What Is Alzheimer’s Disease?

The most common type of dementia

Alzheimer’s disease is a brain disorder that slowly impacts a person’s ability to think and remember. It worsens over time until it severely affects how those with the disease function and interact with the world. Alzheimer’s is rare before age 65, but past this age, the risk doubles about every five years. However, many people live into their 90s and beyond without developing Alzheimer’s. 

Read more to learn about Alzheimer’s symptoms, causes, diagnosis, treatment, and related topics. 

Closeup shot of young person holding senior wrinkled hand

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Alzheimer’s vs. Dementia

The terms Alzheimer's and dementia are often used interchangeably, but they are different. Dementia is an umbrella term that describes a person's inability to think, remember, and make decisions, impacting their ability to perform basic daily tasks. Although dementia typically affects older adults, it is not a normal part of aging.

Alzheimer's disease is the most common form, affecting around 60–80% of people with dementia. People with Alzheimer's tend to forget new information quickly and have trouble recalling that information, even with clues from loved ones.

Early-Onset vs. Late-Onset Alzheimer’s

Most people with Alzheimer's have late-onset disease, affecting people 65 and older. However, about 5% of those with Alzheimer's have early-onset, which can strike people in their 40s and 50s.

Early-onset Alzheimer's is typically more severe than late-onset, and it may take longer to be diagnosed. Symptoms may be less about memory and include issues such as:

  • Attention or planning challenges
  • Speech difficulty
  • Vision changes

This article focuses on late-onset Alzheimer's unless otherwise specified.


Alzheimer’s symptoms vary depending on the severity of the disease. Unlike other kinds of brain problems, symptoms of Alzheimer’s come on gradually. Memory challenges are characteristic of Alzheimer’s, but visual processing or language issues can also occur.

Early-Stage Alzheimer’s

People with early-stage Alzheimer's might not have symptoms that are obvious to everyone, but those with whom they are close might notice difficulties with:

  • Forgetting important appointments
  • Mixing up events and people
  • Misplacing things often
  • Taking care of bills
  • Carrying out familiar tasks

Talk to a healthcare provider if you or a loved one shows signs of Alzheimer's. They can determine whether the symptoms are due to mild cognitive impairment, which is a part of normal aging, or dementia. Looking back, you may find it evident that your loved one was showing early symptoms of Alzheimer's. But because the disease comes on slowly, identifying it can prove challenging.

Moderate Alzheimer’s

In moderate disease, symptoms become more apparent. For example, an individual might become confused about the year or where they are and how they got there. They might not remember basic information about themselves and their family members. Some people also experience personality changes, agitation or depression, or delusions.

Severe Alzheimer’s

In the later stages, individuals become severely impaired in memory and cognition. They may lose the ability to communicate clearly and respond to their environment and have difficulty controlling movement. These individuals need round-the-clock monitoring and care.


People with Alzheimer’s typically live four to eight years after diagnosis, but this can vary. The disease may progress slowly in some people but more quickly in others, partly depending on their response to therapy and other medical conditions.


People with Alzheimer’s can suffer complications of their disease. Certain common problems among older adults may worsen due to communication challenges. Some examples are:

What Causes Alzheimer’s Disease?

The exact cause of Alzheimer's is unknown. However, researchers do know it has to do with changes in the brain. One theory is that abnormal strands and clumps of specific peptides in the brain may trigger inflammation. However, it is likely that many factors, not just one, cause the disease.

Risk Factors

Increasing age is the most critical risk factor for Alzheimer's. Other risk factors for Alzheimer's are less clear. Some other factors that may contribute to risk include:

Is Alzheimer’s Genetic?

Genes and environment play a role in Alzheimer's risk. For example, if you have a parent or sibling with Alzheimer's, you might have double the chance of getting it compared to someone who doesn't have a family history of the disease.

The most significant gene for increasing the risk of Alzheimer's is apolipoprotein E (APOE). People with Alzheimer's have a specific variation of this gene about two to three times more often than people without the disease. However, many people with this gene variant never get Alzheimer's. 

One exception is early-onset Alzheimer's. The subset of people with this less common form of Alzheimer's have versions of genes that almost always lead to Alzheimer's if inherited from a parent.

Down Syndrome and Alzheimer's Risk

About 70% of people with Down syndrome develop Alzheimer’s by age 60. This may be because they have an extra copy of the genes on the 21st chromosome. One of these, the amyloid precursor protein gene, plays an important role in Alzheimer’s. Having an extra copy seems to increase one’s risk.  

