Alzheimer’s Disease: Symptoms, Causes, Stages & Treatment

Alzheimer’s disease is a progressive brain disorder that gradually affects memory, thinking, behavior and a person’s ability to manage everyday life.

It is the most common cause of dementia, particularly in older adults, although Alzheimer’s is not considered a normal part of aging.

The disease develops slowly. Changes in the brain can begin many years before noticeable memory or thinking problems appear. As Alzheimer’s progresses, a person usually needs increasing levels of support and care.

This guide explains Alzheimer’s disease symptoms, causes, risk factors, stages, diagnosis, treatment and caregiving, along with some of the latest developments in Alzheimer’s research and medicine.

What Is Alzheimer’s Disease?

Alzheimer’s disease is a neurodegenerative disease. This means that nerve cells in the brain gradually become damaged, lose their connections with other cells and eventually die.

Two of the best-known changes associated with Alzheimer’s are abnormal accumulations of proteins in the brain:

  • Amyloid plaques, which form between nerve cells.
  • Tau tangles, which develop inside nerve cells.

These changes interfere with communication between brain cells and contribute to progressive loss of brain function.

Brain scan showing changes associated with Alzheimer’s disease

Memory is often affected first because Alzheimer’s commonly begins in areas of the brain involved in forming new memories. However, language, judgment, reasoning, movement and behavior may also become affected as the disease progresses.

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

Alzheimer’s disease and dementia are related, but they are not exactly the same thing.

Dementia is an umbrella term describing a decline in memory, thinking or other cognitive abilities that is severe enough to interfere with daily life.

There are several causes and types of dementia, including:

Alzheimer’s disease is the most common of these.

What Causes Alzheimer’s Disease?

Researchers do not believe that most cases of Alzheimer’s disease have one single cause.

According to the National Institute on Aging, Alzheimer’s probably develops through a complex interaction of age-related brain changes, genetics, lifestyle, cardiovascular health and environmental factors.

Rare genetic mutations can directly cause Alzheimer’s disease in some families. However, these inherited forms account for only a small proportion of cases.

For most people, genetics may increase or decrease risk rather than determine with certainty whether Alzheimer’s will develop.

Alzheimer’s Disease Risk Factors

Researchers have identified several factors associated with an increased risk of developing Alzheimer’s disease.

Age

Increasing age is the strongest known risk factor for Alzheimer’s disease.

Most people diagnosed with Alzheimer’s are aged 65 or older. However, age itself does not cause Alzheimer’s, and dementia is not an inevitable consequence of growing older.

Family History and Genetics

Having a parent or sibling with Alzheimer’s may increase a person’s risk, particularly when several family members have developed the condition.

Genes such as APOE can influence risk, but having a particular genetic variation does not necessarily mean a person will develop Alzheimer’s.

Cardiovascular Health

Conditions that affect the heart and blood vessels may also influence brain health.

These include:

You can read more about the connection between heart disease and dementia.

Head Injury

Some research has found an association between significant traumatic brain injury and an increased risk of dementia later in life.

Down Syndrome

People with Down syndrome have a considerably increased risk of developing Alzheimer’s disease as they grow older.

This is partly because the chromosome involved in Down syndrome contains a gene associated with production of amyloid precursor protein.

We discuss this further in our guide to Down syndrome and Alzheimer’s disease.

Hearing Loss and Other Modifiable Factors

Research increasingly suggests that several potentially modifiable factors may influence dementia risk across a person’s lifetime.

These include hearing loss, physical inactivity, smoking, social isolation and poorly controlled cardiovascular risk factors.

Having one or more risk factors does not mean that someone will develop Alzheimer’s disease.

Symptoms of Alzheimer’s Disease

Alzheimer’s symptoms vary between individuals, and the order in which they appear is not always the same.

Memory problems are common early symptoms. However, changes in language, reasoning, judgment and visual or spatial abilities may also occur.

