Dementia Health Article

Definition

The term dementia refers to symptoms, including changes in memory, personality, and behavior, that result from a change in the functioning of the brain. These declining changes are severe enough to impair the ability of a person to perform a function or to interact socially. This operating definition encompasses 70–80 different types of dementia. They include changes due to diseases (Alzheimer's and Creutzfeld-Jakob diseases), changes due to a heart attack or repeated blows to the head (as suffered by boxers), and damage due to long-term alcohol abuse.

Dementia is not the same thing as delirium or mental retardation. Delirium is typically a brief state of mental confusion often associated with hallucinations. Mental retardation is a condition that usually dates from childhood and is characterized by impaired intellectual ability; mentally retarded individuals typically have IQ (intelligence quotient) scores below 70 or 75.

Description

The absent-mindedness and confusion about familiar settings and tasks that are hallmarks of dementia used to be considered as part of a typical aging pattern in the elderly. Indeed, dementia historically has been called senility. Dementia is now recognized not to be a normal part of aging. The symptoms of dementia can result from different causes. Some of the changes to the brain that cause dementia are treatable and can be reversed, while other changes are irreversible.

Demographics

An estimated two million people in the United States alone have severe dementia. Up to five million more people in the United States have milder forms of cognitive impairment of the dementia type. The elderly are most prone to dementia, particularly those at risk for a stroke. The historical tendency of women to live longer than men has produced a higher prevalence of dementia in older women. However, women and men are equally prone to dementia. Over age 80, more than 20% of people have at least a mild form of dementia.

Causes and symptoms

Dementia is especially prominent in older people. The three main irreversible causes are Alzheimer's disease, dementia with Lewy bodies, and multi-infarct dementia (also called vascular dementia).

Degenerative forms of dementia are long lasting (chronic) and typically involve a progressive loss of brain cell function. In disorders like Alzheimer's and Creutzfeld-Jakob diseases, this can involve the presence of infectious agents that disturb the structure of proteins that are vital for cell function. Other forms of dementia are chemically based. For example, Parkinson's disease involves the progressive loss of the ability to produce the neurotransmitter dopamine. Interrupted transmission of nerve impulses causes the progressive physical and mental deterioration. Huntington's disease is an inherited form of dementia that occurs when neurons (brain cells) degenerate.

Alzheimer's disease is the most common cause of dementia. The progressive death of nerve cells in the brain is associated with the formation of clumps (amyloid plaques) and tangles of protein (neurofibrillary tangles) in the brain. The loss of brain cells with time is reflected in the symptoms; minor problems with memory become worse, and impairment in normal function can develop. Alzheimer's patients also have a lower level of a chemical that relays nerve impulses between nerve cells. As the brain damage progresses, other complications can ensue from the damage and these can prove fatal. Put another way, people die with Alzheimer's, not from it.

Dementia resulting from the abnormal formation of protein in the brain (Lewy bodies) is the second most common form of dementia in the elderly. It is unclear whether these structures are related to the brain abnormalities noted in Alzheimer's patients. Lewy body formation differs from Alzheimer's in that the speed of brain functions is affected more so than memory.

In multi-infarct dementia, blood clots can dislodge and impede the flow of blood in blood vessels in the brain. The restricted flow of blood can lead to death of brain cells and a stroke.

Dementias that are caused by the blockage of blood vessels are generally known as vascular dementia. This type of dementia can sometimes be reversed if the blood-vessel blockage can be alleviated. In contrast, the dementia associated with Alzheimer's disease is non-reversible.

Less common causes of dementia include Binwanger's disease (another vascular type of dementia), Parkinson's disease, Pick's disease, Huntington's disease, Creutzfeldt-Jakob disease, and acquired immunodeficiency syndrome (AIDS).

A study published in 2002 documented a link between elevated levels of an amino acid called homocysteine in the blood and the risk of developing dementia, likely vascular dementia. As homocysteine concentration can be modified by diet, the finding holds the potential that one risk factor for dementia may be controllable.

Symptoms of dementia include repeatedly asking the same question; loss of familiarity with surroundings; increasing difficulty in following directions; difficulty in keeping track of time, people, and locations; loss of memory; changes in personality or emotion; and neglect of personal care. Not everyone displays all symptoms. Indeed, symptoms vary based on the cause of the dementia. Also, symptoms can progress at different rates in different people.