Alzheimer's disease

Last updated February 19, 2022

Alzheimer's disease is a progressive neurologic disorder that causes the brain to shrink (atrophy) and brain cells to die. Alzheimer's disease is the most common cause of dementia — a continuous decline in thinking, behavioral and social skills that affects a person's ability to function independently.

Approximately 5.8 million people in the United States age 65 and older live with Alzheimer's disease. Of those, 80% are 75 years old and older. Out of the approximately 50 million people worldwide with dementia, between 60% and 70% are estimated to have Alzheimer's disease.

The early signs of the disease include forgetting recent events or conversations. As the disease progresses, a person with Alzheimer's disease will develop severe memory impairment and lose the ability to carry out everyday tasks.

Medications may temporarily improve or slow progression of symptoms. These treatments can sometimes help people with Alzheimer's disease maximize function and maintain independence for a time. Different programs and services can help support people with Alzheimer's disease and their caregivers.

There is no treatment that cures Alzheimer's disease or alters the disease process in the brain. In advanced stages of the disease, complications from severe loss of brain function — such as dehydration, malnutrition or infection — result in death.

Symptoms

Memory loss is the key symptom of Alzheimer's disease. Early signs include difficulty remembering recent events or conversations. As the disease progresses, memory impairments worsen and other symptoms develop.

At first, a person with Alzheimer's disease may be aware of having difficulty remembering things and organizing thoughts. A family member or friend may be more likely to notice how the symptoms worsen.

Brain changes associated with Alzheimer's disease lead to growing trouble with:

Memory

Everyone has occasional memory lapses, but the memory loss associated with Alzheimer's disease persists and worsens, affecting the ability to function at work or at home.

People with Alzheimer's may:

Repeat statements and questions over and over
Forget conversations, appointments or events, and not remember them later
Routinely misplace possessions, often putting them in illogical locations
Get lost in familiar places
Eventually forget the names of family members and everyday objects
Have trouble finding the right words to identify objects, express thoughts or take part in conversations

Thinking and reasoning

Alzheimer's disease causes difficulty concentrating and thinking, especially about abstract concepts such as numbers.

Multitasking is especially difficult, and it may be challenging to manage finances, balance checkbooks and pay bills on time. Eventually, a person with Alzheimer's may be unable to recognize and deal with numbers.

Making judgments and decisions

Alzheimer's causes a decline in the ability to make reasonable decisions and judgments in everyday situations. For example, a person may make poor or uncharacteristic choices in social interactions or wear clothes that are inappropriate for the weather. It may be more difficult to respond effectively to everyday problems, such as food burning on the stove or unexpected driving situations.

Planning and performing familiar tasks

Once-routine activities that require sequential steps, such as planning and cooking a meal or playing a favorite game, become a struggle as the disease progresses. Eventually, people with advanced Alzheimer's often forget how to perform basic tasks such as dressing and bathing.

Changes in personality and behavior

Brain changes that occur in Alzheimer's disease can affect moods and behaviors. Problems may include the following:

Depression
Apathy
Social withdrawal
Mood swings
Distrust in others
Irritability and aggressiveness
Changes in sleeping habits
Wandering
Loss of inhibitions
Delusions, such as believing something has been stolen

Preserved skills

Many important skills are preserved for longer periods even while symptoms worsen. Preserved skills may include reading or listening to books, telling stories and reminiscing, singing, listening to music, dancing, drawing, or doing crafts.

These skills may be preserved longer because they are controlled by parts of the brain affected later in the course of the disease.

When to see a doctor

A number of conditions, including treatable conditions, can result in memory loss or other dementia symptoms. If you are concerned about your memory or other thinking skills, talk to your doctor for a thorough assessment and diagnosis.

If you are concerned about thinking skills you observe in a family member or friend, talk about your concerns and ask about going together to a doctor's appointment.

Causes

The exact causes of Alzheimer's disease aren't fully understood. But at a basic level, brain proteins fail to function normally, which disrupts the work of brain cells (neurons) and triggers a series of toxic events. Neurons are damaged, lose connections to each other and eventually die.

