Overview of Dementia

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
  • Memory
  • Spatial orientation
  • Thinking, reasoning
  • Verbal communication

Dementia also may result in behavioral and personality changes, depending on the area(s) of the brain affected.

Types of Dementia

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 of Dementia

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 has created a larger population of elderly, which is the age group most commonly affected. In September 2009, it was estimated that as many as 35 million people throughout the world have some type of dementia.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 02 Jan 2000

Last Modified: 24 May 2011