Alzheimer's Disease

Alzheimer’s disease is a brain disorder that slowly destroys memory and thinking skills, and eventually, the ability to carry out the simplest tasks.

Overview

Alzheimer’s disease is the most common cause of dementia among older adults. Dementia is the loss of the ability to think, remember, and reason — to the point where it gets in the way of daily life.

Experts suggest that millions of Americans, most of them age 65 or older, may have Alzheimer’s. It is among the leading causes of death in the United States.

Alzheimer’s disease is named after Dr. Alois Alzheimer. In 1906, Dr. Alzheimer noticed changes in the brain tissue of a woman who had died of an unusual mental illness. Her symptoms included memory loss, language problems, and unpredictable behavior. After she died, he examined her brain and found two types of abnormalities that are now considered hallmarks of Alzheimer’s disease. One was many abnormal clumps of a protein called amyloid-beta. These clumps are now called amyloid plaques. The other strange characteristic of the patient’s brain was tangled bundles of fibers made up of a protein called tau. These are now referred to as either neurofibrillary tangles or tau tangles.

Brain changes in Alzheimer’s begin a decade or more before symptoms appear. During this very early stage, changes linked to Alzheimer’s can build up in the brain, including the formation of amyloid plaques and tau tangles. Healthy neurons stop working, lose connections with other neurons, and die.

The damage first appears in the hippocampus and the entorhinal cortex — parts of the brain essential for forming memories. As more neurons die, additional parts of the brain are affected and begin to shrink. By the final stage of Alzheimer’s, damage is widespread and brain tissue has shrunk significantly.

Signs and Symptoms

Brain changes associated with Alzheimer’s disease begin years before symptoms appear. Over time symptoms progress from mild to moderate to severe.

Before Symptoms Appear

Research has shown that brain changes linked to Alzheimer’s start a decade or more before memory and thinking problems appear. Not everyone with these brain changes develops dementia.

Mild Cognitive Impairment

Mild cognitive impairment is a condition in which people have more memory problems than normal for their age but are still able to carry out their normal daily activities. People with mild cognitive impairment are at a greater risk for developing Alzheimer’s disease, so it’s important to see a doctor or specialist regularly if you have this condition.

Mild Alzheimer’s Disease

During mild Alzheimer’s, people experience greater memory loss and other thinking difficulties. Other problems can include:

  • Losing track of dates or knowing current location
  • Taking longer to complete normal daily tasks
  • Repeating questions or forgetting recently learned information
  • Trouble handling money and paying bills
  • Wandering and getting lost
  • Mood and personality changes
  • Increased anxiety

Alzheimer’s is often diagnosed at this stage.

Moderate Alzheimer’s Disease

In this stage, increasing damage occurs in brain areas that affect language, reasoning, and ability to carry out daily activities. Symptoms worsen and may include:

  • Increased confusion and memory loss
  • Inability to learn new things
  • Difficulty carrying out multistep tasks, such as getting dressed
  • Occasional problems recognizing family and friends
  • Hallucinations, delusions, and paranoia
  • Impulsive behavior
  • Restlessness, agitation, and anxiety, especially in the late afternoon or evening
  • Depression
  • Disrupted sleep

Severe Alzheimer’s Disease

During this stage, damage spreads throughout the brain and the brain shrinks significantly. The affected person may have very limited ability to communicate and usually needs full-time help with daily care. Other symptoms often include:

  • Lack of awareness of recent experiences or surroundings
  • Weight loss with little interest in eating
  • Seizures
  • Difficulty swallowing, which can increase the risk of aspiration (breathing food or liquid into the lungs) and pneumonia
  • Loss of bowel and bladder control
  • Sleep disruption

Causes and Risk Factors

Scientists don’t yet fully understand what causes Alzheimer’s disease in most people. The causes probably include a combination of age-related changes in the brain, along with genetic, environmental, and lifestyle factors.

