Alzheimer’s disease is a progressive, neurodegenerative disease characterized in the brain by abnormal clumps (amyloid plaques) and tangled bundles of fibers (neurofibrillary tangles) composed of misplaced proteins. Age is the most important risk factor for Alzheimer’s disease. The number of people with the disease doubles every 5 years beyond age 65.

Alzheimer’s disease is characterized by the development of multiple cognitive deficits manifested by:

  • Memory impairment (impaired ability to learn new information or to recall previously learned information)
  • And one (or more) of the following cognitive disturbances:
  • Deterioration of language may be manifested by difficulty producing the names of individuals and objects (aphasia)
  • An impaired ability to carry out motor activities (such as combing their hair) despite intact motor abilities, sensory function and comprehension of the required task (apraxia)
  • A failure to recognize or identify objects despite intact sensory function (agnosia)
  • A disturbance in executive functioning (e.g., planning, organizing, sequencing, abstracting)

The cognitive deficits above each cause significant impairment in social or occupational functioning and represent a significant decline from a previous level of functioning. The course is characterized by gradual onset and continuing cognitive decline. The deficits do not occur exclusively during the course of a delirium.