Possible early warning signs include:

  • Repeatedly forgetting recently learned information
  • Asking the same questions again and again
  • Difficulty planning or solving familiar problems
  • Problems handling money or paying bills
  • Losing track of dates or appointments
  • Becoming lost in familiar locations
  • Difficulty finding the correct words
  • Misplacing objects in unusual places
  • Reduced judgment
  • Changes in mood or personality
  • Withdrawal from familiar activities

Occasionally forgetting a name or appointment is not automatically a sign of Alzheimer’s. The important distinction is whether cognitive changes become persistent and begin interfering with everyday life.

Read more about common signs of memory loss and when they may warrant further assessment.

Stages of Alzheimer’s Disease

Alzheimer’s disease progresses gradually and does not follow exactly the same course in every individual.

Doctors often describe the symptomatic stages as mild, moderate and severe.

Mild Alzheimer’s Disease

During mild Alzheimer’s disease, a person may still live relatively independently but begin experiencing noticeable difficulty with memory and more complicated daily activities.

Changes can include:

  • Forgetting recent conversations or events
  • Repeating questions
  • Difficulty organizing or planning
  • Problems managing finances
  • Difficulty finding words
  • Losing possessions
  • Getting lost
  • Changes in personality, anxiety or irritability

Some people first experience mild cognitive impairment or MCI. People with MCI have measurable cognitive changes but can generally continue performing their usual daily activities independently.

Not everybody with MCI develops Alzheimer’s disease.

Moderate Alzheimer’s Disease

During the moderate stage, memory and thinking problems become more significant and people generally require greater supervision and assistance.

Symptoms may include:

  • Increasing confusion
  • Difficulty recognizing people
  • Problems reading, writing or using numbers
  • Difficulty completing familiar tasks
  • Changes in sleeping patterns
  • Wandering
  • Agitation or anxiety
  • Suspicion or paranoia
  • Delusions or hallucinations in some individuals
  • Difficulty dressing or carrying out personal care

Our guide to middle-stage Alzheimer’s disease looks more closely at this period.

Severe Alzheimer’s Disease

In severe Alzheimer’s disease, a person becomes highly dependent on other people for everyday care.

Symptoms can include:

  • Severe memory loss
  • Limited ability to communicate
  • Difficulty recognizing surroundings
  • Difficulty swallowing
  • Loss of bladder or bowel control
  • Reduced mobility
  • Weight loss
  • Increasing physical frailty

Eventually, many people require around-the-clock care.

Early-Onset and Late-Onset Alzheimer’s Disease

The terms early-onset and late-onset describe the age when Alzheimer’s symptoms begin. They should not be confused with the mild, moderate and severe stages of the disease.

Most people develop symptoms after age 65. This is generally known as late-onset Alzheimer’s disease.

When Alzheimer’s develops before age 65, it is called younger-onset or early-onset Alzheimer’s disease.

Learn more in our guide to the signs of early-onset Alzheimer’s.

How Is Alzheimer’s Disease Diagnosed?

There is no single routine test that doctors use by itself to diagnose every case of Alzheimer’s disease.

Instead, doctors consider several sources of information.

Doctor discussing memory concerns and treatment options with an older patient and family member

Medical History

A doctor may ask about:

  • When memory or thinking problems began
  • Whether symptoms are getting worse
  • Medical history
  • Family history
  • Medications
  • Alcohol use
  • Sleep
  • Mood and mental health
  • Ability to perform everyday tasks

Information from a spouse, family member or close friend may also be helpful.

Cognitive Testing

Doctors may use cognitive tests to examine memory, attention, language, reasoning and problem-solving ability.

Physical and Neurological Examination

A physical examination can help identify health problems that may contribute to cognitive symptoms.

Doctors may also examine reflexes, coordination, balance, muscle strength and sensory function.

Laboratory Tests

Blood and other laboratory tests can help identify conditions that may cause or worsen memory problems.

Examples include thyroid disorders, vitamin deficiencies, infections and metabolic problems.

