What Is Alzheimer’s Disease? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Alzheimer’s disease is a progressive, irreversible brain disorder that slowly destroys memory and cognition — the ability to think and reason.

Alzheimer’s disease is the most common form of dementia among older adults. Most people with this disorder are 65 or older, but it can also begin at an earlier age, according to the National Institute on Aging.

While there is currently no cure for Alzheimer’s, there are medications that improve symptoms and delay progression into the later stages of the disease.

Scientists are working to understand the biological pathways behind Alzheimer’s disease, with the goal of finding new and better treatments and ways to further delay or prevent Alzheimer’s disease.

Alzheimer’s and the Brain

Alzheimer’s disease is named for a German psychiatrist and neuropathologist named?Alois Alzheimer. While conducting an autopsy in 1906, the doctor noticed abnormalities in the brain of a woman with a mysterious illness that caused memory loss, language problems, unpredictable behavior, and, ultimately, death.

The woman’s brain, Alzheimer reported, had many abnormal protein clumps (now called amyloid plaques) as well as tangled bundles of fibers (now called neurofibrillary tangles composed of tau, another type of protein). Those plaques and tangles are the hallmarks of Alzheimer’s disease.

Alzheimer’s disease causes nerve cells (neurons) to stop functioning, lose their connections with other neurons, and die.

Typically, the damage first affects the parts of the brain that form memories. Eventually, neurons in other areas of the brain also begin to die, causing progressive symptoms of memory loss, other thinking problems, neuropsychiatric issues, and changes in function.

The Role of Plaques and Tangles

Amyloid accumulates into toxic species, or variants — tiny little clusters called oligomers and protofibrils ?— eventually coalescing into plaques. Amyloid causes Alzheimer’s disease by making nerve cells dysfunction, permitting tau tangles to spread in the brain.

In healthy brain tissue, the protein known as tau stabilizes the transport and scaffolding systems that supply cells with nutrients and other important substances. But when tau forms tangles, cells can’t get the essentials they need and begin to die.

Signs and Symptoms of Alzheimer’s Disease

While a certain amount of forgetfulness — losing things from time to time, sometimes forgetting which word to use — is a normal part of aging, certain types of memory loss can indicate either the possibility or the presence of early-stage Alzheimer’s disease.

Scientists have identified a condition called mild cognitive impairment (MCI) that for some (not all) people is an early sign of Alzheimer’s disease. MCI involves problems with memory or mental function that are noticeable to the person affected but not serious enough to interfere with everyday life.

People with MCI may be at higher risk of developing Alzheimer’s or other forms of dementia than people who don’t have MCI. But MCI doesn’t always progress, and some people even get their cognitive abilities back.

Signs and Symptoms of Early-Stage Alzheimer’s Disease

Symptoms of Alzheimer’s disease are generally mild at first, but become more noticeable as the disease progresses. The person may begin having difficulty with:

  • Memory Losing items like keys around the house, forgetting a friend’s name or a recent conversation, getting lost in a familiar place
  • Speech Repeating oneself or struggling to follow a conversation
  • Visual Perception Difficulty seeing things in three dimensions or judging distances
  • Concentrating, Organizing, or Planning Struggling to make decisions, solve problems, or complete multistep tasks, such as cooking a meal
  • Orientation Getting confused about location, time, or date
  • Mood Feeling anxious, depressed, or irritable

Signs and Symptoms of Later-Stage Alzheimer’s Disease

As the disease becomes more advanced, symptoms seen in early-stage disease become more pronounced. People may also experience:

  • Delusions For instance, believing without reason that someone is stealing from them
  • Uncharacteristic Behavior Exhibiting aggression or agitation, calling out, or having disturbed sleep patterns
  • Difficulty Walking Becoming bedridden or wheelchair-bound and requiring round-the-clock care to help with daily tasks
  • Increased Difficulty Communicating Failing to understand what others are saying, not being able to respond, and largely ceasing to speak

Causes and Risk Factors of Alzheimer’s Disease

What causes Alzheimer’s? That is the billion-dollar question of dementia research. Scientists have made progress in understanding what happens in the brain as the disease progresses, but they still don’t know just what kicks off these changes.

