What Is Alzheimer’s Disease?

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Alzheimer’s disease is a progressive and irreversible brain condition. The two most common symptoms of the condition are confusion and memory loss. Alzheimer's disease slowly causes thinking and memory to deteriorate to the point that even simple tasks become difficult or impossible.

Alzheimer’s disease can eventually cause a person to lose their ability to respond to their environment, including becoming unable to carry out a conversation.

It is also the most common cause of dementia in older adults. The Alzheimer's Association suggests that somewhere between 60% and 80% of dementia is caused by Alzheimer's disease.

According to the Centers for Disease Control and Prevention (CDC), Alzheimer's disease is the fifth leading cause of death for adults over the age of 65.

While there is no cure for Alzheimer's , there are treatments available that can help slow the disease's progression. Behavioral and medication treatments can also help people cope with the symptoms of the disease.


The most common symptom that people begin to notice is difficulty remembering new information. This symptom may be subtle at first, and people may initially dismiss it as normal forgetting or normal age-related memory decline.

Because of the progressive nature of Alzheimer's disease, this forgetting will eventually become more pronounced. People may also begin to exhibit more severe memory problems as well as other symptoms including:

  • Behavioral and personality changes
  • Confusion
  • Difficulty speaking
  • Difficulty with multi-step tasks
  • Disorientation
  • Mood changes
  • Problems remembering events, time, and places
  • Unfounded suspicions
  • Repeating questions
  • Sleeping difficulties
  • Swallowing problems
  • Trouble recognizing family and friends
  • Trouble walking
  • Wandering or getting lost


While symptoms can vary from person to person, the progression of the disease usually follows a pattern that can be broken down into three general stages.

Early Stage

During this early stage of the disease, people begin to experience mild symptoms but often still function and live independently. While they continue to live their lives, including doing things like socializing and working, they may have memory lapses that make it difficult to remember words, names, and the locations of everyday things.

Some symptoms that a person might experience at this point include:

  • Difficulty with organizing and planning
  • Difficulty remembering appointments
  • Forgetting the sequence of steps needed to complete a task
  • Forgetting recent conversations or recently learned information
  • Losing or misplacing things
  • Trouble remembering the right word to describe something
  • Trouble judging how much time is needed to finish a task

Middle Stage

This stage of the disease is usually the longest. During this time, symptoms grow progressively worse. Memories, including long-term memories , begin to decline.

Behavioral and emotional changes are also common. People may experience frustration, anxiety, and agitation. It becomes increasingly difficult for people to function and they become dependent on others to help with daily tasks.

People at the moderate stage of Alzheimer's disease display symptoms such as:

  • Difficulty with some normal daily activities including self-care
  • Increased confusion
  • Increased memory loss
  • May exhibit suspicions of friends and family or delusions
  • Poor judgment

Late Stage

During the late stages of the disease, mental function declines to the point that it has a serious impact on physical functioning. At this point, people lose the ability to converse and carry out movements. They require around-the-clock care and assistance.

Symptoms at this stage include:

  • Difficulty or inability to walk without assistance
  • Difficulty or inability to swallow
  • Loss of awareness of their surroundings
  • May become unable to sit up or hold their head up without assistance
  • Unable to control bladder and bowel functions

According to the Alzheimer's Association, a person with Alzheimer's lives for an average of four to eight years after their diagnosis, but this varies depending on a number of factors and a person may live for 20 years or longer after they are diagnosed.  


There is no simple test that can definitively indicate that a person has Alzheimer's. Doctors will use a number of tests to help diagnose the condition including neurological tests and brain imaging scans.

It is also important to rule out other conditions that may cause symptoms that are similar to Alzheimer's. Your doctor will begin by performing a physical exam, including checking blood pressure and performing a test of your mental status.

A mental status test is used to check your short-term and long-term memory. You may be asked to identify what day it is or to memorize and remember a brief list of words.

Your doctor will also take notes on your medical history. They may ask you questions about your past medical conditions as well as the type of symptoms you are currently experiencing.

A neurological exam may be performed to look at things such as speech, muscle tone, and reflexes. This type of test is used to rule out other conditions such as stroke or infection.