Brain Imaging

Brain imaging may include:

  • MRI to examine brain structure and identify conditions such as strokes or tumors.
  • CT scans in situations where structural imaging is required.
  • PET imaging, including specialized scans that can detect abnormal amyloid or tau proteins in appropriate patients.

Read more about whether an MRI can detect dementia.

Biomarker Tests

Advances in Alzheimer’s diagnosis mean doctors can increasingly use biological markers associated with the disease.

Cerebrospinal fluid obtained through a lumbar puncture can be tested for proteins related to Alzheimer’s disease.

Blood-based biomarker testing is also developing rapidly. In 2025, the U.S. Food and Drug Administration cleared the first blood test designed to help detect amyloid pathology associated with Alzheimer’s disease in certain symptomatic adults.

Blood tests are used as part of a broader clinical assessment rather than as a stand-alone dementia diagnosis.

Why Early Diagnosis Matters

Obtaining a diagnosis early can give a person and their family valuable time to understand the condition and make plans.

An early assessment may also identify another medical problem causing dementia-like symptoms.

Other potential advantages include:

  • Starting appropriate treatment earlier
  • Discussing newly available treatment options
  • Participating in clinical trials
  • Planning financial and legal affairs
  • Discussing future care preferences
  • Making home and lifestyle adjustments
  • Accessing caregiver and community support

Alzheimer’s Disease Treatment

There is currently no cure that completely stops or reverses Alzheimer’s disease.

However, treatment has changed considerably in recent years.

Some medications treat symptoms, while newer disease-modifying therapies can slow progression in selected people who are in the early stages of Alzheimer’s disease.

Disease-Modifying Alzheimer’s Treatments

Newer anti-amyloid treatments target amyloid protein in the brain.

FDA-approved treatments include:

These medications are intended for appropriately selected people with mild cognitive impairment or mild dementia due to Alzheimer’s disease and evidence of amyloid pathology.

They are not cures. Clinical trials found that they can slow cognitive and functional decline in some patients rather than restore abilities that have already been lost.

Anti-amyloid treatments can also cause potentially serious side effects, including amyloid-related imaging abnormalities known as ARIA. The FDA has issued specific MRI monitoring recommendations for people taking Leqembi because ARIA can involve swelling or bleeding in the brain.

For this reason, treatment requires careful medical assessment, discussion of risks and benefits, and appropriate monitoring.

Medicines for Cognitive Symptoms

Several medications have been used for many years to help manage cognitive symptoms of Alzheimer’s disease.

Cholinesterase inhibitors include:

  • Donepezil
  • Rivastigmine
  • Galantamine

These medications may help some people with memory, thinking or daily functioning for a period of time.

Memantine works differently and may be prescribed for moderate to severe Alzheimer’s disease.

Doctors sometimes use combinations of these medications depending on the individual.

Treating Behavioral and Psychological Symptoms

Alzheimer’s can also cause anxiety, depression, agitation, sleep problems, hallucinations and other behavioral changes.

Doctors usually look first for possible triggers such as:

  • Pain
  • Infection
  • Medication side effects
  • Hunger or thirst
  • Constipation
  • Overstimulation
  • Changes in routine
  • Unfamiliar surroundings

Environmental and behavioral approaches are often useful.

Medication may sometimes be considered when symptoms are severe, but this requires careful medical supervision because some medicines carry important risks for older adults with dementia.

Non-Drug Approaches to Alzheimer’s Care

Daily routines, meaningful activities and a supportive environment can have an important role in Alzheimer’s care.

Helpful approaches may include:

Other supportive approaches may include occupational therapy and reminiscence therapy, depending on the person’s needs and preferences.

Some complementary therapies may improve comfort or enjoyment for certain people, but they should not be presented as cures for Alzheimer’s disease.

Herbal remedies and supplements can also interact with prescription medicines. Anyone considering them should discuss their use with a qualified healthcare professional.

