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Psychology EncyclopediaPsychological Dictionary: Kenneth John William Craik Biography to Jami (Mulla Nuruddin ʼAbdurrahman ibn-Ahmad Biography

A gradual deterioration of mental functioning affecting all areas of cognition, including judgment, language, and memory.

Dementia generally occurs in the elderly, although it can appear at any age. Several substantial studies have been done to determine its prevalence, and in 1991 a major study was conducted which found that dementia occurred in just over 1 percent of the population aged 65 to 74; in approximately 4 percent in ages 75 to 84; and more than doubling to 10.14 percent in persons 85 and over. Other studies have concluded that many as 47 percent of people over 85 suffer from some form of dementia. Prevalence rates tend to be comparable between the sexes and across sociocultural barriers, such as education and class. It is also worth noting that, despite what is often commonly thought, dementia is not an inevitable consequence of aging.

Researchers have identified many types of dementia, including dementia resulting from Alzheimer's disease, vascular dementia, substance induced dementia, dementia due to multiple etiologies, dementia due to other general medical conditions, and dementia not otherwise specified. More than half of the persons diagnosed with dementia are classified as having dementia resulting from Alzheimer's disease. This type of dementia occurs in more than half of dementia cases in the United States. There is no definitive method in diagnosing this kind of dementia until after the patient's death and an autopsy can be performed on the brain. Alzheimer-related dementia is characterized by slow deterioration in the initial stages, but the rate of cognitive loss speeds up as the disease progresses. Patients with this type of dementia can generally be expected to live eight years.

Vascular dementia is the second most common type of dementia and is caused by damage to the blood vessels that carry blood to the brain, usually by stroke. Because the area of the brain that is affected differs from person to person, the pattern of cognitive deterioration in this type of dementia is unpredictable. Other diseases that can cause dementia include human immunodeficiency virus (HIV), Parkinson's disease, Huntington's disease, Pick's disease, and Creutzfeldt-Jakob disease. The kind of dementia induced by these diseases is known as subcortical, meaning they affect mainly the interior structures of the brain, as opposed to cortical dementia (Alzheimer's and vascular) which affect the outer layers of the brain. Many of these subcortical diseases have been known for some time to result in dementia, but HIV-related dementia has only recently been described and diagnosed. Recent studies have indicated that between 29 to 87 percent of people with AIDS show significant signs of dementia.

Generally speaking, dementia has a gradual onset and can take different routes in different people. All sufferers, however, are eventually impaired in all areas of cognition. Initially, dementia can appear in memory loss, which may result in being able to vividly remember events from many years past while not being able to remember events of the very recent past. Other symptoms of dementia are agnosia, which is the technical term for not being able to recognize familiar objects, facial agnosia, the inability to recognize familiar faces, and visiospatial impairment, the inability to locate familiar places.

Along with cognitive deterioration, sufferers of dementia often experience related emotional disorders as they recognize their deterioration and experience anxiety about its continuation and worsening. Typical among reactions are depression, anxiety, aggression, and apathy. Psychologists are uncertain to what extent these symptoms are direct results of dementia or simply responses to its devastation. Dementia progressively deteriorates the brain and eventually sufferers are completely unable to care for themselves and, ultimately, the disease results in death.

Further Reading

Cooper, James W. Jr. "The Effects of Dementia." American Druggist (April 1993): 59.

Crystal, Howard. "Treating Severe Clinical Memory Disorders." Newsweek (3 May 1993): S6.

"Dementia: When You Suspect a Loved One's Problem." Mayo Clinic Health Letter (November 1995): 6

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