What Is Dementia?

Dementia is a general, umbrella term for the loss of brain function that affects memory, thinking, language, judgment and behavior. The loss is significant enough to disrupt daily life.

Dementia affects people differently and produces different symptoms, depending on which area or areas of the brain are damaged. Memory loss is a common symptom of dementia, but if it is the only symptom, it is not enough to make a diagnosis. In order to be diagnosed with dementia, two or more brain functions must be significantly impaired. Brain functions that may be affected by dementia include:

  • Learning/Memory
  • Language function
  • Perceptual-motor function
  • Social cognition
  • Executive function
  • Complex attention

Dementia is a progressive condition, which means that it worsens over time. Scientists have not yet identified a way to reverse the effects of dementia, but medication can help with the symptoms. Some conditions, like reactions to medications or vitamin deficiencies, may cause symptoms similar to dementia. In these cases, the symptoms can often improve with treatment.

Causes of Dementia

Dementia is caused by physical changes in the brain. These changes may include damage to nerve cells and their connections in the brain.

Common Types of Dementia

Progressive dementias

Alzheimer’s disease

Alzheimer’s disease is the most common cause of dementia among older adults, and represents 60 to 80% of all dementia cases. It is a progressive disease with no cure, but it is possible to slow the progression of symptoms with treatment.

The greatest risk factor is getting older. Most people with Alzheimer’s usually develop symptoms after age 65, and the risk doubles about every five years after that time. Sometimes symptoms begin before age 65, which is known as Early-Onset Alzheimer’s disease.

Alzheimer’s is diagnosed by identifying plaques and tangles in the brain. Plaques are clumps of a protein called beta-amyloid, and tangles are fibrous tissues made up of tau protein. Experts believe that plaques damage the neurons and connections in the brain.

Stages of Alzheimer’s Disease

The disease usually follows a progressive pattern. However, each person is unique and may display symptoms differently. Monitoring the stages of disease helps with decision-making when caring for someone with Alzheimer’s disease.

Preclinical stage. Changes in the brain can begin years before any signs or symptoms of the disease appear.

Mild, early stage. Symptoms at this stage include mild forgetfulness that may seem like typical age-related changes. During the early stage, a person with Alzheimer’s disease might not be aware of their memory impairment, but friends or family will begin to notice. Realizing that something is wrong is usually a gradual process for both the patient and their family.

While symptoms are mild, people with early-stage Alzheimer’s disease may appear healthy and may be able to live independently, although they may have increasing difficulty with daily routines and activities. Showing early-stage symptoms while still being able to function independently is called Mild Cognitive Impairment (MCI), and can last for years. When the disease progresses, cognitive decline can include different types of problems:

  • Difficulty remembering a name or recalling recent events
  • Trouble remembering where they put a valuable object
  • Taking longer than normal to complete routine, daily tasks
  • Difficulty staying organized, forming organized thoughts or making plans
  • Trouble managing money or paying bills
  • Trouble navigating in a new place or with complex spatial directions
  • Difficulty initiating tasks independently or making sound judgments
  • Increased anxiety or restlessness

Moderate, middle stage. This is typically the longest stage, and usually lasts many years.  Common symptoms include:

  • Increasing difficulty remembering events
  • Problems learning new things or coping with new situations
  • Difficulty with problem-solving, complex tasks or planning events
  • Trouble reading, writing and working with numbers
  • Tendency to repeat questions, statements or movements
  • Increased confusion with time and place
  • Needing assistance with daily activities and becoming moody or withdrawn
  • Behavioral problems such as hallucinations, paranoia or delusions
  • Becoming more restless, agitated, anxious or fearful, especially in the late afternoon or at night

During the middle stage, some people also experience:

  • Physical changes
  • Sleep problems
  • Tendency to wander away from home
  • Aggressive or inappropriate behavior, including outbursts

Severe, late stage. People with severe Alzheimer’s disease cannot communicate coherently and are completely dependent on others for their care:

  • Requires daily assistance with personal care
  • Loses many physical abilities, including walking, sitting and eating
  • May be able to say some words or phrases, or make noises, but cannot have a conversation
  • May lose bowel and bladder control
  • Is unaware of recent experiences and of their surroundings
  • May experience weight loss, difficulty swallowing or seizures