Scientists believe that for most people, Alzheimer's disease is caused by a combination of genetic, lifestyle and environmental factors that affect the brain over time.

Less than 1% of the time, Alzheimer's is caused by specific genetic changes that virtually guarantee a person will develop the disease. These rare occurrences usually result in disease onset in middle age.

The damage most often starts in the region of the brain that controls memory, but the process begins years before the first symptoms. The loss of neurons spreads in a somewhat predictable pattern to other regions of the brains. By the late stage of the disease, the brain has shrunk significantly.

Researchers trying to understand the cause of Alzheimer's disease are focused on the role of two proteins:

Plaques. Beta-amyloid is a fragment of a larger protein. When these fragments cluster together, they appear to have a toxic effect on neurons and to disrupt cell-to-cell communication. These clusters form larger deposits called amyloid plaques, which also include other cellular debris.
Tangles. Tau proteins play a part in a neuron's internal support and transport system to carry nutrients and other essential materials. In Alzheimer's disease, tau proteins change shape and organize themselves into structures called neurofibrillary tangles. The tangles disrupt the transport system and are toxic to cells.

Risk factors

Age

Increasing age is the greatest known risk factor for Alzheimer's disease. Alzheimer's is not a part of normal aging, but as you grow older the likelihood of developing Alzheimer's disease increases.

One study, for example, found that annually there were four new diagnoses per 1,000 people ages 65 to 74, 32 new diagnoses per 1,000 people ages 75 to 84, and 76 new diagnoses per 1,000 people age 85 and older.

Family history and genetics

Your risk of developing Alzheimer's is somewhat higher if a first-degree relative — your parent or sibling — has the disease. Most genetic mechanisms of Alzheimer's among families remain largely unexplained, and the genetic factors are likely complex.

One better understood genetic factor is a form of the apolipoprotein E gene (APOE). A variation of the gene, APOE e4, increases the risk of Alzheimer's disease. Approximately 25% to 30% of the population carries an APOE e4 allele, but not everyone with this variation of the gene develops the disease.

Scientists have identified rare changes (mutations) in three genes that virtually guarantee a person who inherits one of them will develop Alzheimer's. But these mutations account for less than 1% of people with Alzheimer's disease.

Down syndrome

Many people with Down syndrome develop Alzheimer's disease. This is likely related to having three copies of chromosome 21 — and subsequently three copies of the gene for the protein that leads to the creation of beta-amyloid. Signs and symptoms of Alzheimer's tend to appear 10 to 20 years earlier in people with Down syndrome than they do for the general population.

Sex

There appears to be little difference in risk between men and women, but, overall, there are more women with the disease because they generally live longer than men.

Mild cognitive impairment

Mild cognitive impairment (MCI) is a decline in memory or other thinking skills that is greater than normal for a person's age, but the decline doesn't prevent a person from functioning in social or work environments.

People who have MCI have a significant risk of developing dementia. When the primary MCI deficit is memory, the condition is more likely to progress to dementia due to Alzheimer's disease. A diagnosis of MCI encourages a greater focus on healthy lifestyle changes, developing strategies to make up for memory loss and scheduling regular doctor appointments to monitor symptoms.

Head trauma

People who've had a severe head trauma have a greater risk of Alzheimer's disease. Several large studies found that in people age 50 years or older who had a traumatic brain injury (TBI), the risk of dementia and Alzheimer's disease increased. The risk increases in people with more-severe and multiple TBIs. Some studies indicate that the risk may be greatest within the first six months to two years after the TBI.

Air pollution

Studies in animals have indicated that air pollution particulates can speed degeneration of the nervous system. And human studies have found that air pollution exposure — particularly from traffic exhaust and burning wood — is associated with greater dementia risk.

Excessive alcohol consumption

Drinking large amounts of alcohol has long been known to cause brain changes. Several large studies and reviews found that alcohol use disorders were linked to an increased risk of dementia, particularly early-onset dementia.

