What is Alzheimer's disease?
Alzheimer's disease is a brain disease that slowly destroys memory, thinking skills, and eventually the ability to carry out simple daily tasks. It is the most common cause of dementia — accounting for 60 to 80 percent of all dementia cases — and it affects more than 7 million Americans today.
The disease is caused by abnormal buildups of two proteins in the brain: amyloid plaques (clumps that form between nerve cells) and tau tangles (twisted fibers that form inside dying cells). These buildups disrupt communication between brain cells and eventually cause those cells to die. Damage typically starts in memory regions and spreads over time.
Alzheimer's is progressive — it gets worse over time. The rate varies: some people live with the disease for a few years, others for 20 years or more. There is currently no cure, but meaningful treatments now exist that can slow its progression, especially when caught early.
Alzheimer's disease is not a normal part of aging. While risk increases with age, many people live well into their 90s with sharp memory and thinking. Memory concerns should always be discussed with a doctor.
10 warning signs to watch for
These warning signs were developed by the Alzheimer's Association. Noticing one or more of them in a loved one is a reason to speak with a doctor — not a definitive diagnosis. Each sign comes with a note on what's typical aging versus what warrants attention.
Forgetting recently learned information, important dates, or asking the same question repeatedly. Relying heavily on reminders for things previously handled independently.
Trouble following a familiar recipe, tracking monthly bills, or concentrating on detail-oriented tasks. Things that used to come naturally now take much longer.
Losing track of dates, seasons, or the passage of time. Forgetting where they are or how they got there. Difficulty understanding events not happening right now.
Difficulty driving to a familiar location, managing a work project, or remembering the rules of a favorite game they've played for decades.
Stopping mid-sentence with no idea how to continue. Struggling to find the right word or calling things by the wrong name. Difficulty following a conversation.
Putting things in unusual places — keys in the freezer, glasses in the microwave. Unable to go back through their steps to find them. May accuse others of stealing.
Unusual financial decisions — giving away large sums. Paying less attention to grooming. Falling for phone scams more easily than before.
Pulling back from hobbies, sports, work projects, or social events. Avoiding situations they once loved because of the changes they've noticed in themselves.
Becoming confused, suspicious, depressed, fearful, or anxious. Easily upset in situations outside their comfort zone. Seeming uncharacteristically unlike themselves.
Difficulty reading, judging distance, or determining color and contrast. May not recognize themselves in a mirror. Can affect the ability to drive safely.
If you recognize several of these signs in a loved one, schedule a doctor's appointment promptly — don't wait for the next annual visit. Early diagnosis opens access to treatments most effective in the early stages, and gives families more time to plan.
Our Disease Guides hub includes a full side-by-side comparison of Alzheimer's, Parkinson's, and Lewy Body Dementia — including how to tell them apart and how they overlap. View the full comparison →
The three stages of Alzheimer's
Alzheimer's progresses through stages — though the timeline looks different for every person. Understanding the stages helps families plan ahead, access the right care at the right time, and know what to expect.
In the early stage, a person may seem mostly like themselves. Changes are subtle and may be dismissed as normal aging. This is the most important time to seek a diagnosis — new disease-modifying treatments are only approved for early-stage Alzheimer's, and the person can still participate in their own care planning.
- Forgetting words or names of familiar people
- Losing or misplacing objects more frequently
- Increasing difficulty with planning or organization
- Trouble remembering recently learned information
- Taking longer than usual to complete familiar tasks
- Some withdrawal from social activities
The middle stage is usually the longest and most demanding for caregivers. Damage has spread in the brain, and the person will need more day-to-day support. It is important to start planning for long-term care arrangements and to actively use caregiver support resources.
- Increasing memory loss and confusion about recent events
- Difficulty recognizing family members and close friends
- Needing help with daily activities — dressing, bathing, meals
- Changes in sleep patterns, often sleeping during the day
- Wandering and risk of getting lost
- Personality shifts including suspicion, agitation, or depression
- Bowel and bladder control issues may begin
In the late stage, Alzheimer's has affected much of the brain. The focus of care shifts toward comfort, dignity, and quality of life. Hospice care is often appropriate and can provide meaningful support for both the person and the family.
- Loss of ability to communicate verbally
- Full dependence on caregivers for all daily needs
- High vulnerability to infections, especially pneumonia
- Loss of ability to walk, sit up independently, or swallow
- Requires full-time, around-the-clock care
What causes Alzheimer's?
Scientists believe Alzheimer's is caused by a combination of genetic, lifestyle, and environmental factors that affect the brain over time. There is no single cause — rather, it involves a complex chain of events starting in the brain, sometimes decades before symptoms appear.
The hallmarks of Alzheimer's in the brain are abnormal deposits of amyloid-beta, which clumps between nerve cells to form plaques, and tau, which accumulates inside nerve cells and forms tangled fibers. These buildups interrupt neuron communication, trigger inflammation, and eventually kill brain cells.
