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Alzheimer's disease (AD) is a progressive neurocognitive disease that slowly erodes an individual's memory, judgment, cognition, learning, and, eventually, ability to function. It is the leading cause of dementia in the elderly. Alzheimer's disease can affects a person's mood, thinking, and behavior, as well as their overall personality, disposition, and sense of self.

The condition is characterized by language deterioration, impaired ability to mentally manipulate visual information, poor judgment, confusion, and restlessness. It is most commonly found in adults over age 60, but it can at times occur in younger adults as well. It is not considered a normal process of aging. According to 2021 figures published in the journal Alzheimer's & Dementia, it is estimated to occur in 5 percent of individuals between the ages of 65 and 75. One's risk of developing the disease tends to increase with age: Nearly 14 percent of those between ages 75 and 84 may develop Alzheimer's; for adults 85 years or older, prevalence approaches 35 percent.

Early signs of the condition may include forgetting important dates or events, misplacing things, finding it hard to complete familiar tasks at home or work, being confused about time or place, becoming easily lost in places one knows well, developing problems using words, losing planning or problem-solving abilities, and showing mood or personality changes. Because some of these symptoms may occur as part of normal aging, they sometimes go unrecognized or undiagnosed for a significant period of time. As the condition progresses, its symptoms tend to become more noticeable and disruptive.


Common symptoms of Alzheimer’s disease include:

  • Forgetting appointments or events
  • Feeling confused or overwhelmed by routine tasks, like paying bills or going grocery shopping
  • Difficulty performing basic hygiene or self-care tasks, such as getting dressed or taking a shower
  • Poor short-term memory for conversations; repeating statements, stories, or questions over and over
  • Routinely losing possessions; may put them in strange locations without realizing
  • Struggling to express thoughts or ideas; may forget frequently used words or names for objects
  • Forgetting names of loved ones, especially in the later stages of the disease
  • Poor judgment—for example, ventures outdoors in bad weather without adequate clothing
  • Inappropriate social behavior
  • Sudden personality changes, such as uncharacteristic anger
  • Depression, apathy or social withdrawal
  • An increasing tendency to be distrustful or paranoid
  • Hallucinations or delusions, particularly in the later stages of the disease

According to the DSM-5, Alzheimer's disease can be classified as either a major or mild neurocognitive disorder, based on the severity of cognitive decline that is observed. It is typically diagnosed based on symptoms, family history, or following genetic testing to determine a causative genetic mutation. Though genetic testing is not always conducted, if a mutation is found to be present and/or there is a known family history of Alzheimer’s, the diagnosis is deemed “probable”; if not, the diagnosis is considered “possible.” Alzheimer’s can only be definitively diagnosed after death when the brain is examined for plaques and other visible markers of the disease; however, many doctors feel comfortable offering a probable diagnosis based on symptoms and family history.

To qualify as a major neurocognitive disorder, there must be:

  • Clear evidence of a decline in memory and learning
  • A steady progression of symptoms
  • A gradual decline in cognition
  • An inability to live independently
  • The absence of other neurodegenerative, cerebrovascular, or neurological or mental diseases

To qualify as a mild neurocognitive disorder, there may or may not be evidence of genetic mutation from family history or testing, but the following symptoms should be present:

  • Clear evidence of a decline in memory and learning
  • A steady progression of symptoms
  • A gradual decline in cognition
  • The absence of other neurodegenerative, cerebrovascular, or neurological or mental diseases

The deficits must cause significant impairment in social or occupational functioning and represent a notable decline from a previous level of functioning.

Mild stages of Alzheimer's may include depression and/or apathy. With moderately severe Alzheimer's, psychotic features such as hallucinations or delusions, irritability, agitation, combativeness, and wandering behaviors may be observed. With severe Alzheimer's, gait disturbance, incontinence, seizures, difficulty swallowing, and sudden muscle contractions may occur.

How is Alzheimer’s disease different from dementia?

Alzheimer’s disease is one possible cause of dementia, a broad category of related symptoms that include memory loss, language challenges, mood changes, and a general loss of functioning. While Alzheimer’s is not the only cause of dementia, it is the most common; nearly 70 percent of those with dementia are thought to have AD. Other causes of dementia include vascular disease, Parkinson’s disease, and HIV.

Are people with Alzheimer’s disease aware that they have it?

It is common in the early stages of Alzheimer’s for the person with the disease to be aware that something is wrong. They may recognize that they are having difficulty remembering things or getting lost frequently, and may become frustrated or agitated as a result. Many people who are formally diagnosed with Alzheimer’s are cognizant of their diagnosis and may be able to take steps to prepare themselves and their loved ones for their future decline. As the disease progresses, many people with Alzheimer’s often seem to become less aware of their symptoms, though they may still express frustration or seem to feel that something is wrong. They may also become depressed as a result of this continual frustration and ongoing sense of decline.