Poor sleep patterns

Research has shown that poor sleep patterns, such as difficulty falling asleep or staying asleep, are associated with an increased risk of Alzheimer's disease.

Lifestyle and heart health

Research has shown that the same risk factors associated with heart disease may also increase the risk of Alzheimer's disease. These include:

Lack of exercise
Obesity
Smoking or exposure to secondhand smoke
High blood pressure
High cholesterol
Poorly controlled type 2 diabetes

These factors can all be modified. Therefore, changing lifestyle habits can to some degree alter your risk. For example, regular exercise and a healthy low-fat diet rich in fruits and vegetables are associated with a decreased risk of developing Alzheimer's disease.

Lifelong learning and social engagement

Studies have found an association between lifelong involvement in mentally and socially stimulating activities and a reduced risk of Alzheimer's disease. Low education levels — less than a high school education — appear to be a risk factor for Alzheimer's disease.

Complications

Memory and language loss, impaired judgment and other cognitive changes caused by Alzheimer's can complicate treatment for other health conditions. A person with Alzheimer's disease may not be able to:

Communicate that he or she is experiencing pain
Explain symptoms of another illness
Follow a prescribed treatment plan
Explain medication side effects

As Alzheimer's disease progresses to its last stages, brain changes begin to affect physical functions, such as swallowing, balance, and bowel and bladder control. These effects can increase vulnerability to additional health problems such as:

Inhaling food or liquid into the lungs (aspiration)
Flu, pneumonia and other infections
Falls
Fractures
Bedsores
Malnutrition or dehydration
Constipation or diarrhea
Dental problems such as mouth sores or tooth decay

Prevention

Alzheimer's disease is not a preventable condition. However, a number of lifestyle risk factors for Alzheimer's can be modified. Evidence suggests that changes in diet, exercise and habits — steps to reduce the risk of cardiovascular disease — may also lower your risk of developing Alzheimer's disease and other disorders that cause dementia. Heart-healthy lifestyle choices that may reduce the risk of Alzheimer's include the following:

Exercising regularly
Eating a diet of fresh produce, healthy oils and foods low in saturated fat such as a Mediterranean diet
Following treatment guidelines to manage high blood pressure, diabetes and high cholesterol
Asking your doctor for help to quit smoking if you smoke

Studies have shown that preserved thinking skills later in life and a reduced risk of Alzheimer's disease are associated with participating in social events, reading, dancing, playing board games, creating art, playing an instrument, and other activities that require mental and social engagement.

Diagnosis

An important part of diagnosing Alzheimer's disease includes being able to explain your symptoms, as well as perspective from a close family member or friend about symptoms and their impact on daily life. Additionally, a diagnosis of Alzheimer's disease is based on tests your doctor administers to assess memory and thinking skills.

Laboratory and imaging tests can rule out other potential causes or help the doctor better identify the disease causing dementia symptoms.

Traditionally, Alzheimer's disease was only diagnosed with complete certainty after death, when examining the brain with a microscope revealed the characteristic plaques and tangles. Clinicians and researchers are now able to diagnose Alzheimer's disease during life with more certainty. Biomarkers can detect the presence of plaques and tangles, such as specific types of PET scans or measuring amyloid and tau proteins in plasma and cerebral spinal fluid.

Tests

A diagnostic work-up would likely include the following tests:

Physical and neurological exam

Your doctor will perform a physical exam and likely assess overall neurological health by testing the following:

Reflexes
Muscle tone and strength
Ability to get up from a chair and walk across the room
Sense of sight and hearing
Coordination
Balance

Lab tests

Blood tests may help your doctor rule out other potential causes of memory loss and confusion, such as a thyroid disorder or vitamin deficiencies.

Mental status and neuropsychological testing

Your doctor may give you a brief mental status test to assess memory and other thinking skills. Longer forms of neuropsychological testing may provide additional details about mental function compared with people of a similar age and education level. These tests can help establish a diagnosis and serve as a starting point to track the progression of symptoms in the future.