Vascular Dementia

Vascular dementia is a progressive condition resulting in loss of memory and other cognitive functions. This type of dementia is caused by vascular injury or disease within the brain. When blood vessels that supply blood to the brain are damaged, small blood clots can form which prevent oxygen from reaching the brain tissue. This may cause a stroke or may damage the fibers in the deep portion of the brain. The most common symptoms include difficulty with problem-solving, reasoning or judgment, slowed thinking, and loss of focus or organization. Often, these symptoms are more noticeable than memory loss.

Lewy Body Dementia

Lewy body dementia (LBD) is a disease that affects the areas of the brain responsible for thought, movement, mood and behavior, visual perception, and regulating sleep and alertness. It is one of the more common types of progressive dementia. With LBD, abnormal, balloon-like clumps of a protein called alpha-synuclein, or Lewy bodies, build up in the brain. Lewy body dementia includes two subtypes: dementia with Lewy bodies and Parkinson’s disease dementia. Common signs and symptoms include problems with focus and attention, uncoordinated or slow movement, tremors, rigidity (parkinsonism), visual hallucinations, and acting out while sleeping.

Frontotemporal Dementia

Frontotemporal dementia (FTD) is a group of diseases caused by the breakdown of nerve cells and their pathway connections in the frontal and temporal lobes of the brain. These areas of the brain control personality, behavior and language. With FTD, people experience dramatic changes in personality including socially inappropriate, impulsive or indifferent behavior. Some people may lose their ability to use language properly. FTD is the most common cause of dementia in people younger than age 60, and approximately 60% of people with this type of dementia are 45 to 64 years old. It is often initially misdiagnosed as a psychiatric condition or Alzheimer’s disease.

Mixed Dementia

This diagnosis is made when someone has a combination of two or more types of dementia. It is most common in people older than age 75. Many older adults with dementia have a combination of causes, such as, Alzheimer's disease and vascular dementia.

Dementia-like Conditions That Can Be Reversed

Certain causes of dementia, or dementia-like symptoms, can be reversed with treatment. These include:

Infections and Immune Disorders

It is possible to develop dementia-like symptoms from a fever or other side effects of the body’s attempt to fight off an infection. Certain immune disorders, like multiple sclerosis, which are caused by the body’s immune system attacking nerve cells, can also cause dementia.

Metabolic Problems and Endocrine Abnormalities

Thyroid problems, low blood sugar (hypoglycemia), having too little or too much sodium or calcium, or problems absorbing vitamin B-12 can cause dementia-like symptoms or other personality changes.

Nutritional Deficiencies

Not drinking enough liquids (dehydration) can cause dementia symptoms. Vitamin deficiencies from poor diet or other problems can also cause these symptoms. Some of the most common vitamin deficiencies include: vitamin B-1 (thiamin), a deficiency which is common in people with chronic alcoholism, B-6, B-12, E and copper.

Medication Side Effects

Side effects of certain medications, a reaction to a medication, or an interaction of several medications, can cause dementia-like symptoms.

Subdural Hematomas

A subdural hematoma is the result of an injury, often caused by a fall which can be common among the elderly population. Bleeding occurs between the surface of the brain and the covering over the brain, which can cause dementia-like symptoms.

Brain Tumors

Damage caused by a brain tumor can cause dementia, although this is rare.

Normal-Pressure Hydrocephalus

This condition is caused by enlarged ventricles in the brain. It can result in walking problems, urinary difficulty and memory loss.

Sleep Disorders

Other Disorders Linked to Dementia

Huntington's Disease

This is an inherited, progressive brain disease caused by a genetic mutation. It causes certain nerve cells in the brain and spinal cord to waste away. Signs and symptoms usually appear around age 30 or 40, and include a severe decline in thinking (cognitive) skills.

