Lewy body dementia

Lewy body dementia (LBD) is one of the most common kinds of dementia after Alzheimer's disease and vascular dementia.¹ About 1.4 million people in the United States are thought to live with it.⁴ It often starts after age 50, and it affects slightly more men than women.¹

LBD can look very different from day to day. A person may be clear in the morning and confused by afternoon. Knowing the signs matters, because the right diagnosis can protect your loved one from medicines that may cause serious harm.

What happens in the brain

In LBD, a protein called alpha-synuclein (a protein that normally helps nerve cells send signals) folds the wrong way. It forms clumps inside brain cells. These clumps are called Lewy bodies.²

Lewy bodies upset two important brain chemicals. One is acetylcholine, which helps with memory and learning. The other is dopamine, which helps with movement, mood and sleep.² That is why LBD affects thinking, movement and sleep.

LBD has two forms. In dementia with Lewy bodies (DLB), thinking problems come first, or within a year of movement problems. In Parkinson's disease dementia, movement problems of Parkinson's come first, and thinking problems start more than a year later.^2,6 Doctors call this the "one-year rule." See Parkinson's disease dementia.

The main signs

Doctors look for four core signs, along with a decline in thinking that gets in the way of daily life.^5,6

1. Swings in alertness and attention

This is often called fluctuation. The person may seem nearly normal one hour, then be very drowsy, confused or staring into space the next.⁶ These swings can look like delirium (sudden confusion from illness).⁶ They come from the disease, not from lack of effort.

2. Seeing things that are not there

Visual hallucinations happen in most people with LBD, and they often start early.¹ The visions usually look detailed and real, such as children or animals.¹ See our page on hallucinations and delusions.

3. Acting out dreams (REM sleep behavior disorder)

During dream sleep, the body normally stays still. In REM sleep behavior disorder, the person talks, shouts, punches or kicks while dreaming.¹ It can show up years before memory changes.¹

4. Parkinson-like movement (parkinsonism)

This means slow movement, stiff muscles, a shaking hand at rest, or a shuffling walk.⁶ Balance problems and falls are common.¹

Other signs families notice

• Trouble with attention, solving problems and judging distance. Memory loss may be milder at first than in Alzheimer's disease.^1,6
• Dizziness or fainting when standing up, because blood pressure drops.¹
• Constipation, bladder problems and trouble with body temperature.¹
• Loss of smell, and being very sleepy during the day.^2,5
• Depression, anxiety, apathy (loss of interest), or false beliefs such as paranoia.¹

How doctors diagnose LBD

No single test proves LBD while a person is alive. Only a brain exam after death can confirm it.¹ Doctors put the picture together from the history, an exam and some tests.²

LBD is often missed. Early on, it can look like Alzheimer's disease or a mental illness.^1,8 Bring a written list of symptoms, and describe the bad days, not only the good ones. The LBDA's free symptoms checklist can help.¹⁵

The diagnosis criteria in plain words

Doctors use criteria written by an international group of experts and published in 2017.⁵ In simple terms:

• The person must have dementia, meaning thinking problems serious enough to affect daily life.
• Probable DLB means dementia plus at least two of the four core signs above. It can also mean dementia plus one core sign plus a positive result on a special test.⁵
• The special tests that count are a brain scan showing low dopamine transporter levels (such as a DaT scan), a heart nerve scan called MIBG, or a sleep study that confirms REM sleep behavior disorder.⁵
• Possible DLB means dementia plus one core sign but no positive test, or a positive test but no core signs.⁵ Doctors then keep watching over time.

Blood tests, memory tests, and an MRI or CT scan help rule out other causes.² Learn more about memory and thinking tests and brain scans.

DaT scan

A DaT scan (DaTscan) looks at dopamine transporters, which are parts of the nerve cells that use dopamine. In LBD and Parkinson's, the scan often shows fewer of them.^5,7

The FDA expanded its approval of DaTscan in late 2022 to include people with suspected dementia with Lewy bodies.⁸ The scan uses a small amount of a radioactive tracer given in a vein. Before the shot, the person takes a medicine to protect the thyroid. The pictures are taken 3 to 6 hours later with a SPECT camera.⁷

In a small study of people thought to have DLB or Alzheimer's, scan results were checked against brain exams after death. The scan correctly found about 4 in 5 people who had DLB. It correctly ruled out DLB in about 9 in 10 people who did not have it.⁷ A normal scan alone does not rule out LBD.¹² Some medicines can affect the result, so share a full medicine list.⁷ The scan adds to a doctor's exam; it does not replace it.⁷

Skin biopsy test for alpha-synuclein

A newer test looks for the abnormal alpha-synuclein protein in the skin. The doctor numbs small spots and takes three tiny skin samples, each about 3 millimeters wide (smaller than a pencil eraser). In the main U.S. study, they came from the neck, knee and ankle.¹⁰

In a large U.S. study published in 2024, the protein was found in 96 out of 100 people with DLB. It was found in only about 3 out of 100 healthy people.¹⁰ A 2026 follow-up of people referred with suspected DLB again found it in 96% of those who met the criteria.⁹ But it was also found in about 1 in 3 people in the comparison group who had low scores on a thinking test but no signs of Lewy disease.⁹

What this means for you:

• A positive skin test shows Lewy-type protein in the body. It cannot tell DLB apart from Parkinson's disease or related conditions on its own.¹⁰
• Skin tests and spinal fluid tests for alpha-synuclein are not yet part of the official 2017 criteria.⁵ Experts call them emerging tools.¹¹
• Ask your neurologist whether the test makes sense for your situation, and whether your insurance or Medicare plan will pay for it.