Other types of tests that may be used to diagnose Alzheimer's include:

  • Brain imaging to look for physical changes, anomalies, and activity in the brain, including computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET)
  • Lumbar puncture to look for amyloid and tau proteins
  • Mental status tests to look at things such as language abilities, memory , and problem-solving .
  • Neuropsychological tests to evaluate abilities such as memory, reasoning, attention , and emotional stability


Alzheimer's disease is characterized by specific changes in the brain, primarily an abnormal build-up of certain types of proteins. As the abnormal build-up of proteins lead to tau tangles and amyloid plaques, previously healthy neurons stop functioning. They lose their connections to other neurons and eventually die.

Many of these changes in the brain begin to take place at least a decade or more before the first symptoms of the condition begin to appear.

The exact reasons behind these changes in the brain are not entirely known, but it is believed that a combination of age-related, genetic, environmental, and lifestyle factors may play a role in causing Alzheimer's disease.

The human brain contains billions of nerve cells that communicate with one another to perform a range of functions including thinking and remembering. When proteins build up in the brain, they interfere with the ability of these brain cells to function and progressively cause the death of these cells.

As more cells continue to die, the result is the progressive onset of worsening symptoms that people with Alzheimer's disease experience.

Risk Factors

Factors that may contribute to the onset of the condition include:

  • Age : Advancing age is the most common risk factor for Alzheimer’s disease. According to the National Institute on Aging, approximately a third of all people over the age of 85 have the condition.
  • Being overweight : Being overweight can significantly increase your risk of getting the disease.
  • Brain abnormalities : People who have certain brain abnormalities have a higher risk of developing Alzheimer's as they grow older. The abnormalities are related to the presence of clusters of proteins in the brain, known as plaques and tangles.
  • Family history : Having a family history of the condition may increase your risk of eventually developing it as well.
  • Health conditions : High blood pressure, high cholesterol, diabetes , and smoking are also associated with an increased risk for the disease.
  • Lifestyle factors : Factors such as low physical activity, social engagement, poor sleep , and nutrition habits are associated with a higher risk for developing Alzheimer's.
  • Mental engagement : Mental activity can also play a role in whether you eventually get Alzheimer’s. People who don't engage in activities that are mentally challenging may be more susceptible to getting the condition, although the exact reasons for this are not clear. However, doing things like going to school, learning new things, mentally challenging work , and staying mentally engaged may have a protective effect.
  • Sex : Prevalence rates suggest that women have a higher risk of developing Alzheimer's than men. Research has found that a woman's risk of getting Alzheimer's is around 1.5 to 3 times greater than it is for men. This may be due in part to the fact that women tend to live longer than men.

Estimates suggest that around 5.7 million adults over the age of 65 are living with Alzheimer’s disease in 2018.  


There are two types of Alzheimer’s. Each type is characterized by the age at which symptoms first appear.

Early-Onset Alzheimer’s

In this type, symptoms may first appear when a person is in their 30s, 40s, or 50s. While the disease is often thought of as something that only happens in old age, it can occasionally affect younger people, although this is much less common.

It is unclear what exactly causes early-onset Alzheimer's , but doctors believe it may be due to a rare gene that people inherit.

Late-Onset Alzheimer’s

In late-onset Alzheimer's , which is much more common, symptoms appear at the age of 65 or older. This type of Alzheimer's is much more common and likely the result of a combination of genetic, environmental, and lifestyle factors.

Conditions That Cause Similar Symptoms

It is also important to note that while Alzheimer’s is one of the most common causes of dementia, there are other conditions that can also result in similar symptoms. Other causes include dementia with Lewy bodies, frontotemporal dementia, HIV, Huntington's disease, Parkinson's disease , and traumatic brain injury.


There is no cure for Alzheimer's but there are treatments that may help slow the progression of the disease and make living with the condition more manageable. The treatment that a doctor recommends will depend on the progression of the condition.

Currently, there are medications that may slow clinical decline, treat cognitive symptoms, and treat behavioral symptoms of Alzheimer's.

Slowing Clinical Decline

The drug Aduhelm (aducanumab) is intravenous therapy that has been approved by the Food and Drug Administration (FDA) to treat Alzheimer's disease. It works by targeting and removing amyloid plaques in the brain. According to the FDA, the reduction of these plaques may slow cognitive decline.

Some participants who received Aduhelm experienced improved ability with memory and language; some were able to perform more tasks independently such as household chores.