Traumatic Brain Injury (TBI)

This condition is most often caused by repetitive head trauma, and causes different symptoms depending on which part of the brain has been injured. Common dementia signs and symptoms caused by TBI include depression, explosiveness, memory loss and impaired speech. TBI can also cause parkinsonism. Because of the risk of repeated head injury, people including boxers, football players or soldiers might develop TBI, and sometimes symptoms do not appear until years after the trauma has occurred.

Creutzfeldt-Jakob Disease

This is a rare, fatal brain disorder that most often occurs in people without known risk factors. Creutzfeldt-Jakob disease usually has no known cause but can be inherited. It may be due to deposits of infectious proteins called prions, or it may also be caused by exposure to diseased brain or nervous-system tissue, such as from a cornea transplant. Signs and symptoms usually appear after age 60.

Parkinson's Disease

Many people with Parkinson's disease eventually develop dementia symptoms. This is known as Parkinson's disease dementia, which is a subtype of Lewy body dementia.

HIV-Associated Dementia (HAD)

This type of dementia occurs when the HIV virus spreads to the brain. Symptoms of HIV-associated dementia include memory loss, difficulty thinking, concentrating or speaking clearly, lack of interest in activities, and gradual loss of motor skills.

Chronic Traumatic Encephalopathy (CTE)

CTE is a rare, degenerative brain disorder caused by repeated traumatic brain injury. The diagnosis is made only at autopsy by studying sections of the brain. Experts are still trying to understand how repeated head traumas, including quantifying how many head injuries and the severity of those injuries, might contribute to the changes in the brain that result in CTE.

How Is Dementia Diagnosed?

To diagnose dementia, doctors assess the patient’s cognitive abilities and evaluate how those abilities have changed over time. This process requires a good history of the problems, including when they were first noticed and how they have progressed. The patient may not be the best source of historical information, so typically a family member or someone else will provide significant parts of the history of the patient’s changes over time. The patient’s medical history also is important because past medical conditions can play a significant role in cognitive changes the patient may be experiencing.

Doctors use the information from the assessment to come up with a working diagnosis of whether dementia is present, the severity of the cognitive problems, and the underlying causes and contributors.

A medical assessment for dementia generally includes:

Medical history

Typical questions about medical and family history might include: how and when symptoms began and were first noticed, changes in behavior or personality and whether the progression of problems has been fast or slow, continuous and gradual or stepwise in progression. Other important information to be collected may include past medical conditions, past and recent life events, medications taken and changes in medications.

Physical exam

Measuring vital signs, including blood pressure, can help physicians detect conditions that might cause or occur with dementia. Some conditions may be treatable.

Neurological exam

Assessing vision, hearing, speech, strength, sensation, reflexes, coordination, balance and gait, in addition to memory testing, can help identify the underlying problems and help suggest additional testing and initial treatments.

Laboratory tests

Blood tests to measure electrolytes, kidney function, liver function, blood counts, hormone levels and nutrition may identify problems that, in some cases, can be addressed to help improve cognition. Occasionally, a spinal tap (lumbar puncture) is used to evaluate the cerebrospinal fluid.

Brain scans

Computerized tomography (CT) or magnetic resonance imaging (MRI) scans can provide helpful information about brain structure and past medical events that can affect memory function. These scans can also make sure there are no ongoing contributors such as stroke, bleeding, tumor or hydrocephalus.  Functional imaging studies, including positron emission tomography (PET) and single-photon emission computerized tomography (SPECT) scans, can help to determine brain metabolism, dopamine activity and the amount of beta-amyloid plaques present in the brain.

Neuropsychological testing

Comprehensive neurocognitive testing can help to determine, in detail, which cognitive areas are working and which are not. This testing can also provide insight into underlying causes and contributions from mood disorders like depression or anxiety.

Psychiatric evaluation

In some cases, a formal psychiatric evaluation can be helpful to evaluate and treat underlying depression, anxiety or other psychiatric issues.

Genetic testing

In some cases, genetic tests can be used to assess a specific cause of dementia or assess the risk of developing dementia. It is important to talk with a genetic counselor before and after testing to understand the goals, limitations and implications of the results.

Treatment for Dementia

Each patient is unique, and a treatment plan is created based on a patient’s individual needs and working diagnosis. While medications may be helpful in many cases, often they help improve some of the symptoms rather than fix or cure the root cause of dementia. Treatment is divided into three broad categories: lifestyle modifications, caregiver support and medications.

