Medically reviewed on Aug 27, 2018
What Is It?
Dementia is a pattern of mental decline caused by different diseases or conditions. Most commonly, dementia occurs when brain nerve cells (neurons) die, and connections between neurons are interrupted. These disruptions have a variety of causes and usually cannot be reversed.
Alzheimer's disease causes over 60% of all dementias. Vascular disease, such as stroke, is the second most common cause.
Lewy body disease, which causes neurons in the brain to degenerate, causes another 20% of dementias.
Other conditions that can cause dementia include:
Lewy body disease
Traumatic head injury
Acquired immunodeficiency syndrome
Degenerative diseases, such as Huntington's disease and Pick's disease
Many other rare degenerative conditions
In rare cases, dementia is caused by a treatable condition, and it may be partially or entirely reversed if the condition is diagnosed and treated early:
Adverse reactions to drugs
Infections, such as syphilis or fungal meningitis
Metabolic conditions, such as deficiencies of vitamin B12 or thyroid hormone
In the developed nations, about 15% of people older than 65 are thought to have dementia.
Symptoms of dementia emerge slowly, get worse over time and limit the person's ability to function.
The first symptom of dementia is memory loss. Everyone has memory lapses from time to time. However, the memory loss of dementia is greater and affects your ability to function. For example, forgetting where you put your car key is normal. Forgetting how to use the key is a possible symptom of dementia.
Often, someone with dementia does not realize that he or she has a problem. Instead, family members recognize that something is wrong.
Along with memory loss, a person with dementia may have trouble with complex mental tasks. They may have difficulty balancing a checkbook, driving, knowing what day it is and learning new things. They may be inattentive, and display poor judgment. Their mood and behavior also may change.
As the disorder progresses, the person may have difficulty speaking in full sentences. They may not recognize their surroundings, or other people. They may have problems with personal care, such as bathing. In some cases, a person with dementia may see or hear things that are not (hallucinations and delusions). They may get very agitated, may withdraw from other people.
The doctor will ask when memory problems started and how quickly they got worse. This information, together with the person's age, can help suggest a likely diagnosis. For example:
If the person is elderly and has had consistently worsening memory and other problems for several years, a doctor may suspect Alzheimer's disease.
If symptoms got worse rapidly, then Creutzfeldt-Jakob disease may be a likely cause.
If the person has had a prior stroke or is at higher risk of stroke, the doctor will consider vascular dementia as the underlying cause.
However, the exact cause of dementia in any individual can often be difficult to determine.
To diagnose dementia, a doctor looks to see if a person's memory gets progressively worse, along with at least one of the following:
Difficulty understanding or using language
The inability to perform a purposeful act or sequence of motor activities
The inability to recognize familiar objects or people
Difficulty doing such complex tasks as planning or organizing
Doctors test people by testing memory and attention. A commonly used tool to screen for dementia is the Mini Mental State Exam. It consists of 11 short assessments, such as asking the person what day and year it is or have the person count backward from 100 by sevens (100, 93, 86, etc.). If the person answers correctly, dementia is less likely.
Laboratory tests can narrow down the possible causes. Some tests include:
Magnetic resonance imaging (MRI) or computed tomography (CT) scans – These create pictures of structures inside the head (similar to the way X-rays create images of bones). The pictures can reveal brain tumors and stroke. If these tests do not show any major abnormalities, the diagnosis could be Alzheimer's disease.
Positron emission tomography (PET) scans – Increasingly, these scans are being used to detect Alzheimer's disease, and conditions that can turn into Alzheimer's disease. They are not yet widely available.
Blood tests – These are done to help judge overall health and also to determine if vitamin B12 deficiency or very low levels of thyroid hormone may be contributing to the decreased mental functioning.
Lumbar puncture (spinal tap) – This test is rarely needed to evaluate dementia. Occasionally, your doctor may want to be certain that fluid pressure around the brain is normal. Also laboratory testing on a sample of spinal fluid can make sure there is no infection. Researchers are studying proteins in the spinal fluid to see if certain patterns can detect specific causes of dementia, or can predict the outlook (prognosis).
In most cases, dementia gets worse and cannot be cured. A person with dementia may live for months, years or decades, depending on the cause of the dementia and whether the person has other medical conditions.