Brain imaging

Images of the brain are now used chiefly to pinpoint visible abnormalities related to conditions other than Alzheimer's disease — such as strokes, trauma or tumors — that may cause cognitive change. New imaging applications — currently used primarily in major medical centers or in clinical trials — may enable doctors to detect specific brain changes caused by Alzheimer's.

Imaging of brain structures include the following:

Magnetic resonance imaging (MRI). MRI uses radio waves and a strong magnetic field to produce detailed images of the brain. While they may show brain shrinkage of brain regions associated with Alzheimer's disease, MRI scans also rule out other conditions. An MRI is generally preferred to a CT scan for the evaluation of dementia.
Computerized tomography (CT). A CT scan, a specialized X-ray technology, produces cross-sectional images (slices) of your brain. It's usually used to rule out tumors, strokes and head injuries.

Imaging of disease processes can be performed with positron emission tomography (PET). During a PET scan, a low-level radioactive tracer is injected into the blood to reveal a particular feature in the brain. PET imaging may include the following:

Fluorodeoxyglucose (FDG) PET scans show areas of the brain in which nutrients are poorly metabolized. Identifying patterns of degeneration — areas of low metabolism — can help distinguish between Alzheimer's disease and other types of dementia.
Amyloid PET imaging can measure the burden of amyloid deposits in the brain. This imaging is primarily used in research but may be used if a person has unusual or very early onset of dementia symptoms.
Tau PET imaging, which measures the burden of neurofibrillary tangles in the brain, is generally used in the research setting.

In special circumstances, such as rapidly progressive dementia, dementia with atypical features or early-onset dementia, other tests may be used to measure abnormal beta-amyloid and tau in the cerebrospinal fluid.

Future diagnostic tests

Researchers are working to develop tests that can measure biological signs of disease processes in the brain.

These tests, including blood tests, may improve the accuracy of diagnoses and enable earlier diagnosis before the onset of symptoms. A blood test for Plasma Aβ is currently available and recently received certification in the U.S. by the Centers for Medicare & Medicaid Services to allow distribution on the market.

Genetic testing generally isn't recommended for a routine Alzheimer's disease evaluation. The exception is people who have a family history of early-onset Alzheimer's disease. Meeting with a genetic counselor to discuss the risks and benefits of genetic testing is recommended before undergoing any tests.

Treatment

Drugs

Current Alzheimer's medications can help for a time with memory symptoms and other cognitive changes. Two types of drugs are currently used to treat cognitive symptoms:

Cholinesterase inhibitors. These drugs work by boosting levels of cell-to-cell communication by preserving a chemical messenger that is depleted in the brain by Alzheimer's disease. These are usually the first medications tried, and most people see modest improvements in symptoms.

Cholinesterase inhibitors may also improve neuropsychiatric symptoms, such as agitation or depression. Commonly prescribed cholinesterase inhibitors include donepezil (Aricept), galantamine (Razadyne ER) and rivastigmine (Exelon).

The main side effects of these drugs include diarrhea, nausea, loss of appetite and sleep disturbances. In people with certain heart disorders, serious side effects may include cardiac arrhythmia.
Memantine (Namenda). This drug works in another brain cell communication network and slows the progression of symptoms with moderate to severe Alzheimer's disease. It's sometimes used in combination with a cholinesterase inhibitor. Relatively rare side effects include dizziness and confusion.

In June 2021, the Food and Drug Administration (FDA) approved aducanumab (Aduhelm) for the treatment of some cases of Alzheimer's disease. This is the first drug approved in the United States to treat the underlying cause of Alzheimer's by targeting and removing amyloid plaques in the brain. The FDA approved the drug on the condition that further studies be conducted to confirm the drug's benefit. Experts also need to identify which patients may benefit from the drug.

Sometimes other medications such as antidepressants may be prescribed to help control the behavioral symptoms associated with Alzheimer's disease.

