What Is Dementia? Symptoms, Types, and Diagnosis
Dementia is the loss of cognitive functioning—thinking, remembering, and reasoning—and behavioral abilities 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 living.
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.
While dementia is more common as people grow older (up to half of all people age 85 or older may have some form of dementia), it is not a normal part of aging. Many people live into their 90s and beyond without any signs of dementia. One type of dementia, frontotemporal disorders, is more common in middle-aged than older adults.
The causes of dementia can vary, depending on the types of brain changes that may be taking place. Alzheimer's disease is the most common cause of dementia in older adults. Other dementias include Lewy body dementia, frontotemporal disorders, and vascular dementia. It is common for people to have mixed dementia—a combination of two or more types of dementia. For example, some people have both Alzheimer's disease and vascular dementia.
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 types of disorders. They include:
Other types of progressive brain disease include:
- Vascular contributions to cognitive impairment and dementia
- 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, certain medical conditions can cause serious memory problems that resemble dementia. These problems should go away once the conditions are treated. 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
- Head injury, such as a concussion from a fall or accident
- Thyroid, kidney, or liver problems
Doctors have 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 (CTE), caused by repeated traumatic brain injury
- HIV-associated dementia (HAD)
The overlap in symptoms of various dementias can make it hard to get an accurate diagnosis. But a proper diagnosis is important to get the right treatment. Seek help from a neurologist—a doctor who specializes in disorders of the brain and nervous system—or other medical specialist who knows about dementia.
How is Dementia Diagnosed?
To diagnose dementia, doctors first assess whether a person has an underlying treatable condition such as abnormal thyroid function, normal pressure hydrocephalus, or a vitamin deficiency 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 a person has may not be confirmed until after the person has died and the brain is examined.
A medical assessment for dementia generally includes:
- Medical history. Typical questions about a person's medical and family history 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.
- Physical exam. Measuring blood pressure and other vital signs may help physicians detect conditions that might cause or occur with dementia. Some conditions may be treatable.
- Neurological tests. Assessing balance, sensory response, reflexes, and other cognitive functions helps identify conditions that may affect the diagnosis or are treatable with drugs.
What Tests are Used to Diagnose Dementia?
The following procedures also may be used to diagnose dementia:
- Cognitive and neuropsychological tests. These tests are used to assess memory, problem solving, language skills, math skills, 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 vitamins, can help find or rule out possible causes of symptoms.
- 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 known gene defect. 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.
For More Information About Dementia
NIA Alzheimer’s and related Dementias Education and Referral (ADEAR) Center
The National Institute on Aging’s ADEAR Center offers information and free print publications about Alzheimer’s disease and related dementias for families, caregivers, and health professionals. ADEAR Center staff answer telephone, email, and written requests and make referrals to local and national resources.
This content is provided by the National Institute on Aging (NIA), part of the National Institutes of Health. NIA scientists and other experts review this content to ensure that it is accurate, authoritative, and up to date.
Content reviewed: December 31, 2017