Lifestyle Modifications

“Use it or lose it.” Staying active and engaged, socially, mentally and physically, is a core principle of treating cognitive problems. Finding activities that are interesting and keep the brain engaged will help preserve brain function. The activities need to be appropriate for the individual patient. Good choices should provide some challenge while also allowing opportunities for success and enjoyment. Social outings, physical exercise, games, tasks, chores and time outside can all be helpful.

“You break it, you pay for it.” Good sleep and good diet can help maintain and improve memory. Poor or insufficient sleep, social stress or conflict, excessive alcohol use, taking medications incorrectly and falls with injury can all worsen memory performance, both in the short term and over time.

Caregiver Support

In early stages of mild cognitive impairment, support may simply include having additional eyes and ears to make sure the patient is performing well and staying engaged socially, mentally and physically. As cognition dysfunction progresses and dementia becomes more severe, a patient will need help understanding medical and financial decisions, making the living situation safe and appropriate, and taking medications regularly. As dementia progresses, caregivers will need to provide increasing help with the activities of daily living.

Cognitive changes in dementia can include changes in emotions and the handling of daily situations. Irritability, anxiety and depression can happen early in the course of cognitive decline. With some types of dementia, it is common for patients to exhibit emotional outbursts, hallucination and delusions. Caregivers can help to reduce the impact of these emotional episodes by providing a good reality check for the patient and helping restore calm. While medications may be necessary to help support these efforts, caregivers also play a critical role in helping patients cope with daily challenges and emotional changes.


Medications can be helpful, to some extent, to ease symptoms and preserve memory.

Drugs That May Change Disease Progression

In 2021, the FDA approved a new medication (Aducanumab, Aduhelm™) for Alzheimer’s disease. It is the first medication to target beta-amyloid, the abnormal protein that is found in plaques in the brains of patients with Alzheimer’s disease. The plaques are thought to contribute to neuron dysfunction and cell death, so experts suggest that clearing the beta-amyloid plaques may improve cognition and slow down progression of the disease.

Scientists believe this medication will work best for patients with mild dementia or mild cognitive impairment with confirmed evidence of a buildup of beta-amyloid plaques in the brain. Currently, the medication is complicated to deliver and is not well-covered by most insurance plans. It requires extensive surveillance with repeated MRI studies to ensure there are no adverse reactions. However, the medication is a promising first step to address the biological changes in the brain associated with Alzheimer’s disease. In July 2021, the first patient in Houston was infused with the medication (1st Houston patient receives new Alzheimer drug at Memorial Hermann).

Drugs That May Improve Symptoms of Memory Decline

Cholinesterase inhibitors (donepezil, rivastigmine, galantamine). These medications prevent the breakdown of acetylcholine, a neurotransmitter in the brain that is important for memory, learning and other tasks. These medications can help improve short-term memory and attention. While originally FDA-approved for use in patients with Alzheimer’s disease, they are now also used for patients with different types of dementia. Although generally well-tolerated, some patients may experience gastrointestinal side effects (nauseas, vomiting, diarrhea, loss of appetite) and cardiac side effects (bradycardia or slow heart rate).

Glutamate regulators (memantine). These medications regulate glutamate, a neurotransmitter involved in learning and information processing. It can help memory and can help stabilize mood. Though generally well-tolerated, it can cause side effects including tiredness, dizziness and confusion.

Drugs That May Improve Behavioral and Psychological Symptoms

Orexin receptor antagonists (Suvorexant). This medication is used to treat insomnia for people with mild to moderate Alzheimer’s disease. It can be quite expensive.

Antidepressant medications. Several classes of antidepressant medications are used to help patients with mood symptoms associated with cognitive decline, including mood stabilization, motivation and anxiety. Some of these medications may also help with sleep and appetite.

Antiseizure medications. While uncommon, some patients with dementia have seizure events. Antiseizure medications can help reduce or eliminate those events. In some cases, these medications can also help stabilize mood and reduce agitation and aggression.

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