Confirming an Alzheimer’s Diagnosis

Although researchers are working on it, there is no singular test for diagnosing Alzheimer's. A healthcare provider will take one or more of the following to diagnose someone with Alzheimer's:

  • Medical history: A healthcare provider will discuss the evolution of symptoms with the individual experiencing them and someone close to them.
  • Cognitive tests: Healthcare providers use various cognitive tests to assess the degree and characteristics of a person's impairment.
  • Blood tests: These tests help providers identify potentially treatable medical issues that might be mistaken for Alzheimer's disease or conditions that might worsen symptoms. (For example, a test for thyroid stimulating hormone might help rule out hypothyroidism as an underlying cause, or a complete blood count might help rule out an infection.)
  • Imaging techniques: Healthcare providers use imaging techniques, such as an MRI, CT, or SPECT scan, to help diagnose Alzheimer's and distinguish it from related conditions.

More recently, some clinicians have started testing the cerebral spinal fluid, which cushions your brain and spinal cord, for specific markers of Alzheimer's disease. However, they rarely perform these tests, which are usually the responsibility of specialists.

Alzheimer’s Treatment

Treating Alzheimer’s requires a team of experts using different treatment methods to help reduce symptoms, slow decline, and maximize quality of life.

Non-Pharmacological Interventions

Memory aids can be helpful in the early stages. Maintaining consistent but straightforward routines can help people with Alzheimer's navigate their environment. Healthcare providers may help the caregiver find better ways to communicate with the affected person and reduce problematic behaviors.

It's also critical to managing other medical conditions. For example, a person with Alzheimer's may need to stop taking medications that make it more challenging to think clearly. Or they may have a medical problem worsening their symptoms, like a urinary tract infection or an underlying vitamin B12 deficiency.


The FDA approved three medications in a drug class called cholinesterase inhibitors to treat Alzheimer's. These medications include:

  • Aricept (donepezil)
  • Razadyne (galantamine)
  • Exelon (rivastigmine)

One additional FDA-approved medication is called Namenda (memantine). A healthcare provider may prescribe one of the four approved medications alone or combine a cholinesterase inhibitor with Namenda.

In some people, these drugs may reduce symptoms or slow symptom progression. However, they don't treat the underlying problems that lead to Alzheimer's.

New and Emerging Treatments

In 2021, the FDA approved Aduhelm (aducanumab), a costly biologic-type therapy, to treat Alzheimer’s. Unlike previous treatments, it potentially targets the underlying cause of the disease. However, it has been controversial because some experts aren’t sure whether its potential risks of brain swelling and bleeding outweigh its unclear benefits.  

In January 2023, the FDA approved another biologic with a similar mode of action, Leqembi (lecanemab-irmb). It’s currently approved for people with mild disease, and like Aduhelm, it’s somewhat controversial. 

Emerging treatments are currently undergoing clinical trials. Some therapies target the abnormal peptide clumps, and others work on inflammation or blood vessels. If one or more of these new therapies proves effective over the long term, it may soon expand treatment options.  

Living With Alzheimer’s Disease

People with Alzheimer’s need social, emotional, physical, and medical support to enhance their quality of life. These needs change as a person progresses from mild to moderate to severe disease. 

Support for Family and Caregivers

Family members and caregivers of people with Alzheimer’s provide the most important cornerstone of their treatment. However, caregiving burnout is a hazard, particularly for individuals who don’t have enough support. Prioritize your health and needs so you can continue supporting your loved one. 

Alzheimer’s Organizations

Various organizations work to raise money for research, education, and support for people with Alzheimer’s and their families. Some are the Alzheimer’s Association, the Alzheimer’s Foundation of America, and Alzheimer’s Disease International. 

The Alzheimer’s Association provides a 24-hour hotline to help connect people living with Alzheimer's and their caregivers to local resources: 800-272-3900.

When Is Alzheimer’s Awareness Month?

In June, the Alzheimer’s Association highlights Alzheimer’s and Brain Awareness Month. Many people choose to contribute to the cause by hosting a fundraiser for Alzheimer’s research on the summer solstice. 

In November, the Alzheimer’s Foundation of America also emphasizes Alzheimer’s Awareness Month. Many people wear teal or light up buildings in this color to help raise awareness for the disease.  


Alzheimer's is a chronic progressive brain disorder and the most common form of dementia. It causes symptoms like memory loss and impaired attention, progressing from mild to severe, so the person can no longer handle their daily activities without help. Talk to a healthcare provider if you or a loved one suspects Alzheimer's. A provider can offer testing, diagnosis, and treatment options. People with Alzheimer's and their caregivers benefit from solid support systems.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Ruth Jessen Hickman, MD
Ruth Jessen Hickman, MD, is a freelance medical and health writer and published book author.