In the rare cases in which dementia is caused by a treatable condition, such as infection, metabolic disorder or depression, the dementia usually is reversed after treatment.
Most of the causes of dementia cannot be prevented. Good personal health habits and medical care, however, can prevent some types of dementia. Here are some things you can do:
Dementia caused by Alzheimer's disease and stroke – Many of the same practices that reduce the risk of heart disease and stroke also reduce the risk of Alzheimer's disease. Monitor and control your blood pressure and cholesterol, exercise every day, and eat a balanced diet with plenty of fruits and vegetables to maintain a healthy body weight, try to maintain a healthy weight, avoid tobacco.
Alcohol-related dementia – Limit the amount of alcohol you drink.
Traumatic dementia – Avoid head injury by always using seat belts, helmets and other protective equipment.
Some infection-related dementias – Avoid high-risk sexual behavior.
Vitamin-deficiency dementia – Make sure your diet has enough B vitamins, especially vitamin B12. Your doctor may want to order a blood test for B12 level.
Hormone-related dementia – Your doctor may want to order a blood test called TSH (thyroid stimulating hormone) to make sure your thyroid is functioning properly.
Keeping your mind active and your body fit may help to prevent mental decline and reduce or postpone memory loss. If you get daily physical exercise and continue to challenge your brain throughout life, you can help to protect your brain against mental decline.
Sometimes the cause of dementia can be reversed, such as vitamin B12 deficiency or an underactive thyroid. Treating these conditions may improve the dementia. Other reversible factors that can contribute to symptoms include overuse of alcohol and depression.
People with vascular dementia may show less mental decline if their blood pressure is controlled, they stop smoking, lower LDL ("bad" cholesterol), exercise regularly and maintain a healthy weight.
In some people, medications for Alzheimer's may help with behavioral symptoms and perhaps slow down the mental decline. They may delay the need for placement into a nursing home. Acetylcholinesterase inhibitors, such as donepezil (Aricept), galantamine (Razadyne) and rivastigmine (Exelon), can be prescribed for mild to moderate Alzheimer's dementia. Memantine (Namenda) is approved for moderately severe Alzheimer's dementia.
These same medications are sometimes used to treat the dementia associated with Lewy body disease.
However, many people do not improve at all with medication or improve only a little.
Depending on the cause of the dementia, several specialists may be involved in care, including neurologists, psychologists, psychiatrists or geriatric doctors. Nurses and social workers play a very important role in care.
Here are some easy to implement aspects of care that help ease symptoms:
Familiar surroundings, people and routines, because too much change can cause confusion and agitation
Bright, active environments to help focus the person's attention and keep him or her oriented to the environment
Safe environments so that the person cannot be hurt or get lost if he or she wanders away
Physical exercise to improve balance and general good health
Appropriate therapies, including music, art and occupational therapy, to provide stimulation and improve control of muscles
When To Call a Professional
Call your doctor if you or a loved one is having difficulty with any of the following:
Learning and remembering new information
Handling complex tasks, such as preparing a meal
Reasoning, such as knowing how to organize shopping
Orientation, such as knowing the day of the week or the time of day
Language, including finding words to express thoughts
A person with dementia may also exhibit the following types of behaviors:
Changes in mood behavior, such as irritability
Placing everyday objects in odd places, such as putting a hat in the microwave
Forgetting the day, month, time or location
Loss of desire to initiate activities or be as active as usual
The outlook for dementia depends on the cause and can vary by individual. For example, early treatment of dementia caused by a vitamin deficiency can lead to full recovery of memory. If stroke is the cause, the person's memory loss can remain stable for years.
Drugs may slow the rate of decline for some people with Alzheimer's disease.
In most cases, however, the disorder gradually gets worse. Depending on the cause, the person's age, general health and the availability of treatments, life expectancy can be as short as a few months or as long as 15 to 20 years.
Learn more about Dementia
IBM Watson Micromedex
Symptoms and treatments
Mayo Clinic Reference
National Institute of Neurological Disorders and Stroke
P.O. Box 5801
Bethesda, MD 20824
American Geriatrics Society
The Empire State Building
350 Fifth Ave.
New York, NY 10118
225 North Michigan Ave.
Chicago, IL 60601-7633
Alzheimer's Disease Education and Referral Center (ADEAR)
National Institute on Aging
P.O. Box 8250
Silver Spring, MD 20907-8250
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.