These cannot be changed, but knowing them helps with monitoring and early detection.
- Age — the greatest risk factor. Risk doubles every five years after age 65.
- Family history — having a parent or sibling with Alzheimer's increases risk.
- APOE-e4 gene — a common genetic variant that raises risk. Genetic testing is available.
- Down syndrome — people with Down syndrome have a higher risk in midlife.
- Rare gene mutations — mutations in APP, PSEN1, or PSEN2 cause early-onset Alzheimer's before age 65.
These can be addressed through lifestyle changes and may help reduce risk over time.
- Heart health — high blood pressure, diabetes, and high cholesterol all increase risk.
- Physical inactivity — regular exercise is strongly associated with reduced risk.
- Poor sleep — chronic poor sleep may allow amyloid to accumulate in the brain.
- Social isolation — staying socially and mentally engaged appears protective.
- Smoking — increases vascular disease risk, which contributes to cognitive decline.
- Head trauma — a history of serious head injuries raises Alzheimer's risk.
How is Alzheimer's diagnosed?
There is no single test for Alzheimer's disease. Diagnosis involves a series of evaluations that help a doctor rule out other causes of memory loss — many of which are treatable — and assess the pattern of cognitive decline. Early diagnosis matters: it opens access to treatments most effective in the early stages and gives families more time to plan.
Begin with your loved one's primary care physician. They can conduct initial assessments and refer to a neurologist or memory specialist if needed. Don't wait for the next annual visit — request an appointment specifically to discuss your concerns.
The doctor will ask about current and past health conditions, medications, family history of memory problems, and the specific changes the person and their family have been noticing.
Standardized tests assess memory, problem-solving, attention, and language skills. The most common are the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA). These take about 10–15 minutes in the doctor's office.
Blood tests rule out treatable conditions that can cause similar symptoms — thyroid problems, vitamin deficiencies, and infections. A physical exam evaluates overall health and neurological signs.
MRI or CT scans can reveal brain changes associated with Alzheimer's and rule out other causes like stroke or brain tumors. PET scans can detect amyloid plaques directly and are increasingly used for early diagnosis.
A major recent advance — blood tests can now detect amyloid and tau proteins in the bloodstream, offering an easier, less invasive path to early detection. These are increasingly available and covered by insurance for appropriate patients.
What treatments exist today?
There is no cure for Alzheimer's disease, but the treatment landscape has changed dramatically in recent years. For the first time, drugs now exist that address the underlying biology of the disease — not just the symptoms. Here is a plain-language overview of what is currently available.
A breakthrough in Alzheimer's treatment. These antibody drugs target and clear amyloid plaques from the brain, actually addressing the disease's underlying biology. FDA-approved for early-stage Alzheimer's and mild cognitive impairment. They slow the rate of cognitive decline but do not stop or reverse the disease. Require regular infusions and MRI monitoring for side effects.
These drugs boost acetylcholine, a brain chemical important for memory and thinking. They help manage cognitive symptoms in mild to moderate stages. They don't slow the underlying disease but can meaningfully improve quality of daily life.
Approved for moderate to severe Alzheimer's. Regulates glutamate activity in the brain to help with daily function. Often combined with cholinesterase inhibitors. Generally well tolerated with mild side effects.
In 2026, the FDA approved the first non-antipsychotic medication specifically for agitation in Alzheimer's dementia — addressing one of the disease's most difficult behavioral symptoms with a better safety profile than older options.
Strong evidence supports non-drug approaches that improve quality of life and may help slow progression. These complement medication and are appropriate at any stage of the disease.
Dozens of Alzheimer's clinical trials are actively enrolling. Participating can give access to cutting-edge treatments not yet publicly available. Ask your doctor, or visit clinicaltrials.gov to search for trials near you.
A note on caregiving
Caring for someone with Alzheimer's is one of the most demanding roles a person can take on — and one of the most profound acts of love. Nearly 12 million Americans are doing this work right now, most while holding down jobs, raising children, and managing their own health.
Caregiver burnout is real and common. The most important thing a caregiver can do for their loved one is to take care of themselves too. That means accepting help, building a support network, and knowing when to ask for more.
Create routines. Predictable daily schedules reduce confusion and anxiety. Morning and evening routines especially help.
Simplify communication. Speak slowly, use simple sentences, make eye contact, give only one instruction at a time. Avoid arguing or correcting — it rarely helps and causes distress.
Prepare the home early. Remove tripping hazards, secure medications, lock cabinets with cleaning products. Consider a door alarm if wandering becomes a concern.
Plan legally and financially while you can. Power of attorney, healthcare directives, and financial planning are much easier when the person can still participate. Don't wait for a crisis.