Side effects of Aduhelm included microhemorrhages (a small amount of blood in the brain tissue), superficial siderosis (excess iron in the brain and spinal cord), headache, fall, diarrhea, and altered mental statuses such as confusion, delirium , or disorientation.

Other potential side effects are amyloid related imaging abnormalities (ARIA). ARIA involves temporary swelling of the brain and may include other symptoms like headache, nausea, vomiting, tremors, vision changes, or gait disturbances.

A doctor must determine if a patient is an eligible candidate for Aduhelm. They first need to determine the presence of amyloid plaques in the brain, so they may conduct a diagnostic test like a cerebral spinal fluid analysis or amyloid PET imaging.

Improving Cognitive Symptoms

Cholinesterase inhibitors work to increase the amount of a neurotransmitter known as acetylcholine. Reduced levels of acetylcholine may be responsible for some of the symptoms of Alzheimer's, so increasing levels of this chemical messenger in your brain may help with memory.

These medications don't stop the decline in cognitive functioning that Alzheimer's causes, but they may help alleviate the symptoms related to memory, language, thinking, and judgment for a certain amount of time.

The most commonly prescribed medications include:

  • Razadyne (galantamine) : Treats mild to moderate Alzheimer's
  • Aricept (donepezil) : Treats all stages of Alzheimer's
  • Exelon (rivastigmine) : Treats mild to moderate Alzheimer's and mild to moderate dementia in Parkinson's disease

Side effects may include nausea or vomiting, loss of appetite, and increased frequency of bowel movements

Glutamate regulators are also used to treat cognitive symptoms. They regulate glutamate, a chemical messenger in the brain, which may improve memory, attention, the ability to reason, language, and the ability to do simple tasks.

Namenda (memantine) is a glutamate regulator that is approved for moderate to severe Alzheimer's. It may cause headaches, constipation, confusion, or dizziness.

A doctor might prescribe a combination of a cholinesterase inhibitor and a glutamate regulator. Namzaric (donepezil and memantine) is approved to treat moderate to severe Alzheimer's. Side effects may include nausea, vomiting, loss of appetite, increased frequency of bowel movements, headache, constipation, confusion, and dizziness.

Improving Behavioral Symptoms

There are many behavioral changes associated with Alzheimer's, but there aren't currently medications to treat each symptom. However, Belsomra (orexin receptor antagonist), is currently approved to treat insomnia specifically in people with mild to moderate Alzheimer's disease.

Side effects may include impaired alertness and motor coordination, worsened depression or suicidal ideation , sleep-walking, sleep paralysis, and compromised respiratory function.

Current medications to treat Alzheimer's disease focus on slowing the progression and alleviating symptoms of existing conditions. Researchers are still working toward developing future treatments that may prevent people from developing Alzheimer's.


An Alzheimer's diagnosis can be stressful for both the person who has the condition and their loved ones. In addition to drug therapies, there are also lifestyle and behavioral strategies that can help people manage the condition as it progresses.

Expect Challenges

Try not to get frustrated when your loved one forgets or misunderstands something. Focus on being as clear as you can, eliminate distractions, and repeat things if you need to.

Focus on Safety

As Alzheimer's disease progresses, the individual may face dangers that you did not anticipate. Even normal daily activities can present hazards, so focus on keeping the environment safe based on the individual's current level of functioning. This might involve removing sharp objects and keeping doors and windows locked to prevent unexpected wandering.

Look for Reasons Behind Behaviors

In some cases, a person may act out with agitation or anxiety if one of their needs is unmet but they are unable to communicate these needs. When such behaviors arise, consider some of the reasons behind them. It might indicate a need for something whether it means going for a walk or having something to eat.

A Word From Verywell

Learning more about the disease's progression, exploring strategies to deal with the different stages of the disease, and finding ways for caregivers to cope are all important.

If you are caring for a loved one with Alzheimer's, seek support from others such as joining a support group or finding healthcare resources in your community that can help.

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Verywell Mind 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 Kendra Cherry
Kendra Cherry, MS, is the author of the "Everything Psychology Book (2nd Edition)" and has written thousands of articles on diverse psychology topics. Kendra holds a Master of Science degree in education from Boise State University with a primary research interest in educational psychology and a Bachelor of Science in psychology from Idaho State University with additional coursework in substance use and case management.