Can Alzheimer’s Disease Be Prevented?

There is currently no guaranteed way to prevent Alzheimer’s disease.

However, growing evidence suggests that protecting overall cardiovascular and brain health may reduce the risk of cognitive decline and dementia.

Potentially helpful steps include:

  • Remaining physically active
  • Managing high blood pressure
  • Managing diabetes and cholesterol
  • Not smoking
  • Eating a nutritious diet
  • Treating hearing loss
  • Staying socially connected
  • Keeping mentally active
  • Getting adequate sleep
  • Avoiding excessive alcohol
  • Reducing the risk of serious head injuries

These actions cannot guarantee that Alzheimer’s will be prevented, but many also have important benefits for heart and general health.

See our guide to ways to reduce the risk of dementia.

Complications of Alzheimer’s Disease

As Alzheimer’s progresses, cognitive and physical changes can contribute to additional health problems.

Possible complications include:

Difficulty communicating can also make it harder for a person to explain that they are in pain or feeling unwell.

Life Expectancy With Alzheimer’s Disease

Alzheimer’s disease progresses differently in every person.

Age at diagnosis, other medical conditions and the stage of disease can all affect survival.

Some people live for many years after diagnosis, while others decline more rapidly.

In later stages, complications such as pneumonia, swallowing problems and infections often become significant health concerns.

Alzheimer’s Caregiving

Caring for someone with Alzheimer’s disease can become increasingly demanding as the illness progresses.

Caregiving responsibilities may include:

  • Helping with medications
  • Preparing meals
  • Providing transportation
  • Managing appointments
  • Helping with bathing, dressing and grooming
  • Making the home safer
  • Providing emotional support
  • Managing behavioral changes
  • Helping organize financial and legal matters
  • Planning for future care

Whenever possible, important decisions should be discussed while the person with Alzheimer’s can still participate meaningfully in them.

Clear and supportive communication can also make everyday care easier as cognitive changes progress.

Caregivers also need support themselves. Respite care, family assistance, caregiver groups and professional services can become important as care needs increase.

You may find our dementia care resources useful when planning support.

For more topics covering symptoms, care and related conditions, browse the Dementia Resource Library.

Alzheimer’s Disease Statistics

Alzheimer’s disease affects millions of families across the United States.

According to the Alzheimer’s Association 2026 Alzheimer’s Disease Facts and Figures:

  • Approximately 7.4 million Americans aged 65 and older are living with Alzheimer’s dementia.
  • About 1 in 9 Americans aged 65 and older has Alzheimer’s.
  • Almost two-thirds of Americans living with Alzheimer’s are women.

The number of people affected is expected to increase as the population grows older.

When Should You Speak to a Doctor?

Memory changes do not automatically mean someone has Alzheimer’s disease.

Many other conditions can affect memory and thinking, including depression, sleep disorders, medication effects, vitamin deficiencies, thyroid problems, infections and other neurological conditions.

However, persistent changes should not simply be dismissed as aging.

Consider speaking with a doctor when memory or thinking problems:

  • Are becoming progressively worse
  • Interfere with work or household activities
  • Affect finances or medication management
  • Cause someone to become lost
  • Lead to significant changes in judgment
  • Are noticed repeatedly by friends or relatives

Early medical assessment can help determine what is causing the symptoms and what support or treatment may be appropriate.

Alzheimer’s Disease: Final Thoughts

Alzheimer’s disease is a complex and progressive brain disorder, but our understanding of it continues to improve.

There is still no cure. However, advances in brain imaging, biomarkers, blood testing and disease-modifying treatments are changing the way Alzheimer’s can be diagnosed and treated.

For people living with the disease, good medical care, appropriate treatment, a supportive environment and thoughtful caregiving can help maintain independence and quality of life for as long as possible.

If you are concerned about changes in your own memory or the memory and thinking abilities of someone close to you, speak with a qualified healthcare professional for an individual assessment.