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 performing the tasks of daily life. Dementia can occur to anyone at any age from an injury or from oxygen deprivation, although it is most commonly associated with aging. It is the leading cause of institutionalization of older adults.

Description

The definition of dementia has become more inclusive over the past several decades. Whereas earlier descriptions of dementia emphasized memory loss, the last three editions of the professional's diagnostic handbook, Diagnostic and Statistical Manual of Mental Disorders(also known as the DSM) 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, braindiseases, tumors, or other disorders— it is quite common in older people. The prevalence of dementia increases rapidly with age; it doubles every five years after age 60. Dementia affects only 1% of people aged 60–64 but 30%–50% of those older than 85. About four to five million persons in the United States are affected by dementia as of 2002. Surveys indicate that dementia is the condition most feared by older adults in the United States.

Causes

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's disease(AD), frontal lobe dementia (FLD), and Pick's disease. FLD is dementia caused by a disorder (usually genetic) that affects the front portion of the brain, and Pick's disease is a rare type of primary dementia that is characterized by a progressive loss of social skills, language, and memory, leading to personality changes and sometimes loss of moral judgment.
• 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. (An infarct is an area of dead tissue caused by obstruction of the circulation.)
• 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's and Parkinson's disease, but researchers do not yet know whether dementia with Lewy bodies is a distinct type of dementia or a variation of Alzheimer's or Parkinson's 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). Spirochetes are certain kinds of bacteria, and prions are protein particles that lack nucleic acid.
• 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 B ₁₂deficiency. Dementia related to these conditions is often reversible.