Researchers believe that the vast majority of Alzheimer’s cases are due to some combination of genetics, lifestyle, and environment. Risk factors include:

  • Age Alzheimer’s disease is not a normal part of aging, but the risk for it increases with age beyond 65.
  • Family History Having a first-degree relative (such as a parent or sibling) with the disease is a strong risk factor. This may reflect shared genetics, environmental factors, or both.
  • Genetics One gene variant, called APOE-e4, appears to significantly raise a person’s Alzheimer’s risk. But some people with APOE-e4 never develop Alzheimer’s, while others who develop Alzheimer’s don’t have the gene variant.
Risk factors for Alzheimer’s that may be somewhat under a person’s control include:

  • Head Injury Researchers have identified a link between traumatic brain injury and different types of dementia, including Alzheimer’s. Wearing a seat belt in a car or a helmet while playing certain kinds of sports or minimizing the risk of falling in your home can offer protection.
  • Cardiovascular Problems When your heart or blood vessels are damaged or diseased, your body is unable to pump enough blood to your brain, depriving cells of the oxygen they need to function. Conditions like?heart disease, stroke, high blood pressure, high cholesterol, and diabetes may raise your Alzheimer’s risk.
  • Poor Overall Health Researchers believe that poor overall health — linked to habits like smoking, being sedentary, or following an unhealthy diet — may increase Alzheimer’s risk.

Is Alzheimer’s Hereditary?

As mentioned above, the genes you inherit from your parents can raise your risk of developing Alzheimer’s. The APOE gene raises risk quite a bit.

Other genes directly cause Alzheimer’s and are passed directly from parent to child. This form is known as familial Alzheimer’s disease. It accounts for less than 1 percent of all Alzheimer’s cases, according to the Alzheimer’s Society. Those cases almost always involve early-onset Alzheimer’s disease, an uncommon presentation in which it develops before age 65. These genes cause Alzheimer’s disease by increasing the formation of amyloid.

Having Down syndrome raises the risk of developing Alzheimer’s disease for genetic, but not hereditary, reasons. People with Down syndrome are born with an extra full or partial copy of chromosome 21, which carries a gene that produces a protein called amyloid precursor protein (APP). Too much APP leads to a buildup of beta-amyloid plaques in the brain.

By age 40, most people with Down syndrome have significant levels of beta-amyloid plaques, along with tau tangles, in their brains. About half of people with Down syndrome develop dementia due to Alzheimer’s as they age, usually when they’re in their fifties and sixties.

Alzheimer’s disease associated with Down syndrome is not passed down from parent to child.

How Is Alzheimer’s Disease Diagnosed?

There is no single test that can determine if a person has Alzheimer’s disease. Instead, doctors may use a number of diagnostic methods:

  • Medical history
  • Physical exam and diagnostic tests
  • Neurological exam
  • Mental status tests
  • Brain imaging

Medical History

Healthcare practitioners ask about current and past symptoms, illnesses, and medications and inquire about health issues affecting family members, such as Alzheimer’s and other forms of dementia.

Physical Exam and Diagnostic Tests

Doctors listen to your heart and lungs and examine other relevant areas of the body. They may also collect blood and urine samples for lab testing and perform additional assessments to help identify ailments that may cause dementia-like symptoms (such as depression, untreated sleep apnea, delirium, certain vitamin deficiencies, side effects of medication, thyroid problems, or excess alcohol use).

A lumbar puncture can be done to measure the amyloid and tau levels in spinal fluid; this test can help to identify most people with Alzheimer’s disease.

Neurological Exam

A neurological exam that tests strength, sensation, reflexes, and eye movements can evaluate for medical conditions that may lead to impaired memory and cognition, like stroke or Parkinson’s disease.

Mental Status Tests

This type of testing assesses memory, ability to solve simple problems, and other cognitive skills. During a test called the Mini-Cog, for instance, you’re asked to remember and, a few minutes later, repeat the names of three common objects. The doctor will also ask questions to determine whether you could have a mood disorder with symptoms that mimic Alzheimer’s disease.

Brain Imaging

A brain scan, such as a magnetic resonance imaging (MRI) or computerized tomography (CT) scan, may be used to rule out the presence of a tumor or another abnormality that could be responsible for Alzheimer’s-like symptoms. An amyloid positron emission tomography (PET) scan can reveal beta-amyloid plaques in the brain.

What Are the 7 Stages of Alzheimer’s Disease?

There are a number of different ways to describe the progression of Alzheimer’s disease. Although many experts use just three overall terms — “mild,” “moderate,” and “severe” — another commonly used guideline breaks these categories down further into seven stages, according to the Fisher Center for Alzheimer’s Research:

  • Stage 1: Normal
  • Stage 2: Normal age-related forgetfulness
  • Stage 3: Mild cognitive impairment
  • Stage 4: Mild Alzheimer’s disease
  • Stage 5: Moderate Alzheimer’s disease
  • Stage 6: Moderately severe Alzheimer’s disease
  • Stage 7: Severe Alzheimer’s disease

Stage 1: Normal

People of any age can be free of any signs of cognitive or functional decline or associated changes in behavior or mood. These mentally healthy people belong in this “normal” stage 1 category.