Creating a safe and supportive environment

Adapting the living situation to the needs of a person with Alzheimer's disease is an important part of any treatment plan. For someone with Alzheimer's, establishing and strengthening routine habits and minimizing memory-demanding tasks can make life much easier.

You can take these steps to support a person's sense of well-being and continued ability to function:

Always keep keys, wallets, mobile phones and other valuables in the same place at home, so they don't become lost.
Keep medications in a secure location. Use a daily checklist to keep track of dosages.
Arrange for finances to be on automatic payment and automatic deposit.
Have the person with Alzheimer's carry a mobile phone with location capability so that a caregiver can track its location. Program important phone numbers into the phone.
Install alarm sensors on doors and windows.
Make sure regular appointments are on the same day at the same time as much as possible.
Use a calendar or whiteboard in the home to track daily schedules. Build the habit of checking off completed items.
Remove excess furniture, clutter and throw rugs.
Install sturdy handrails on stairways and in bathrooms.
Ensure that shoes and slippers are comfortable and provide good traction.
Reduce the number of mirrors. People with Alzheimer's may find images in mirrors confusing or frightening.
Make sure that the person with Alzheimer's carries identification or wears a medical alert bracelet.
Keep photographs and other meaningful objects around the house.

Alternative medicine

Various herbal remedies, vitamins and other supplements are widely promoted as preparations that may support cognitive health or prevent or delay Alzheimer's. Clinical trials have produced mixed results with little evidence to support them as effective treatments.

Some of the treatments that have been studied recently include:

Vitamin E. Although vitamin E doesn't prevent Alzheimer's, taking 2,000 international units daily may help delay the progression in people who already have mild to moderate disease. However, study results have been mixed, with only some showing modest benefits. Further research into the safety of 2,000 international units daily of vitamin E in a dementia population will be needed before it can be routinely recommended.

Supplements promoted for cognitive health can interact with medications you're taking for Alzheimer's disease or other health conditions. Work closely with your health care team to create a safe treatment plan with any prescriptions, over-the-counter medications or dietary supplements.
Omega-3 fatty acids. Omega-3 fatty acids in fish or from supplements may lower the risk of developing dementia, but clinical studies have shown no benefit for treating Alzheimer's disease symptoms.
Curcumin. This herb comes from turmeric and has anti-inflammatory and antioxidant properties that might affect chemical processes in the brain. So far, clinical trials have found no benefit for treating Alzheimer's disease.
Ginkgo. Ginkgo is a plant extract containing several medicinal properties. A large study funded by the National Institutes of Health found no effect in preventing or delaying Alzheimer's disease.
Melatonin. This supplement of a hormone that regulates sleep is being studied to determine if it offers benefits managing sleep in people with dementia. But some research has indicated that melatonin may worsen mood in some people with dementia. More research is needed.

Lifestyle and home remedies

Healthy lifestyle choices promote good overall health and may play a role in maintaining cognitive health.

Exercise

Regular exercise is an important part of a treatment plan. Activities such as a daily walk can help improve mood and maintain the health of joints, muscles and the heart. Exercise can also promote restful sleep and prevent constipation — and it's beneficial for care partners, too.

People with Alzheimer's who develop trouble walking may still be able to use a stationary bike, stretch with elastic bands or participate in chair exercises. You may find exercise programs geared to older adults on TV or on DVDs.

Nutrition

People with Alzheimer's may forget to eat, lose interest in preparing meals or not eat a healthy combination of foods. They may also forget to drink enough, leading to dehydration and constipation.

Offer the following:

Healthy options. Buy favorite healthy food options that are easy to eat.
Water and other healthy beverages. Encourage drinking several glasses of liquids every day. Avoid beverages with caffeine, which can increase restlessness, interfere with sleep and trigger a frequent need to urinate.
High-calorie, healthy shakes and smoothies. Supplement milkshakes with protein powders or make smoothies featuring favorite ingredients, especially when eating becomes more difficult.