Age

Age is the biggest known risk factor for Alzheimer’s disease. Most people with Alzheimer’s develop the disease when they are 65 or older. Risk increases with age, especially after age 65. A small percentage of people develop symptoms before age 65 (often estimated around 5% to 10%). When the disease develops before age 65, it is called early-onset Alzheimer’s.

Age-related brain changes that may contribute to Alzheimer’s include:

  • Accelerated shrinkage of certain brain areas
  • Inflammation
  • Blood vessel damage
  • Production of unstable molecules called free radicals
  • Decreased energy production within cells

Genetics

In most cases, Alzheimer’s does not have a single genetic cause. Instead, it can be influenced by multiple genes in combination with lifestyle and environmental factors. People who have a parent or sibling diagnosed with Alzheimer’s have a higher risk of developing the disease than those who don’t have a close relative with it.

Scientists have identified many genetic changes linked to Alzheimer’s risk. Of those, rare mutations in three genes are known to cause the disease: APP, PSEN1, and PSEN2. A child whose biological parent carries a mutation in one of these three genes has a 50% chance of inheriting it. If inherited, these rare gene variants greatly increase the likelihood of developing Alzheimer’s, often before age 65.

Another gene, APOE, also influences Alzheimer’s risk. The APOE ε4 form increases a person’s risk and is associated with an earlier average age of symptom onset for certain populations, but it does not mean someone will definitely develop Alzheimer’s. The APOE ε2 form may provide some protection against Alzheimer’s.

In addition, the genetic condition known as Down syndrome influences the risk of developing Alzheimer’s disease. Many people living with Down syndrome will develop Alzheimer’s dementia, with symptoms appearing in their 50s or 60s.

Health and Lifestyle Factors

Research suggests that several factors beyond genetics may play a role in the development of Alzheimer’s. These include:

Several health conditions also may influence risk for Alzheimer’s disease, including:

Prevention Guidance

There are some risk factors, like age and genetics, that you cannot change. However, there may be ways to promote better brain health and reduce your risk of Alzheimer’s by addressing certain lifestyle factors.

Researchers cannot yet say for certain whether making positive changes in these areas can prevent dementia, but doing so is beneficial to living a healthier lifestyle overall. Steps that may help include:

  • Eating a healthy diet
  • Staying physically active
  • Staying socially engaged
  • Keeping your mind active with mentally stimulating activities
  • Managing chronic health conditions such as high blood pressure and hearing loss
  • Getting enough sleep
  • Avoiding smoking and limiting alcohol
  • Getting recommended health screenings and regularly checking in with a healthcare provider

If you, a family member, or a friend has problems remembering recent events or thinking clearly, talk with a doctor. People with memory and thinking concerns should talk to their doctor to find out whether their symptoms are due to Alzheimer’s or to another cause.

Diagnosis

Doctors use several methods and tools to help determine whether a person who is having memory problems has Alzheimer’s. They may:

  • Ask questions about overall health, medicines, diet, past medical problems, ability to carry out daily activities, and changes in behavior and personality
  • Conduct tests of memory, problem solving, attention, counting, and language — these tests may be repeated over time to track how a person’s memory and other thinking skills are changing
  • Order blood, urine, and other standard medical tests to eliminate other possible causes of symptoms
  • Administer tests to check for depression or another mental health condition
  • Order a blood test to measure levels of proteins linked to Alzheimer's and if needed order a spinal tap.

Doctors may also perform brain scans to support an Alzheimer’s diagnosis or to rule out other possible causes of symptoms. Types of brain scans include:

Who Can Diagnose Alzheimer’s Disease?

Visiting a primary care doctor is often the first step. However, neurologists — doctors who specialize in disorders of the brain and nervous system — are often consulted to diagnose dementia. Geriatric psychiatrists, neuropsychologists, and geriatricians may also be able to diagnose dementia. Your primary care doctor can help you find a specialist. If a specialist cannot be found in your community, contact the nearest medical school neurology department for a referral.