Stage 2: Normal Age-Related Forgetfulness

Many adults age 65 and older believe their memory is slipping a bit — that they have more trouble remembering names than they used to, for instance. But other people may not notice these changes, and they’re unlikely to cause concern even if others do notice.

Stage 3: Mild Cognitive Impairment

Memory problems are subtle but significant enough for close friends and family to notice. The person might ask the same question repeatedly or have trouble acquiring new skills or performing tasks involving a series of steps.

Stage 4: Mild Alzheimer’s Disease

Someone at this stage may become increasingly unable to handle the more complex demands of daily life, such as ordering from a menu at a restaurant.

Stage 5: Moderate Alzheimer’s Disease

The basic demands of everyday life, such as picking out clothing suitable for the weather, become difficult. The person may not be able to remember the name of the president or count backwards from 20 by twos.

Stage 6: Moderately Severe Alzheimer’s Disease

The person may have trouble walking?or putting on their clothing correctly and become reliant on caregivers for help with bathing and using the toilet. The end of this stage is marked by incontinence (inability to control urination or bowel movements) and inability to speak coherently.

Stage 7: Severe Alzheimer’s Disease

Speech is essentially lost. The person loses their ability to walk or sit up independently, to smile, and to hold their head up without assistance. Physical rigidity sets in.

Prognosis of Alzheimer’s Disease

There’s no cure for Alzheimer’s disease, and current treatments can only slow its progression — meaning that the person’s cognitive decline continues until death. But especially in its earlier stages, Alzheimer’s related cognitive decline may be slowed by lifestyle measures like staying physically active and socially engaged and following a healthy diet.

Duration of Alzheimer’s Disease

The brain changes that happen in Alzheimer’s disease may begin a decade or more before the first symptoms appear — as amyloid plaques and tau tangles start to form, neurons die, and other toxic changes in the brain occur.

After the onset of memory problems , a person with Alzheimer’s will live 10 to 20 years.

Treatment and Medication Options for Alzheimer’s Disease

While there is currently no cure for Alzheimer’s disease, certain treatments can slow cognitive decline for a limited time, help manage behavioral symptoms, and provide relief for symptoms like anxiety and depression.

Disease-Modifying Drugs

Two drugs, lecanemab (Leqembi) and donanemab (Kisunla), address the underlying biology of the disease by removing beta-amyloid clumps from the brain. The drugs have been shown to slow the progression of cognitive decline when they’re started in early-stage Alzheimer’s. Both can cause brain swelling and bleeding as a side effect.

Medications for Symptoms

A number of other drugs are approved to treat cognitive symptoms of Alzheimer’s disease. These drugs are believed to work by altering levels of neurotransmitters (chemical messengers) in the brain. These include:

Doctors may also prescribe drugs for people experiencing behavioral symptoms of Alzheimer’s, targeting conditions such as depression, aggression, restlessness, and anxiety.

The drug brexpiprazole (Rexulti) is approved to treat agitation in Alzheimer’s, and the drug suvorexant (Belsomra) is approved to treat insomnia in people with Alzheimer’s.

Research efforts on new Alzheimer’s treatments have been frustrating, with promising drug candidates often failing in clinical trials. But scientists are continuing to explore new interventions, according to the National Institute on Aging.

Nondrug Approaches

Whether or not a person with Alzheimer’s is being treated with medications, they can generally benefit physically and mentally from involvement in support groups, social outings geared toward people with dementia, and activities like dancing that combine social, mental, and physical engagement. In earlier stages of the disease, meeting with a psychotherapist may be helpful for coming to terms with the diagnosis and improving coping skills.

Complementary Treatments

Despite the growing number of herbal remedies, dietary supplements, and “medical foods” aimed at people with Alzheimer’s, there is no scientific proof that any of these products work.

For instance, some people with Alzheimer’s disease consume coconut oil based on the theory that the caprylic acid in the oil can provide energy to brain cells that are no longer able to metabolize glucose. But there has been no research confirming that this helps cognition.

There is evidence, though, that following an overall healthy diet may reduce the risk of developing Alzheimer’s disease and other forms of dementia.

Complications of Alzheimer’s Disease

In advanced stages of Alzheimer’s disease, complications from severe loss of brain function can include dehydration, malnutrition, or infection.

One common Alzheimer’s complication is difficulty swallowing (dysphagia), which can result in food or drink being aspirated (breathed) into the lungs, potentially causing pneumonia. Pneumonia is a common cause of death for people with severe Alzheimer’s.