Social engagement and activities

Social interactions and activities can support the abilities and skills that are preserved. Doing things that are meaningful and enjoyable are important for the overall well-being of a person with Alzheimer's disease. These might include:

Listening to music or dancing
Reading or listening to books
Gardening or crafts
Social events at senior or memory care centers
Planned activities with children

Coping and support

People with Alzheimer's disease experience a mixture of emotions — confusion, frustration, anger, fear, uncertainty, grief and depression.

If you're caring for someone with Alzheimer's, you can help them cope with the disease by being there to listen, reassuring the person that life can still be enjoyed, providing support, and doing your best to help the person retain dignity and self-respect.

A calm and stable home environment can help reduce behavior problems. New situations, noise, large groups of people, being rushed or pressed to remember, or being asked to do complicated tasks can cause anxiety. As a person with Alzheimer's becomes upset, the ability to think clearly declines even more.

Caring for the caregiver

Caring for a person with Alzheimer's disease is physically and emotionally demanding. Feelings of anger and guilt, stress and discouragement, worry and grief, and social isolation are common.

Caregiving can even take a toll on the caregiver's physical health. Paying attention to your own needs and well-being is one of the most important things you can do for yourself and for the person with Alzheimer's.

If you're a caregiver for someone with Alzheimer's, you can help yourself by:

Learning as much about the disease as you can
Asking questions of doctors, social workers and others involved in the care of your loved one
Calling on friends or other family members for help when you need it
Taking a break every day
Spending time with your friends
Taking care of your health by seeing your own doctors on schedule, eating healthy meals and getting exercise
Joining a support group
Making use of a local adult day center, if possible

Many people with Alzheimer's and their families benefit from counseling or local support services. Contact your local Alzheimer's Association affiliate to connect with support groups, doctors, occupational therapists, resources and referrals, home care agencies, residential care facilities, a telephone help line, and educational seminars.

Preparing for an appointment

Medical care for the loss of memory or other thinking skills usually requires a team or partner strategy. If you're worried about memory loss or related symptoms, ask a close relative or friend to go with you to a doctor's appointment. In addition to providing support, your partner can provide help in answering questions.

If you're going with someone to a doctor's appointment, your role may be to provide some history or your thoughts on changes you have seen. This teamwork is an important part of medical care for initial appointments and throughout a treatment plan.

Your primary care doctor may refer you to a neurologist, psychiatrist, neuropsychologist or other specialist for further evaluation.

What you can do

You can prepare for your appointment by writing down as much information as possible to share. Information may include:

Medical history, including any past or current diagnoses and family medical history
Medical team, including the name and contact information of any current physician, mental health professional or therapist
Medications, including prescriptions, over-the-counter drugs, vitamins, herbal medications or other dietary supplements
Symptoms, including specific examples of changes in memory or thinking skills

What to expect from your doctor

Your doctor will likely ask a number of the following questions to understand changes in memory or other thinking skills. If you are accompanying someone to an appointment, be prepared to provide your perspective as needed. Your doctor may ask:

What kinds of memory difficulties and mental lapses are you having? When did you first notice them?
Are they steadily getting worse, or are they sometimes better and sometimes worse?
Have you stopped doing certain activities, such as managing finances or shopping, because these activities were too mentally challenging?
How is your mood? Do you feel depressed, sadder or more anxious than usual?
Have you gotten lost lately on a driving route or in a situation that's usually familiar to you?
Has anyone expressed unusual concern about your driving?
Have you noticed any changes in the way you tend to react to people or events?
Do you have more energy than usual, less than usual or about the same?
What medications are you taking? Are you taking any vitamins or supplements?
Do you drink alcohol? How much?
Have you noticed any trembling or trouble walking?
Are you having any trouble remembering your medical appointments or when to take your medication?
Have you had your hearing and vision tested recently?
Did anyone else in your family ever have memory trouble? Was anyone ever diagnosed with Alzheimer's disease or dementia?
Do you act out your dreams while sleeping (punch, flail, shout, scream)? Do you snore?