Treatment and Management

There is currently no cure for Alzheimer’s. However, some newer medicines can slow the worsening of symptoms in some people with early Alzheimer’s.

Two medicines that target amyloid plaques, lecanemab and donanemab, received full approval full approval by the U.S. Food and Drug Administration (FDA) for the treatment of early Alzheimer’s. These drugs reduce the buildup of amyloid in the brain. Clinical trials have shown that they can slow the progress of cognitive decline in some people and require careful monitoring for side effects.

There are also medicines that may temporarily improve or stabilize memory and thinking skills in some people and may help manage certain symptoms and behavioral problems.

Antidepressants, antipsychotics, and anti-anxiety drugs may be helpful for some people with Alzheimer’s who experience sleeplessness, depression, anxiety, and agitation. However, experts agree that these medicines should be used only after other strategies to promote physical and emotional comfort, such as avoiding stressful situations, have been tried. When these medicines are prescribed, patients should be monitored by their doctor, because they can have serious side effects.

Living With Alzheimer’s Disease

An early diagnosis helps families plan for the future. Families can take care of financial and legal matters, address potential safety issues, learn about living arrangements, and develop support networks.

In the early stages of dementia, it may be possible for people to continue with their everyday activities. Changes to the home environment and daily activities may help a person manage their changes in thinking. As the disease progresses, people will need to adopt new strategies to help adjust.

Caring for a person with Alzheimer’s can have significant physical, emotional, and financial costs. Programs that teach families about the various stages of Alzheimer’s and about ways to deal with difficult behaviors and other caregiving challenges can help.

Good coping skills, a strong support network, and respite care are other things that may help caregivers handle the stress of caring for a loved one with Alzheimer’s. For example, staying physically active provides physical and emotional benefits.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find clinical trials on Alzheimer’s disease.

Alzheimers.gov also has a section on learning more about clinical trials and how to find them.

You can also check out this NIH video series on volunteering for Alzheimer’s clinical trials.

Find Treatment

To learn more about Alzheimer’s clinical trials and studies:

Finding Support as a Caregiver

Some caregivers for people with Alzheimer’s disease have found that joining a support group is a critical lifeline. These support groups enable caregivers to find respite, express concerns, share experiences, get tips, and receive emotional comfort. Many organizations sponsor in-person and online support groups, including groups for people with early-stage Alzheimer’s and their families.

You can visit the Eldercare Locator, a service of the Administration for Community Living to connect you to services for older adults and their families.

You can find more information about Alzheimer’s disease at:

Note: This resource list is for informational purposes only. It is not comprehensive, and an organization’s inclusion does not constitute an endorsement by NIH.  

Research Information

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.  

NIH funds Alzheimer’s Disease Research Centers throughout the United States that conduct a wide range of research, including trials and studies of the causes, diagnosis, and management of the disease.

NIH funded scientists are conducting studies to understand the root causes of Alzheimer' and the very complex biological features of the disease. Advances in brain imaging techniques enable researchers to see the development and spread of abnormal amyloid and tau proteins in the living brain, as well as changes in brain structure and function.

Scientists are also exploring the very earliest steps in the disease process by studying changes in the brain and body fluids that can be detected years before Alzheimer’s symptoms appear.

Another major focus of NIH funded research is the development and testing of new drugs that target the many different biological features of the disease. For example, they are developing drugs that target chronic brain inflammation that leads to damage of nerve cells.

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.  

Brain Donation

Sometimes, a person with dementia, after discussing the option with their loved ones, will decide to donate their brain after they die. Brain donation is voluntary and ensures anonymity of the donor. Brain donation helps researchers study brain disorders such as Alzheimer’s disease and related dementias. When donating as part of a research study or to the NIH NeuroBioBank, there is no cost to the family for the donation and an autopsy report.

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