Prevention of Alzheimer’s Disease

Can a healthy lifestyle reduce Alzheimer’s risk? A growing body of research suggests it can.

For instance, one study found that even people at high genetic risk of dementia could reduce their risk by pursuing a healthy lifestyle that involved:

  • Not smoking
  • Exercising regularly
  • Eating a healthy diet
  • Consuming alcohol only moderately
You may also reduce your Alzheimer’s and dementia risk by being socially active, maintaining a healthy body weight, and getting quality sleep.

Research and Statistics: How Many People Have Alzheimer’s?

The Alzheimer’s Association estimates that 6.9 million people in the United States are living with Alzheimer’s disease, including about 1 in 9 people age 65 or older.

The percentage of people with Alzheimer’s increases with age. For example, 5.0 percent of people ages 65 to 74 have the disease, which rises to 13.2 percent of people ages 75 to 84 and 33.4 percent of people age 85 and older.

As the number of older Americans rises, the number of people with Alzheimer’s disease in the United States is expected to more than double by 2050, barring any significant medical breakthroughs.

Disparities and Inequities in Alzheimer’s

Among U.S. residents, there are striking differences in the risk of developing Alzheimer’s disease depending on a person’s sex, race, and ethnicity, according to the Alzheimer’s Association.

Nearly two-thirds of people with Alzheimer’s in the United States are women, largely because women tend to live longer than men, and older age is a major risk factor for Alzheimer’s disease. It’s estimated that 11 percent of women ages 65 and older have Alzheimer’s, compared with 9 percent of men.

Some researchers have pointed out that the higher risk for Alzheimer’s among women may reflect “survival bias” — since men are more likely than women to die from cardiovascular causes before age 65, those who survive past that age reflect a healthier subset of men who are also less likely to develop Alzheimer’s and other forms of dementia.

A number of studies have shown, however, that Black and Hispanic older adults are more likely to develop Alzheimer’s than their white counterparts — one study showed that among Americans ages 65 and older, the prevalence of Alzheimer’s was 10 percent for white older adults, 14 percent for Hispanic older adults, and 19 percent for Black older adults. These differences are not believed to reflect any genetic differences in Alzheimer’s risk. Instead, researchers believe they reflect differences in factors like educational and social opportunities, nutrition, healthcare access, and exposure to pollution.

There isn’t much data on Alzheimer’s risk among other racial or ethnic groups, but one study of California residents found that American Indian and Native Alaskan older adults had a risk level similar to that of white older adults, while Asian American older adults had the lowest risk for Alzheimer’s disease.

What Is the Difference Between Alzheimer’s Disease and Dementia?

Although the terms “dementia” and “Alzheimer’s disease” are sometimes used interchangeably, they are not the same thing.

Dementia isn’t a specific disease, but rather a general term to describe any decline in brain function that affects memory, language, and other cognitive abilities and is serious enough to interfere with daily life.

Alzheimer’s disease is the most common type of dementia, accounting for 60 to 80 percent of all dementia cases.

Related Conditions

It is very common for people with Alzheimer’s disease to also experience brain abnormalities related to other types of dementia, a condition called mixed dementia.

Other types of dementia include:

  • Vascular Dementia The most commonly seen type of mixed dementia involves Alzheimer’s with vascular dementia, in which brain cells are deprived of essential nutrients and oxygen because of conditions that block or reduce blood flow to the brain.
  • Lewy Body Dementia People with Alzheimer’s may also experience Lewy body dementia, a disease marked by abnormal clumps of the protein alpha-synuclein in brain cells.
Some people may experience brain changes related to all three conditions at the same time — Alzheimer’s, vascular dementia, and Lewy body dementia.

Living With Alzheimer’s

Preserving quality of life for as long as possible is a widespread goal for people living with Alzheimer’s disease. The key is having strategies in place to maximize independence, minimize frustration, and build feelings of confidence and emotional connection that help make every day the best it can be.

Routines can ease the burden of short-term memory loss for people in the earlier stages of dementia. If you have Alzheimer’s, you might feel calmer and more in control knowing that your house keys are always on a hook by the door, for example, or that your caregiver always records appointments on a wall calendar.

As Alzheimer’s disease progresses, people often have more difficulty expressing their wants and needs to others. If you are a caregiver, there are strategies that can help you and the person you care for meet this challenge.

Keeping the mood positive, reducing distractions like TV, and making your questions easy to answer with a “yes” or “no” can all make a huge difference. Sometimes body language and nonverbal cues can express what words no longer can, notes the Family Caregiver Alliance.

