Dementia refers to a loss of cognitive function (cognition) due to changes in the brain caused by disease or trauma. The changes may occur gradually or quickly; and how they occur may determine whether dementia is reversible or irreversible.
Cognition is the act or process of thinking, perceiving, and learning. Cognitive functions that may be affected by dementia include the following:
Decision making, judgment
Dementia also may result in behavioral and personality changes, depending on the area(s) of the brain affected.
Some dementia is reversible and can be cured partially or completely with treatment. The degree of reversibility often depends on how quickly the underlying cause is treated.
Irreversible dementia is caused by an incurable condition (e.g., Alzheimer's disease). Patients with irreversible dementia are eventually unable to care for themselves and may require round-the-clock care.
Incidence and Prevalence
An estimated 2 million people in the United States suffer from severe dementia and another 1 to 5 million people experience mild to moderate dementia. Five to eight percent of people over the age of 65 have some form of dementia and the number doubles every 5 years over age 65.
The prevalence of dementia has increased over the past few decades, either because of greater awareness and more accurate diagnosis, or because increased longevity is creating a larger population of elderly, which is the age group most commonly affected.
The greatest risk factor for dementia is advanced age. Inheriting the genes associated with Alzheimer's or Huntington's disease is a risk factor. Untreated infectious and metabolic disease and substance abuse also can lead to dementia.
Alzheimer’s (AHLZ-high-merz) disease is a progressive brain disorder that gradually destroys a person’s memory and ability to learn, reason, make judgments, communicate and carry out daily activities. As Alzheimer’s progresses, individuals may also experience changes in personality and behavior, such as anxiety, suspiciousness or agitation, as well as delusions or hallucinations.
Although there is currently no cure for Alzheimer’s, new treatments are on the horizon as a result of accelerating insight into the biology of the disease. Research has also shown that effective care and support can improve quality of life for individuals and their caregivers over the course of the disease from diagnosis to the end of life.
Alzheimer’s is the most common form of dementia, a group of conditions that all gradually destroy brain cells and lead to progressive decline in mental function. Vascular dementia, another common form, results from reduced blood flow to the brain’s nerve cells. In some cases, Alzheimer’s disease and vascular dementia can occur together in a condition called "mixed dementia." Other causes of dementia include frontotemporal dementia, dementia with Lewy bodies, Creutzfeldt-Jakob disease and Parkinson’s disease.
Alzheimer’s disease advances at widely different rates. The duration of the illness may often vary from 3 to 20 years. The areas of the brain that control memory and thinking skills are affected first, but as the disease progresses, cells die in other regions of the brain. Eventually, the person with Alzheimer’s will need complete care. If the individual has no other serious illness, the loss of brain function itself will cause death.