Dementia Health Article

Definition

Dementia is not a specific disorder or disease. It is a syndrome (group of symptoms) associated with a progressive loss of memory and other intellectual functions that is serious enough to interfere with the tasks of daily life. Dementia can occur to anyone at any age from an injury or oxygen deprivation, although it is most commonly associated with aging.

Description

The definition of dementia has become more inclusive over the past several decades. Whereas earlier descriptions of dementia emphasized memory loss, the last two editions of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R in 1987 and DSMIV in 1994) define dementia as an overall decline in intellectual function, including difficulties with language, simple calculations, planning and judgment, and motor (muscular movement) skills as well as loss of memory. Although dementia is not caused by aging itself—most researchers regard it as resulting from injuries, infections, brain diseases, tumors, or other disorders—it is quite common in older people. Common estimates are that over 15% of people in North America over the age of 65 suffer from dementia, and 40% of people over 80. Surveys indicate that dementia is the condition most feared by older adults in the United States.

Dementia can be caused by nearly forty different diseases and conditions, ranging from dietary deficiencies and metabolic disorders to head injuries and inherited diseases. The possible causes of dementia can be categorized as follows:

• Primary dementia. These dementias are characterized by damage to or wasting away of the brain tissue itself. They include Alzheimer disease (AD), Pick disease, and frontal lobe dementia (FLD).
• Multi-infarct dementia (MID). Sometimes called vascular dementia, this type is caused by blood clots in the small blood vessels of the brain. When the clots cut off the blood supply to the brain tissue, the brain cells are damaged and may die.
• Lewy body dementia. Lewy bodies are areas of injury found on damaged nerve cells in certain parts of the brain. They are associated with Alzheimer and Parkinson disease, but researchers do not yet know whether dementia with Lewy bodies is a distinct type of dementia or a variation of Alzheimer or Parkinson disease.
• Dementia related to alcoholism or exposure to heavy metals (arsenic, antimony, bismuth).
• Dementia related to infectious diseases. These infections may be caused by viruses (HIV, viral encephalitis); spirochetes (Lyme disease, syphilis); or prions (Creutzfeldt-Jakob disease).
• Dementia related to abnormalities in the structure of the brain. These may include a buildup of spinal fluid in the brain (hydrocephalus); tumors; or blood collecting beneath the membrane that covers the brain (subdural hematoma).

Dementia may also be associated with depression, low levels of thyroid hormone, or niacin or vitamin (B12) deficiency. Dementia related to these conditions is often reversible.