Dementia is a general term used to describe a decline in mental function that is severe enough to interfere with daily living. Dementia is not a specific disease. It is a group of symptoms that can affect thinking, memory, reasoning, personality, mood and behavior.
Dementia develops when the parts of the brain that are involved with learning, memory, decision-making, and language are affected by any of various infections or diseases. The most common cause of dementia is Alzheimer's disease. However, there are numerous other known causes of dementia, such as vascular dementia, dementia with Lewy bodies, and dementia due to Parkinson’s disease and others. The condition of dementia is not a normal part of aging.
One common misbelief about memory loss is that it always means a person has dementia. There are many causes of memory loss. Memory loss alone doesn’t necessarily confirm a diagnosis of dementia. It’s also true that some memory loss is normal as a person ages (some neurons in the brain naturally die as we age). However, this type of memory loss is not disabling.
Dementia is considered a late-life disease because it tends to develop mostly in elderly people. About five to eight percent of all people over the age of 65 have some form of dementia, and this number doubles every five years above that age. It is estimated that as many as half of people 85 or older have dementia.
Dementias are often broken down into two main categories -- Alzheimer type or non-Alzheimer type. Dementias of the Alzheimer’s disease type are defined by the symptoms of memory loss plus impairment in other brain functions, such as language function (aphasia); inability to move the muscles associated with speech (lips tongue and jaw; apraxia); or perception, visual or other inabilities to recognize speech or name objects (agnosias).
Non-Alzheimer dementias include the frontotemporal lobar degenerations, which are further broken down into two main types. One type primarily affects speech. An example is primary progressive aphasia syndromes. The other type is defined by changes in behavior, including lack of feeling, emotion, interest or concern (apathy); loss of a “social filter” (disinhibition); personality change and loss of executive functions (such as the ability to organize and plan ahead). In both of these frontotemporal lobe dementias, memory loss is relatively mild until later in the course of the disease.
Other non-Alzheimer’s disease dementias include vascular disorders (multiple strokes), dementia with Lewy bodies, Parkinson's dementia, and normal pressure hydrocephalus.
Dementia is caused by damage to the brain. There are many causes of dementia. The causes of dementia can be generally grouped as follows:
Alzheimer's disease accounts for 50 percent to 70 percent of all dementias. However, many patients with Alzheimer's disease also have damage from other vascular brain disease, such as from mini strokes. Patients with more than one brain condition present that cause dementia are considered to have "mixed" dementia. Frontotemporal lobar degenerations, of which there are several types, account for a substantial number of dementias, especially among people in their 50s and 60s. Dementia with Lewy bodies has also been diagnosed with increasing frequency in recent years. These patients have clinical signs of Parkinsonism as well as dementia, though the connection between dementia and Parkinson's disease is still not completely understood.
Early symptoms of dementia include :
Signs that dementia is getting worse include:
The symptoms mentioned above are general symptoms of dementia. Each person diagnosed with dementia has different symptoms, depending on what area of the brain is damaged. Additional symptoms and/or unique symptoms occur with specific types of dementia.
Confirming the diagnosis of dementia can be difficult due to the many diseases and conditions that cause it as well as because its symptoms are common to many other illnesses. However, doctors are able to make the diagnosis based on the results of personal medical history, review of current symptoms, neurological (brain) and cognitive (thinking) tests, laboratory tests, imaging tests (CT, MRI, PET scans) and by interacting with the patient.
Current general symptoms that would indicate dementia are, by definition, a decline in such mental functions as memory, thinking, reasoning, personality, mood or behavior that are severe enough to interfere with the ability to accomplish everyday tasks. Patients undergo mental function testing (memory tests, language skills, reasoning and judgment evaluations, problem-solving tasks, other thinking skill tests) to identify problems in these areas. Interviews with family members and/or close friends who may have noticed changes in these areas are helpful as well.
Laboratory tests rule out other diseases and conditions as the cause of dementia, such as thyroid problems and vitamin B12 deficiency. Similarly, brain scans can look for signs of a stroke or tumor that may be the source of the dementia. A PET scan can determine if amyloid proteins are present in the brain, a marker for Alzheimer’s disease.
Oftentimes, neurologists and geriatricians assist in making the diagnosis.
First, it’s important to understand the difference in the terms treatable, reversible, and curable. All or almost all forms of dementia are treatable, in that medication and supportive measures are available to help manage symptoms in patients with dementia. However, most types of dementia remain incurable or irreversible and treatment results in only modest benefits.
Some dementias disorders, however, may be successfully treated, with patient returning to normal after treatment. These dementias are ones caused by:
Dementias that are not reversible, but may still be at least partially responsive to medications currently available for memory loss or behavior-based problems include:
Drugs approved for the most common form of dementia, Alzheimer’s disease, are discussed below. These drugs are also used to treat people with some of the other forms of dementia.
These two classes of drugs affect different chemical processes in the brain. Both classes have been shown to provide some benefit in improving or stabilizing memory function in some patients. Although none of these drugs appear to stop the progression of the underlying disease, they may slow it down.
If other medical conditions are causing dementia or co-exist with dementia, the appropriate drugs used to treat those specific conditions are prescribed.
Although dementia cannot be prevented, living a health-focused life might influence risk factors for certain types of dementia. Keeping blood vessels clear of cholesterol buildup, maintaining normal blood pressure, controlling blood sugar, staying at a healthy weight – basically, staying as healthy as one can – can keep the brain fueled with the oxygen and nutrients it needs to function at its highest possible level. Specific healthful steps you can take include:
Make an appointment with your doctor if you or your friends and family see changes in:
Last reviewed by a Cleveland Clinic medical professional on 03/18/2019.