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Age is the strongest risk factor for Alzheimer's, although the condition is not a typical or normal aspect of aging.

Genetic susceptibility to Alzheimer's is another important variable. Those who have a parent or sibling with Alzheimer’s are more likely to develop it themselves. Genetic variants (alleles) such as apolipoprotein E4 (APOE), Amyloid precursor protein (APP), Presenilin-1 (PS-1), and Presenilin-2 (PS-2) can increase an individual's chance of developing Alzheimer's. These proteins can cause or exacerbate both structural and chemical problems in the brain, disconnecting areas of the brain that normally work together.

In addition to age and family history, risk factors for AD may include longstanding high blood pressure, head trauma, and neuronal injury. Medical conditions such as heart disease, diabetes, stroke, high blood pressure, and high cholesterol can damage the heart and blood vessels, which raises the risk. Because women usually live longer than men, they are more likely to develop Alzheimer's.

Is Alzheimer’s disease genetic?

The genetic roots of Alzheimer’s are not yet fully understood. However, individuals who have a parent or sibling with the disease do appear to be at higher risk, suggesting that genetics do play a significant role. In addition, certain genes and genetic variants appear to confer additional risk, such as the e4 variant of the APOE gene.

How does the APOE gene play a role in Alzheimer’s disease?

Several specific genes have been implicated in Alzheimer’s disease, including apolipoprotein E gene (APOE), which is involved in making a protein that helps move cholesterol and other fats through the bloodstream. APOE is located on chromosome 19, and each person carries two copies of it (one inherited from each parent). There are currently three known variants of the APOE gene: e2, e3, and e4. The most common variant, e3, is not thought to increase or decrease the risk of Alzheimer’s. The e2 variant is relatively rare but appears to offer some protection against the disease. The e4 variant (one copy of which is carried by approximately a quarter of the population) is associated with a heightened risk of Alzheimer's in certain populations; having two copies of the variant confers even greater risk, but occurs in only 2 to 3 percent of people. 


The progression of Alzheimer's disease cannot be slowed down, as the disease cannot be cured and impaired functions may not be restored. However, symptoms can be targeted to improve the quality of a person's life and reduce the impact of the more troubling aspects of the illness.

Cholinesterase inhibitors are a class of drugs prescribed to treat symptoms related to memory, thinking, language, judgment, and other thought processes. Three cholinesterase inhibitors commonly prescribed include Donepezil (Aricept) approved to treat all stages of Alzheimer's; Rivastigmine (Exelon) approved to treat mild to moderate Alzheimer's; and Galantamine (Razadyne) approved to treat mild to moderate Alzheimer's. A second type of medication, memantine (Namenda), is approved by the FDA for the treatment of moderate to severe Alzheimer’s. Memantine is prescribed to improve memory, attention, reason, language, and the ability to perform simple tasks. It can be used alone or with other Alzheimer’s disease treatments. In mid-2021, the FDA approved another Alzheimer's drug, aducanumab; however, this approval was widely criticized and evidence of the drug's efficacy is contested.

Treatment may also focus on managing a patient's behavioral problems, confusion, and agitation; modifying the home environment; and supporting the family. Underlying disorders that contribute to confusion should also be identified and treated. Behavior modification may be helpful for some patients in controlling unacceptable or dangerous activity.

Can Alzheimer’s disease be cured?

Currently, there are no treatments that can cure Alzheimer’s disease or meaningfully slow its progression. Existing treatments may, however, improve quality of life and may help alleviate some symptoms of the disease.

How much care is needed during the different stages of Alzheimer’s?

Alzheimer’s disease does not follow an exact timeline, and individuals may lose independence at different rates. In the early stage of Alzheimer’s, many people with the disease are still able to carry out many basic tasks, such as eating and bathing, on their own, and may only need assistance with certain activities, such as paying bills or driving. As the disease progresses, however, more intensive care will likely be needed. 

National Institute of Mental Health
National Institute of Aging (2006). Alzheimers Disease Fact Sheet
National Institute of Aging (2007). Understanding Stages and Symptoms of Alzheimer's Disease
2021 Alzheimer's Disease Facts and Figures. (2021). Alzheimer's & Dementia, 17(3), 327–406.
National Institute of Neurological Disorders and Stroke
National Institutes of Health - National Library of Medicine  
Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition
Last updated: 10/22/2021