What is Alzheimer's Disease?

Written by Wendy Leonard, MPH | Published on August 8, 2014
Medically Reviewed by George Krucik, MD, MBA on August 8, 2014

What Is Alzheimer's Disease?

The most common cause of dementia is Alzheimer’s disease (AD). AD is a progressive and irreversible brain disorder. The actual cause of AD is unknown. AD slowly damages a person’s memory, judgment, reasoning skills, personality, autonomy, and bodily functions. 

The disease specifically affects several components of the brain. These include:

  • a gradual loss of brain cells (neurons)
  • damage to neurons so they no longer function properly
  • the loss of neural connections (synapses) where messages are passed from neuron to neuron

Forgetfulness: A Normal Part of Aging?

It’s normal to sometimes forget things. As we age, it often takes longer to remember words or names, or where we left our glasses. These forgetful moments don’t necessarily indicate dementia. In fact, scientists have found that healthy older adults perform just as well as their young counterparts on complex and learning tests if given extra time to complete.  

There’s a difference, however, between occasional forgetfulness and behavior that may be cause for concern. Not recognizing a familiar face, trouble performing common tasks (like using the telephone or driving home), or being unable to recall recent information are red flags that need to be checked by a doctor.

Who Gets AD?

Also known as late-onset Alzheimer’s disease, AD is primarily a disease of older adults. The first noticeable symptoms can occur as early as age 60.AD sometimes can affect people as young as 30. This type of AD is called early-onset AD. It’s rare and affects less than one out of every 1,000 people with AD. When AD runs in families, it’s called familial Alzheimer’s disease (FAD). 

The underlying causes and specific risk factors for AD remain unclear. Yet experts believe AD is likely due to a combination of environmental and genetic factors. Lifestyle choices such as diet, exercise, and staying mentally active are also factors. 

About 5.2 million Americans have AD, according to the Alzheimer’s Association of America. That number will only climb as the elderly population rises.

According to the same source, AD is the sixth leading cause of death in the United States and the fifth leading in Americans age 65 and older.

What’s Being Done?

Scientists are working to better understand AD. The goal is to create more effective early diagnostic tools, improve treatments, and perhaps even discover a cure. 

Currently there are numerous resources and services for people who suffer with AD and their loved ones and caregivers. Some current treatment options even may slow the progression of AD, but their effectiveness varies and diminishes over time.