Treatment

There is no cure for LBD, and no medicine can stop the disease from getting worse.⁶ As of October 2026, no medicine is FDA-approved for dementia with Lewy bodies. Rivastigmine is approved for thinking problems in Parkinson's disease dementia.^1,13 Doctors use other medicines "off-label," meaning for a use the FDA has not formally approved.¹³

Medicines to avoid or question

Some other medicines can also make LBD worse. Talk with the doctor or pharmacist before changing anything.

• Anticholinergic medicines, which block acetylcholine. These include diphenhydramine (Benadryl) and many store-bought sleep aids and bladder pills.¹³ See medicines that can worsen memory.
• Sleeping pills and benzodiazepines, such as zolpidem (Ambien) or lorazepam. The exception is clonazepam when a doctor prescribes it for dream-acting sleep.¹³
• Strong pain medicines, such as opioids and tramadol, which can cause confusion.^1,13
• Anesthesia for surgery, which can bring on delirium. Make sure the surgeon and anesthesia team know about LBD ahead of time.^1,13
• Herbal products and supplements, including herbal medicines from any tradition. Bring every bottle to the doctor so they can check for problems.

Caregiving tips

These steps can help with the daily ups and downs of LBD.

1. Carry the wallet card. Print the free LBDA Medical Alert Wallet Card. Keep copies in both your wallets, and show it at every ER visit, hospital stay and new doctor.¹⁴
2. Respond to hallucinations with calm. Do not argue about what is real. Speak to the feeling, such as "That sounds scary. I'm here." If the vision does not upset the person, it may not need treatment.^3,13 Simple changes to the room may help.³
3. Plan around good and bad times. Note when the person is most alert, and plan visits, baths and outings for those hours. Our behavior diary can help.
4. Prevent falls. Clear paths, add night lights and grab bars, and ask about physical therapy. Help the person stand up slowly to avoid dizziness.¹³ See preventing falls.
5. Make the bed safer at night. If the person acts out dreams, move sharp or hard furniture away from the bed. A lower bed, floor padding, or sleeping apart for a while can protect you both.
6. Keep days simple. A steady routine, calm rooms and regular exercise help. Avoid crowds and noisy places. Limit long naps and late caffeine.³
7. Watch for sudden changes. A sharp drop in thinking can mean an infection, pain, constipation or a medicine problem.^13,14 Call the doctor. Call 911 for trouble breathing, a bad fall, or a person you cannot wake.
8. Plan ahead early. LBD can change quickly. Talk about health care wishes and legal papers while the person can still take part.³ See advance directives.
9. Care for yourself, too. Watch for signs of burnout, like irritability or poor sleep. Accept help and use respite care or adult day care.³ See caregiver stress.

How LBD changes over time

LBD gets worse over time, but the pace is different for each person. On average, people live about 5 to 7 years after diagnosis. The range is wide, from 2 to 20 years, depending on age, overall health and symptoms.¹ Some symptoms respond to treatment for a while.¹ See stages of dementia and hospice care.

Lewy Body Dementia Association resources

• Lewy Line: call 800-539-9767 for information and support.¹⁵
• Local support groups for care partners, listed on the LBDA website.¹⁵
• Medical Alert Wallet Card, free to download or order in print.¹⁴
• Comprehensive Symptoms Checklist to track symptoms and share with doctors.¹⁵
• Booklets such as Facing LBD Together for newly diagnosed families.¹⁵
• Research Centers of Excellence, a network of more than 27 U.S. academic centers with LBD experts.¹⁵
• Lewy Trial Tracker, a list of studies that are looking for volunteers.¹⁵ See also joining a dementia clinical trial.

When to get help

• See a doctor if someone acts out dreams, sees things that are not there, or has new thinking problems with stiffness or falls. Ask whether LBD could be the cause. See which specialist to see.
• Call the doctor soon if symptoms suddenly get worse, especially after a new medicine.
• Call 911 for signs of a severe medicine reaction (high fever, rigid muscles, can't swallow, can't be woken), a bad fall, or danger to anyone's safety.
• Call or text 988 if you, as a caregiver, feel hopeless or have thoughts of harming yourself. Help is there day and night.

Education only. This page is general information written from the sources listed. It is not medical, legal or financial advice and does not replace a doctor, therapist or lawyer who knows your situation. How we write and check pages.