Alzheimer's disease

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Alzheimer's disease
Alzheimers disease - MRI.jpg

Post-autopsy brain scans: A brain with Alzheimer's disease (left) as compared to a normal brain (right)
ICD-10 ICD10 F84.0-F84.1, ICD10 F84.0-F84.1
ICD-9 331.0


OMIM 104300
MedlinePlus 000760

Alzheimer's disease is also known as Alzheimer disease, Alzheimer's and simply AD.

Alzheimer's is the most common cause of dementia, afflicting at least 24 million people worldwide. Alzheimer's is a terminal disease for which there is currently no known cure. It is most commonly found in people over 65 years old, although a less-common form called Familial Alzheimer's disease, or "early-onset Alzheimer's", also occurs, affecting about 1%—5% of the total of Alzheimer's sufferers.[1]

Typically, the disease begins many years before it is diagnosed. In its early stages, short-term memory loss is the most common symptom, which is often initially thought by the sufferer to be caused by other factors, such as aging or stress.[2] Later symptoms of the disease include confusion, anger, mood swings, language breakdown, long-term memory loss, and the general "withdrawal" of the sufferer as his or her senses decline.[2][3] Gradually the sufferer will lose minor, and then major bodily functions, until death finally occurs.[4] Survival after diagnosis has been estimated to be between 5 and 20 years.[5][6]


A classification has been proposed by the the ad hoc International Working Group for New Research Criteria for the Diagnosis of AD.[7]

Asymptomatic at-risk for Alzheimer's disease

Asymptomatic at-risk for Alzheimer's disease includes asymptomatic patients with a positive biomarker. Biomarkers include apolipoprotein E4.

Presymptomatic Alzheimer's disease

Presymptomatic Alzheimer's disease includes people with autosomal dominant mutation known to have full penetrance

Prodromal Alzheimer's disease

Prodromal Alzheimer's disease includes patients with positive biomarkers who have mild cognitive dysfunction that does not cause significant functional impairment.

Alzheimer's Dementia

Alzheimer's dementia indicates functional impairment meeting criteria for dementia.


Common symptoms of dementia include:

   A decline in memory
   Changes in thinking skills
   Poor judgment and reasoning
   Decreased focus and attention
   Decreased language ability
   Negative changes in behavior

Although the symptoms are common, they are typically experienced in unique ways.[8] "Stages" are commonly referred to by professionals to describe the progressive nature of Alzheimer's (typically "early", "mid" and "late onset") but the symptoms can cross over these "boundaries" for many sufferers.


The symptoms of Alzheimer's disease are generally reported to a doctor or physician when memory-loss (or symptoms surrounding memory loss) begin to pose a serious concern. When Alzheimer's disease is suspected, diagnosis is typically confirmed by a behavioural assessment, and some form of cognitive test. Often this is followed by a brain scan.[9]

Laboratory tests

Apolipoprotein E4

Although apolipoprotein E4 is an important susceptibility gene for Alzheimer's disease][10], its sensitivity and specificity are insufficient (65 and 68 percent, respectively) to be used as a diagnostic test.[11]

However, the level of apolipoprotein E4 in cerebrospinal fluid may be predictive.[12]

Amyloid-beta protein

Amyloid-beta protein may be elevated in the cerebrospinal fluid of some patients.[12]


The etiology of Alzheimer's disease is incompletely understood. Alzheimer's disease is associated with senile plaques and neurofibrillary tangles in the brain.[13] The incorrect folding of proteins leads to the formation of amyloid plaques. The prion protein (PrPC) may be the cellular receptor for amyloid-beta oligomer.[14] Current research aims to determine if such plaques are the result of, or the cause of, Alzheimer's disease.

Regarding biomarkers, one study found that "a reduction in the CSF Aβ42 level denotes a pathophysiological process that significantly departs from normality (ie, becomes dynamic) early, whereas the CSF total tau level and the adjusted hippocampal volume are biomarkers of downstream pathophysiological processes". [15]

Although there is a genetic susceptibility in a small percentage of people, Alzheimer's is not considered a genetic illness. The greatest risk factor for developing Alzheimer's is age, as the percentage of people developing it dramatically increases after age 65 and beyond. Major environmental/lifestyle risk factors include a diet high in saturated fats that are typical of the standard western diet, smoking, and long-term exposure to environmental toxins such as aluminum. Research is ongoing.


No treatment has been found to stop or reverse the disease. Many preventive measures have been suggested for Alzheimer's disease, but their values are uncertain: mental stimulation, exercise, and a Mediterranean style diet are usually recommended, both as possible prevention and as a sensible way of managing the disease.[16]


As of 2023, available medications offer relatively small symptomatic benefit for some patients but generally do not slow disease progression. Newer monoclonal antibody treatments against beta-amyloid protein, for example, the drug Leqembi, have been approved in the United States, but they only slightly reduce the rate of disease progression and have significant side effects, including brain bleeding and in rare cases, death. These drugs cost over $20,000 a year, which could be prohibitively expensive for many patients.

Randomized controlled trials showed either small or absent benefit from acetylcholinesterase inhibitors[17] such as donepezil.[18][19][20]

The N-methyl-d-aspartate receptor antagonist memantine has shown some effectiveness[21] but does not add benefit to donepezil .[20]

Care management

Due to the incurable and degenerative nature of the disease care-management of Alzheimer's is essential. The role of the main caregiver is often taken by the spouse or a close relative.[22] Caregivers may themselves suffer from stress, over-work, depression, and from being physically assailed.[23]

Alzheimer's in society

Famous people who have, or have died of Alzheimer's disease, are the US president Ronald Reagan, the UK Prime minister Harold Wilson, the writers Terry Pratchett and Iris Murdoch, and the film stars Rita Hayworth and Charlton Heston.


Auguste D, first recorded patient with the newly recognised form of dementia.

Alzheimer’s disease is named after Dr. Alois Alzheimer, the German physician who first described it. In 1901, Alzheimer observed a 51-year-old patient at the Frankfurt asylum named Auguste Deter. Her symptoms included memory loss, language problems, and unpredictable behavior. In 1906, she died and Dr. Alzheimer noticed unusual pathology in her brain tissue; he found many abnormal clumps (now called amyloid plaques) and tangled bundles of fibers (now called neurofibrillary, or tau, tangles).


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