View the Health Heart Book

Free

E-Newsletters

Subscribe to receive the latest updates on health topics. About our newsletters

  • Housecall
  • Alzheimer's caregiving
  • Living with cancer
Connect with others who've been there. Share stories. Learn. Join Mayo Clinic's
online community.

Causes

By Mayo Clinic staff

Alzheimer's caregiving newsletter

Subscribe to our Alzheimer's caregiving newsletter to stay up to date on Alzheimer's topics.

Scientists believe that for most people, Alzheimer's disease results from a combination of genetic, lifestyle and environmental factors that affect the brain over time.

Less than 5 percent of the time, Alzheimer's is caused by specific genetic changes that guarantee a person will develop the disease.

While the causes of Alzheimer's are not yet fully understood, its effect on the brain is clear. Alzheimer's disease damages and kills brain cells. A brain affected by Alzheimer's disease has many fewer cells and many fewer connections among surviving cells than does a healthy brain.

As more and more brain cells die, Alzheimer's leads to significant brain shrinkage. When doctors examine Alzheimer's brain tissue under the microscope, they see two types of abnormalities that are considered hallmarks of the disease:

  • Plaques. These clumps of a protein called beta-amyloid may damage and destroy brain cells in several ways, including interfering with cell-to-cell communication. Although the ultimate cause of brain-cell death in Alzheimer's isn't known, abnormal processing of beta-amyloid is a prime suspect.
  • Tangles. Brain cells depend on an internal support and transport system to carry nutrients and other essential materials throughout their long extensions. This system requires the normal structure and functioning of a protein called tau. In Alzheimer's, threads of tau protein twist into abnormal tangles, leading to failure of the transport system. This failure is also strongly implicated in the decline and death of brain cells.
Risk factors Symptoms
References
  1. Middleton LE, et al. Promising strategies for prevention of dementia. Archives of Neurology. 2009;66:1210.
  2. Preventing Alzheimer's disease and cognitive decline. National Institutes of Health State-of-the-Science Conference Statement. April 26-28, 2010. http://consensus.nih.gov/2010/docs/alz/ALZ_Final_Statement.pdf. Accessed Oct. 28, 2010.
  3. Rusanen M, et al. Heavy smoking in midlife and long-term risk of Alzheimer disease and vascular dementia. Archives of Internal Medicine. In press. Accessed Oct. 28, 2010.
  4. Alternative treatments. Alzheimer's Association. http://www.alz.org/alzheimers_disease_alternative_treatments.asp Accessed Nov. 5, 2010.
  5. Scarmeas N, et al. Physical activity, diet, and risk of Alzheimer disease. JAMA. 2009;302:627.
  6. Alzheimer's disease fact sheet. National Institute on Aging. http://www.nia.nih.gov/NR/rdonlyres/7DCA00DB-1362-4755-9E87-96DF669EAE20/13991/ADFactSheetFINAL2510.pdf. Accessed Oct. 29, 2010.
  7. Grabowski TJ. Clinical manifestations and diagnosis of Alzheimer's disease http://www.uptodate.com/home/index.html. Accessed Oct. 30, 2010.
  8. Press D, et al. Treatment of dementia. http://www.uptodate.com/home/index.html. Accessed Oct. 30, 2010.
  9. Shadlen M-F, et al. Risk factors for dementia. http://www.uptodate.com/home/index.html. Accessed Oct. 30, 2010.
  10. What is Alzheimer's? Alzheimer's Association. http://www.alz.org/alzheimers_disease_what_is_alzheimers.asp. Accessed Nov. 4, 2010.
  11. Prevention. Alzheimer's Association. http://www.alz.org/research/science/alzheimers_prevention_and_risk.asp. Accessed Oct. 31, 2010.
  12. Essentials of a diagnostic workup. Alzheimer's Association. http://www.alz.org/professionals_and_researchers_14902.asp. Accessed Oct. 31, 2010.
  13. Basics of Alzheimer's disease. Alzheimer's Association. http://www.alz.org/national/documents/brochure_basicsofalz_low.pdf. Accessed October 31, 2010.
  14. Late stage care. Alzheimer's Association. http://www.alz.org/national/documents/brochure_latestage.pdf. Accessed Nov. 2, 2010.
  15. Strobel, G. Noisy response greets revised diagnostic criteria for AD. Alzheimer Research Forum. http://www.alzforum.org/new/detail.asp?id=2522. Accessed Nov. 3, 2010.
  16. Neurological tests and procedures. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/misc/diagnostic_tests.htm. Accessed Nov. 3, 2010.
  17. Caring for a person with Alzheimer's disease. National Institute on Aging. http://www.nia.nih.gov/NR/rdonlyres/E0F45395-A473-4B26-8F7E-86F4314405CE/0/CaringGuide.pdf. Accessed Nov. 4, 2010.
  18. Medical foods. Alzheimer's Association. http://www.alz.org/national/documents/statements_medicalfoods.pdf. Accessed Nov. 19, 2010.
  19. Is it really approved? Food and Drug Administration. http://www.fda.gov/downloads/ForConsumers/ConsumerUpdates/UCM143301.pdf. Accessed Nov. 19, 2010.
DS00161 Jan. 18, 2011

© 1998-2012 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.com," "EmbodyHealth," "Enhance your life," and the triple-shield Mayo Clinic logo are trademarks of Mayo Foundation for Medical Education and Research.

Print Share Reprints

Advertisement


Text Size: smaller largerlarger