disease (AD)—The most common cause of dementia. Nearly all brain functions, including memory, movement, language, judgment, and behavior, are eventually affected. Alzheimer's disease is defined by observing high levels of amyloid-containing plaques and tau protein-containing neurofibrillary tangles in the brain.

Amyloid—A protein with beta-pleated sheets that aggregate to form the characteristic clumps (plaques) that appear in the brains of people with AD. Other proteins that form aggregates are tau proteins also seen in AD, and alpha-synuclein present in dementia with Lewy bodies and in Parkinson's Disease.

Biomarkers—Measurable biological signs in the living body that may indicate risk or progression of a disease and improve diagnosis.

Corticobasal degeneration—A progressive disorder characterized by abnormal buildup of the tau protein, nerve cell loss, and atrophy in multiple areas of the brain.

Dementia—A term for a condition that significantly interferes with daily life because of impaired thinking and memory.

Dementia with Lewy bodies—A type of Lewy body dementia that is a form of progressive dementia.

Frontotemporal disorders (FTD)—A group of dementias characterized by degeneration of nerve cells, especially those in the frontal and temporal lobes of the brain.

Lewy body dementia—A progressive dementia characterized by the presence of abnormal structures called Lewy bodies in the brain.

Mild cognitive impairment—a stage between normal cognitive changes that may occur with age and the more serious symptoms that indicate dementia

Mixed dementia—Dementia in which one form of dementia and another condition or dementia cause damage to the brain; for example, Alzheimer's disease and small vessel disease or vascular dementia.

Multi-infarct dementia—A type of vascular cognitive impairment and dementia caused by numerous small strokes in the brain.

Neurodegeneration—The progressive loss of nerve cell structure or function.

Neurofibrillary tangles—Bundles of twisted filaments largely made up of tau protein and found in nerve cells in the brains of people with AD and other types of dementia such as FTD.

Parkinson's disease dementia—A secondary dementia that can occur in people with advanced Parkinson's disease. Many people with Parkinson's have the amyloid plaques and neurofibrillary tangles found in Alzheimer's disease, but it is not clear if the diseases are linked.

Plaques—Abnormal clumps of amyloid protein that are found in large numbers in the brains of persons with Alzheimer's disease.

Tau—A protein that helps the functioning of microtubules, which are part of the cell's structural support that help deliver substances throughout the cell. In several dementia disorders, tau will twist into filaments that become tangles. Disorders associated with an accumulation of tau, such as frontotemporal dementia, are called tauopathies.

Vascular dementia—A type of dementia caused by brain damage from cerebrovascular or cardiovascular problems, usually strokes.