Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease that usually starts slowly and progressively worsens.[2] It is the cause of 60–70% of cases of dementia.[2] The most common early symptom is difficulty in remembering recent events.[1] As the disease advances, symptoms can include problems with language, disorientation (including easily getting lost), mood swings, loss of motivation, self-neglect, and behavioral issues.[1][2] As a person's condition declines, they often withdraw from family and society.[1] Gradually, bodily functions are lost, ultimately leading to death.[11] Although the speed of progression can vary, the typical life expectancy following diagnosis is three to nine years.[8][12]

Alzheimer's disease
Drawing comparing a normal aged brain (left) and the brain of a person with Alzheimer's (right). Characteristics that separate the two are pointed out.
  • ˈaltshʌɪməz
SymptomsDifficulty in remembering recent events, problems with language, disorientation, mood swings[1][2]
ComplicationsDehydration and Pneumonia in the terminal stage[3]
Usual onsetOver 65 years old[4]
DurationLong term[2]
CausesPoorly understood[1]
Risk factorsGenetics, head injuries, depression, hypertension[1][5]
Diagnostic methodBased on symptoms and cognitive testing after ruling out other possible causes[6]
Differential diagnosisNormal aging[1]
MedicationAcetylcholinesterase inhibitors, NMDA receptor antagonists (small benefit),[7]
PrognosisLife expectancy 3–9 years[8]
Frequency29.8 million (2015)[9]
DeathsFor all dementias 1.9 million (2015)[10]

The cause of Alzheimer's disease is poorly understood.[1] There are many environmental and genetic risk factors associated with its development. The strongest genetic risk factor is from an allele of APOE.[13][14] Other risk factors include a history of head injury, clinical depression, and high blood pressure.[1] The disease process is largely associated with amyloid plaques, neurofibrillary tangles, and loss of neuronal connections in the brain.[11] A probable diagnosis is based on the history of the illness and cognitive testing with medical imaging and blood tests to rule out other possible causes.[6] Initial symptoms are often mistaken for normal aging.[1] Examination of brain tissue is needed for a definite diagnosis, but this can only take place after death.[11] Good nutrition, physical activity, and engaging socially are known to be of benefit generally in aging, and these may help in reducing the risk of cognitive decline and Alzheimer's; in 2019 clinical trials were underway to look at these possibilities.[11] There are no medications or supplements that have been shown to decrease risk.[15]

No treatments stop or reverse its progression, though some may temporarily improve symptoms.[2] Affected people increasingly rely on others for assistance, often placing a burden on the caregiver.[16] The pressures can include social, psychological, physical, and economic elements.[16] Exercise programs may be beneficial with respect to activities of daily living and can potentially improve outcomes.[17] Behavioral problems or psychosis due to dementia are often treated with antipsychotics, but this is not usually recommended, as there is little benefit and an increased risk of early death.[18][19]

As of 2015, there were approximately 29.8 million people worldwide with AD[9] with about 50 million of all forms of dementia as of 2020.[2] It most often begins in people over 65 years of age, although up to 10 per cent of cases are early-onset affecting those in their 30's to mid 60's.[11][4] Women get sick more often than men.[20] It affects about 6% of people 65 years and older.[1] In 2015, all forms of dementia resulted in about 1.9 million deaths.[10] The disease is named after German psychiatrist and pathologist Alois Alzheimer, who first described it in 1906.[21] Alzheimer's financial burden on society is large, on par with the costs of cancer and heart disease, with a 2013 study estimating an annual cost of $200 billion (equivalent to $222 billion in 2020) in the US alone.[15][22]