Alzheimer disease

Introduction
Stages of the disease
Neuropathology
- Neuritic plaques and neurofibrillary tangles
- Hyperinsulinemia
- Genetic variants
Treatment
Early detection
Lifestyle factors and prevention

References & Edit History Quick Facts & Related Topics

Images & Videos

How physical activity can slow Alzheimer disease

Digital illustration of a neuron network in blue with scattered yellow-orange amyloid plaques, representing Alzheimer disease pathology.

At a Glance

Alzheimer disease summary

Quizzes

Diseases, Disorders, and More: A Medical Quiz

44 Questions from Britannica’s Most Popular Health and Medicine Quizzes

Related Questions

Are amyloid plaques and tau tangles a cause or a consequence of Alzheimer disease?
At what ages does familial early-onset Alzheimer disease usually appear?
Can neuritic plaques and neurofibrillary tangles occur in healthy older adults?
How can an APP gene defect increase amyloid beta deposition in the brain?
How can fMRI help researchers study Alzheimer disease risk in APOE4 carriers?
How common is Alzheimer disease among dementia cases in people over age 60?
How could infection be related to amyloid plaque formation in Alzheimer disease?
How does Alzheimer disease affect the ability to retain new information?
How does Alzheimer disease damage and reduce the size of the brain?
How does abnormal tau protein form neurofibrillary tangles?
How does early-onset familial Alzheimer disease differ from more common late-onset Alzheimer disease?
How does neuron loss affect communication between brain cells in Alzheimer disease?
How does reduced acetylcholine contribute to memory problems in Alzheimer disease?
How is the TOMM40 gene used to estimate the age of Alzheimer disease onset?
How might amyloid beta act as a natural antibiotic in the brain?
How might early hippocampal hyperactivity contribute to later Alzheimer disease?
What are neuritic plaques in Alzheimer disease?
What are neurofibrillary tangles in Alzheimer disease?
What are the earliest signs and symptoms of Alzheimer disease?
What are the preclinical mild cognitive impairment and dementia stages used in Alzheimer disease diagnosis?
What changes in hippocampal activity have been observed in young APOE4 carriers?
What happens during the late stages of Alzheimer disease?
What material forms the center of a neuritic plaque?
What proportion of early familial Alzheimer disease cases are linked to the APP gene?
What roles do the CD33 PICALM and CD2AP genes have in Alzheimer disease research?
Where in the brain are neurofibrillary tangles commonly found?
Which brain cells are lost during the progression of Alzheimer disease?
Which chromosomes contain genetic defects linked to early-onset familial Alzheimer disease?
Which neurotransmitters are reduced in Alzheimer disease?
Why are neuritic plaques and neurofibrillary tangles examined during an Alzheimer disease autopsy?
Why do some Alzheimer disease symptoms become worse at night?
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External Websites

National Health Service - Alzheimer's Disease
Live Science - Alzheimer's Disease: Brain Changes, Symptoms and Treatment
National Library of Medicine - Alzheimer Disease
Verywell Health - Alzheimer's Disease
MSD Manual - Professional Version - Alzheimer Disease

Britannica Websites

Articles from Britannica Encyclopedias for elementary and high school students.

Alzheimer Disease - Children's Encyclopedia (Ages 8-11)
Alzheimer disease - Student Encyclopedia (Ages 11 and up)

Alzheimer disease

pathology

Also known as: Alzheimer’s disease

Written and fact-checked by

Britannica Editors

Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....

Britannica Editors

Last updated

Nov. 13, 2026 •History

Alzheimer disease, degenerative brain disorder that develops in mid-to-late adulthood. It results in a progressive and irreversible decline in memory and a deterioration of various other cognitive abilities. The disease is characterized by the destruction of nerve cells and neural connections in the cerebral cortex of the brain and by a significant loss of brain mass. The disease was first described in 1906 by German neuropathologist Alois Alzheimer. By the early 21st century it was...

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