Early-Onset Alzheimer’s

Early-onset Alzheimer’s describes Alzheimer’s disease in people younger than 65.

It’s unclear how many people with Alzheimer’s have early-onset disease, according to the Alzheimer’s Association. But many of these people develop the disease in their forties and fifties, which can make getting an accurate diagnosis difficult and frustrating.

In a few hundred families around the world, early-onset Alzheimer’s is caused by a specific genetic variant (mutation). This rare condition is known as familial Alzheimer’s disease and tends to affect many family members across generations.

For everyone else with early-onset Alzheimer’s, the same risk factors as those for late-onset Alzheimer’s come into play: genetics, lifestyle, and environmental influences interacting in complicated and still not fully understood ways.

Common Questions & Answers

What’s the difference between Alzheimer’s disease and dementia?

Dementia is a broad term that refers to significant cognitive impairment from any cause. Alzheimer’s disease is the leading cause of dementia among older adults and involves a specific pattern of changes in the brain that leads to cognitive decline.

Who is at risk for Alzheimer’s disease?

Older age is the most clearly established risk factor for Alzheimer’s. It’s much more common in adults age 65 and older, and the risk increases with age within this group. Other factors that may affect your risk for Alzheimer’s include a family history of the disease, your cardiovascular health, and lifestyle measures in areas like nutrition, physical activity, and sleep quality.

What are the symptoms of Alzheimer’s disease?

The process underlying Alzheimer’s disease can take decades, so it’s unlikely you’ll experience sudden changes in your cognitive abilities. But people who are developing Alzheimer’s may first experience greater forgetfulness, followed by more significant changes in memory, speech, judgment, ability to concentrate, and awareness of time and location.

Can Alzheimer’s disease be treated?

While there are treatments for Alzheimer’s disease, none of them can stop the condition — they can, at best, slow down the rate of cognitive decline and are most effective in early stages of Alzheimer’s. But as researchers learn more about the disease, they’re hopeful that more effective treatments and, eventually, a cure will emerge.

Can Alzheimer’s disease be prevented?

You may be able to reduce your risk for Alzheimer’s by taking care of your health in general — following a healthy lifestyle and effectively managing conditions like high blood pressure or diabetes. But there is no clear path to ensure that you don’t develop Alzheimer’s disease.

The Takeaway

Alzheimer’s disease is a serious brain disorder that leads to memory loss and other forms of cognitive and (eventually) physical decline. While there’s currently no cure, managing risk factors like high blood pressure, a sedentary lifestyle, and smoking may help to prevent it, and medications can slow its progression. If you’re concerned about forgetfulness, increased difficulty performing familiar tasks, or any other problems related to thinking or memory, seek advice and cognitive screening from a healthcare provider early on.

Resources We Trust

Editorial Sources and Fact-Checking

Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.

Sources

  1. Alzheimer’s Disease Fact Sheet. National Institute on Aging. April 5, 2023.
  2. Inside the Brain. Alzheimer’s Association.
  3. Mild Cognitive Impairment (MCI). Mayo Clinic. February 13, 2024.
  4. What Are the Signs of Alzheimer’s Disease? National Institute on Aging. October 18, 2022.
  5. Alzheimer’s Disease. Mayo Clinic. February 13, 2024.
  6. What Are the Causes and Risk Factors of Alzheimer’s and Other Dementias? Alzheimer’s Association.
  7. What Causes Young-Onset Dementia? Alzheimer’s Society.
  8. Alzheimer’s Disease in People With Down Syndrome. National Institute on Aging. November 30, 2020.
  9. Down Syndrome and Alzheimer’s Disease. Alzheimer’s Association.
  10. Medical Tests for Diagnosing Alzheimer’s. Alzheimer’s Association.
  11. Clinical Stages of Alzheimer’s. The Fisher Center for Alzheimer’s Research Foundation.
  12. What Is Alzheimer’s Disease? Alzheimer’s Association.
  13. Medications for Memory, Cognition and Dementia-Related Behaviors. Alzheimer’s Association.
  14. How Is Alzheimer’s Disease Treated? National Institute on Aging. September 12, 2023.
  15. Treatment and Support of Alzheimer’s Disease. Alzheimer’s Society. April 13, 2023.
  16. Alternative Treatments. Alzheimer’s Association.
  17. Alzheimer’s Stages: How the Disease Progresses. Mayo Clinic. June 7, 2023.
  18. Lourida I et al. Association of Lifestyle and Genetic Risk With Incidence of Dementia. JAMA. July 14, 2019.
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