Key features

  • Historically considered the most common cause of dementia, accounting for 50 to 70 percent of all cases.
  • Hallmark symptom is insidious-onset impairment in ability to remember new information.
  • May be associated with early impairment in language and visuospatial or executive function.
  • Impaired daily activities.
  • Largely normal neurological exam.
  • Brain images of individuals with Alzheimer's show increased hippocampal and overall brain atrophy, but absolute levels of shrinkage have not yet been quantified and standardized.
  • Growing evidence suggests that with advancing age, dementia that "looks like" Alzheimer's is increasingly likely due to a combination of Alzheimer's pathology and other pathologies known as "mixed dementia."


Learn more about the treatment and management of Alzheimer's disease.


  • The classic neuropathological signs of Alzheimer's disease are amyloid plaques and neurofibrillary tangles.
  • Plaques consist largely of the protein fragment beta-amyloid. This fragment is produced from a "parent" molecule called amyloid precursor protein.
  • Tangles consist of tau, a protein normally involved in maintaining the internal structure of the nerve cell. While tau is normally modified by phosphorylation, or the attachment of phosphate molecules, excessive phosphorylation appears to contribute to tangle formation and prevents the protein from carrying out its normal functions.
  • Oxidative stress, or damage to cellular structures by toxic oxygen molecules called free radicals, is also regarded as a pathology characteristic of Alzheimer's.
  • Individuals with Alzheimer's typically experience brain inflammation.
  • Many of the oldest patients with Alzheimer's show signs of cerebrovascular disease in addition to "classic" Alzheimer's neuropathology.

For your patients and families: What is Alzheimer's?