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Show Sources

  • Albert, M. S., Dekosky, S. T., Dickson, D., Dubois, B., Feldman, H. H., Fox, N. C., et al. (2011). The diagnosis of mild cognitive impairment due to Alzheimer's disease: Recommendations from the National Institute on Aging and Alzheimer's Association workgroup. Alzheimers Dement.
  • Alzheimer's Association. (2011). Press Release: New Criteria and Guidelines for the Diagnosis of Alzheimer's Disease Published for the first Time in 27 Years. The Alzheimer's Association, 1-11.
  • Arvanitakis, Z., Wilson, R. S., Bienias, J. L., Evans, D. A., & Bennett, D. A. (2004). Diabetes mellitus and risk of Alzheimer disease and decline in cognitive function. Arch Neurol, 61(5), 661-666.
  • Ballard, C., Gauthier, S., Corbett, A., Brayne, C., Aarsland, D., & Jones, E. (2011). Alzheimer's disease. Lancet, 377(9770), 1019-1031.
  • Bird, T. D. (2010). Early-Onset Familial Alzheimer Disease. University of Washington, Gene Review.
  • Birks, J., & Grimley Evans, J. (2009). Ginkgo biloba for cognitive impairment and dementia. Cochrane Database Syst Rev(1), CD003120.
  • Bosco, D., Fava, A., Plastino, M., Montalcini, T., & Pujia, A. (2011). Possible implications of Insulin Resistance and Glucose metabolism in Alzheimer's disease pathogenesis. J Cell Mol Med.
  • Boyle, P. A., Buchman, A. S., Barnes, L. L., & Bennett, D. A. (2010). Effect of a purpose in life on risk of incident Alzheimer disease and mild cognitive impairment in community-dwelling older persons. Arch Gen Psychiatry, 67(3), 304-310.
  • Boyle, P. A., Buchman, A. S., Barnes, L. L., James, B. D., & Bennett, D. A. (2010). Association between life space and risk of mortality in advanced age. J Am Geriatr Soc, 58(10), 1925-1930.
  • Brinkley, T. E., Lovato, J. F., Arnold, A. M., Furberg, C. D., Kuller, L. H., Burke, G. L., et al. (2010). Effect of Ginkgo biloba on blood pressure and incidence of hypertension in elderly men and women. Am J Hypertens, 23(5), 528-533.
  • Daviglus, M. L., Bell, C. C., Berrettini, W., Bowen, P. E., Connolly, E. S., Cox, N. J., et al. (2010). NIH State-of-the-Science Conference Statement: Preventing Alzheimer's Disease and Cognitive Decline. NIH Consens State Sci Statements, 27(4).
  • De Felice, F. G., Vieira, M. N., Bomfim, T. R., Decker, H., Velasco, P. T., Lambert, M. P., et al. (2009). Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers. Proc Natl Acad Sci U S A, 106(6), 1971-1976.
  • deIpolyi, A. R., Rankin, K. P., Mucke, L., Miller, B. L., & Gorno-Tempini, M. L. (2007). Spatial cognition and the human navigation network in AD and MCI. Neurology, 69(10), 986-997.
  • DeKosky, S. T., Williamson, J. D., Fitzpatrick, A. L., Kronmal, R. A., Ives, D. G., Saxton, J. A., et al. (2008). Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA, 300(19), 2253-2262.
  • Fillit, H. M., Butler, R. N., O'Connell, A. W., Albert, M. S., Birren, J. E., Cotman, C. W., et al. (2002). Achieving and maintaining cognitive vitality with aging. Mayo Clin Proc, 77(7), 681-696.
  • Harold, D., Abraham, R., Hollingworth, P., Sims, R., Gerrish, A., Hamshere, M. L., et al. (2009). Genome-wide association study identifies variants at CLU and PICALM associated with Alzheimer's disease. Nat Genet, 41(10), 1088-1093.
  • Herrmann, W., & Obeid, R. (2011). Homocysteine: a biomarker in neurodegenerative diseases. Clin Chem Lab Med, 49(3), 435-441.
  • Keating, D. J., Chen, C., & Pritchard, M. A. (2006). Alzheimer's disease and endocytic dysfunction: clues from the Down syndrome-related proteins, DSCR1 and ITSN1. Ageing Res Rev, 5(4), 388-401.
  • Ladika, D. J., & Gurevitz, S. L. (2011). Identifying the most common causes of reversible dementias: a review. JAAPA, 24(3), 28-31, 57.
  • Li, K., Dai, D., Zhao, B., Yao, L., Yao, S., Wang, B., et al. (2010). Association between the RAGE G82S polymorphism and Alzheimer's disease. J Neural Transm, 117(1), 97-104.
  • McKhanna, G. M., Knopmanc, D. S., Chertkowd, H., Hyman, B. T., Clifford R. Jack, J., Kawash, C. H., et al. (2011). The diagnosis of dementia due to Alzheimer’s disease: Recommendations from the National Institute on Aging and the Alzheimer’s Association workgroup. Alzheimer’s & Dementia, 1–7.
  • Nation, D. A., Hong, S., Jak, A. J., Delano-Wood, L., Mills, P. J., Bondi, M. W., et al. (2011). Stress, exercise, and Alzheimer's disease: A neurovascular pathway. Med Hypotheses.
  • National Library of Medicine. (2011). Alzheimer's Disease. Medline Plus; U.S. National Library of Medicine; National Institutes of Health.
  • NCCAM. (2011). National Center for Complementary and Alternative Medicine: The Ginkgo Evaluation of Memory (GEM) Study. National Institutes of Health' National Center for Complementary and Alternative Medicine.
  • NIA. (2008). Alzheimer's Disease:  Unraveling the Mystery. National Institute on Aging; National Institutes of Heath; US Department of Health and Human Services; NIH Publication Number 08-3782, 1-43.
  • NIA. (2011). Caring for a Person with Alzheimer's Disease; Medicine Chart. National Institutes of Health; National Institute on Aging; Alzheimer's Disease Education & Referral Center.
  • NINDS. (2010). NINDS Alzheimer's Disease Information Page. National Institute of Neurological Disorders and Stroke; National Institutes of Health; US Department of Health & Human Services.
  • NINDS. (2011). Dementia: Hope Through Research. National Institute of Neurological Disorders and Stroke of the National Institutes of Health.
  • Panza, F., Frisardi, V., Imbimbo, B. P., D'Onofrio, G., Pietrarossa, G., Seripa, D., et al. (2010). Bapineuzumab: anti-beta-amyloid monoclonal antibodies for the treatment of Alzheimer's disease. Immunotherapy, 2(6), 767-782.
  • Redish, A. D. (2001). The hippocampal debate: are we asking the right questions? Behav Brain Res, 127(1-2), 81-98.
  • Reitz, C., Brayne, C., & Mayeux, R. (2011). Epidemiology of Alzheimer disease. Nat Rev Neurol, 7(3), 137-152.
  • Reitz, C., den Heijer, T., van Duijn, C., Hofman, A., & Breteler, M. M. (2007). Relation between smoking and risk of dementia and Alzheimer disease: the Rotterdam Study. Neurology, 69(10), 998-1005.
  • Seneff, S., Wainwright, G., & Mascitelli, L. (2011). Nutrition and Alzheimer's disease: The detrimental role of a high carbohydrate diet. Eur J Intern Med, 22(2), 134-140.
  • Snitz, B. E., O'Meara, E. S., Carlson, M. C., Arnold, A. M., Ives, D. G., Rapp, S. R., et al. (2009). Ginkgo biloba for preventing cognitive decline in older adults: a randomized trial. JAMA, 302(24), 2663-2670.
  • Solomon, P. R., Adams, F., Silver, A., Zimmer, J., & DeVeaux, R. (2002). Ginkgo for memory enhancement: a randomized controlled trial. JAMA, 288(7), 835-840.
  • Traykov, L., Rigaud, A. S., Cesaro, P., & Boller, F. (2007). [Neuropsychological impairment in the early Alzheimer's disease]. Encephale, 33(3 Pt 1), 310-316.
  • Uc, E. Y., Rizzo, M., Anderson, S. W., Shi, Q., & Dawson, J. D. (2004). Driver route-following and safety errors in early Alzheimer disease. Neurology, 63(5), 832-837.
  • Wegiel, J., Gong, C. X., & Hwang, Y. W. (2011). The role of DYRK1A in neurodegenerative diseases. FEBS J, 278(2), 236-245.
  • Wilson, R. S., Mendes De Leon, C. F., Barnes, L. L., Schneider, J. A., Bienias, J. L., Evans, D. A., et al. (2002). Participation in cognitively stimulating activities and risk of incident Alzheimer disease. JAMA, 287(6), 742-748.
  • Yu, F. (2011). Guiding Research and Practice: A Conceptual Model for Aerobic Exercise Training in Alzheimer's Disease. Am J Alzheimers Dis Other Demen.

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