What Is Lewy Body Dementia?

Medically reviewed by Karen Foster, LPC
Updated June 4, 2024by BetterHelp Editorial Team

Several degenerative brain diseases affect cognitive function in people of all ages. One such type of dementia is diffuse Lewy body dementia, which can impact millions of people worldwide. Understanding this condition and its symptoms may prepare you if you or someone you love is experiencing symptoms.

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Definition of diffuse Lewy body dementia

Diffuse Lewy body dementia is the second most common type of degenerative dementia, affecting over 1 million people and their families in the US annually, according to the National Institutes of Health. Some people may have never heard of the condition, and some doctors may be unfamiliar with how it is diagnosed and treated. However, education can be essential to early detection and diagnosis. 

Diffuse Lewy body dementia is a brain disorder that progressively worsens. It's characterized by Lewy body deposits—clusters of the protein alpha-synuclein—in brain regions that control thought, behavior, and movement. These deposits damage brain cells, leading to behavioral symptoms, cognitive impairment, and movement symptoms. Diffuse Lewy body dementia also affects the autonomic nervous system, causing challenges with blood pressure, temperature management, and bladder and bowel incontinence. Lewy body dementia (LBD) can describe one of two disorders: Parkinson’s disease dementia or dementia with Lewy bodies. 

What’s the origin of the name?

Over 100 years ago, in 1912, Fritz Heinrich Lewy studied the brains of people with Parkinson's disease. He found that there were bodies of protein in the nerve cells of the brain's basal ganglia. The basal ganglia are structures in the base of the brain that are involved in movement and coordination.

Although Lewy noticed these bodies, he didn't know that it was characteristic of a specific type of disease. Nevertheless, his contribution to the science of dementia was significant enough that Lewy bodies and Lewy body dementia were named after him.

What is a Lewy body?

Lewy bodies are abnormal formations of protein. They develop inside nerve cells and contribute to Parkinson's disease with or without dementia and Lewy body dementia. They look like a spherical mass and have a dense core and a radiating halo.

What does “diffuse” mean in LBD?

If a stimulus is diffuse, it is spread out and not concentrated. The reason the word "diffuse" is used as a part of the name of diffuse Lewy body dementia is that it indicates that the Lewy bodies have spread out over extended areas of the brain.

How Lewy bodies affect the brain

Lewy bodies impact the way the brain works. They can cause multiple problems with brain functioning that go beyond the potential forgetfulness of old age. Below are some of the impacts. 

REM sleep behavior disorder

REM sleep behavior disorder (RBD) is a common feature of diffuse Lewy body dementia. In RBD, the person has vivid dreams that they act out while they sleep. They may dream they are being chased, so they run in their sleep. They may dream they are being attacked and fight back physically.

Many people's bodies are relaxed or paralyzed during REM sleep. The nervous system doesn't complete this job for people with LBD, so the muscles remain tense as if they were awake. Their dreams may be frightening, and they may act them out because of the RBD.

Severe neuroleptic sensitivity

Doctors can treat hallucinations, delusions, or other behavioral disturbances in most dementias with neuroleptic medications such as haloperidol. However, 50% of people with Lewy body dementia are susceptible to these medications. They have severe reactions that can lead to faster cognitive decline, parkinsonism, drowsiness, neuroleptic malignant syndrome (NMS), or death. Neuroleptic malignant syndrome is a life-threatening reaction to neuroleptics that can cause fever, rigidity in the muscles, and changes in mental state.

Reduced dopamine transporter activity

Dopamine transporters are proteins that manage dopamine reuptake to end a dopamine transmission. People with diffuse Lewy body dementia have decreased dopamine transporter activity in their brains. Scientists can measure the level of this activity. The effects are changes that cause Parkinsonism symptoms.

Risk factors for LBD

Scientists know little about the risk factors for diffuse Lewy body dementia. What is certain is that LBD is more common in males, people over 60, and those who have a history of it in their families. Additionally, Parkinson’s disease can increase the risk that Lewy body dementia will develop. Researchers have identified a few environmental risk factors, including exposure to some metals and air pollution. 

If you believe you’re living with dementia or a related concern, a specialist in neurodegenerative or movement disorders can provide you with screenings and determine whether further testing, a diagnosis, and treatment are necessary.


Symptoms of diffuse Lewy body dementia

Diffuse Lewy body dementia can have many different symptoms. Early on, you may notice symptoms like:

  • Changes in reasoning

  • Confusion or alertness at different times

  • Hunched posture

  • Balance difficulties, including frequent falls 

  • Changes in handwriting

  • Weak voice

  • Loss of smell

  • Misidentifying objects in low light

  • REM sleep disorder

  • Shuffling gait

The most common symptoms include changes in cognition, movement, and sleep, as well as behavioral symptoms. Early stages of Lewy body dementia can sometimes be confused with psychiatric disorders that have similar symptoms. Below is more information about the challenging symptoms that may occur with diffuse Lewy body dementia. 

Memory and cognitive symptoms

Memory problems may be the first clue that you or a loved one has some form of dementia. Lewy body dementia affects the hippocampus, which helps facilitate memory creation, according to the National Institute of Neurological Disorders and Stroke (part of the National Institutes of Health). People with diffuse Lewy body dementia can be forgetful. They can also have trouble with problem-solving and analytical thinking. It may be difficult for them to plan or follow a plan step-by-step. They may be alert and attentive at one time of day and confused or lacking in concentration at another time.

People with LBD may have difficulty interacting in conversations or could start to speak in a disorganized way. Spatial relationships may be complicated to assess, and they may lose their sense of direction. They may become confused. 

Psychiatric symptoms

People with diffuse LBD may have visual or auditory hallucinations or hallucinations related to other senses, such as touch. They may have depression, become apathetic, and have delusions or false beliefs. They may also struggle with anxiety. Visual hallucinations can be distinctive symptoms that indicate a patient has Lewy body dementia (LBD) rather than another type of dementia, such as Alzheimer’s disease. According to the National Institutes of Health, approximately 80% of individuals with LBD experience visual hallucinations.  

Parkinsonian symptoms

Parkinsonian, or Parkinson's-like symptoms, are common in diffuse Lewy body dementia, as Parkinson’s disease and Lewy body dementia are caused by the same underlying changes in the brain. This group of significant movement problems includes muscle rigidity, shuffling gait, balance problems, tremors, moving slowly, weak voice, changes in handwriting, changes in facial expressions, drooling, loss of sense of smell, and changes in posture.

Sleep problems

In addition to acting out dreams due to RBD, people with diffuse Lewy body dementia may have other sleep-related struggles. Changes in sleep behavior can include falling out of bed often, becoming highly sleepy during the day, experiencing insomnia, or developing restless leg syndrome (RLS). Symptoms like restless leg syndrome can make other symptoms worse if the patient doesn’t get enough sleep.

Autonomic system dysfunction

Because diffuse Lewy body dementia affects the autonomic nervous system, it can cause problems in physical functioning. People with LBD may get lightheaded, lose consciousness, have unexplained blackouts, or become increasingly sensitive to heat and cold. They may also have trouble with sexual dysfunction or urinary incontinence, and constipation is common. 

Unpredictability in severity of symptoms

One sign of diffuse Lewy body dementia is that your condition can change dramatically throughout your days. You may not know when you will have a positive or negative day. You may get better or worse from morning to evening. You could experience significant movement problems over the weekend but then regain full mobility on Monday. Unpredictability can bring false hope or despair. The fluctuations in functioning from day to day are other distinctive symptoms that distinguish Lewy body dementia from other neurological disorders. 

What to expect with Lewy body dementia

It can be challenging to know what to expect with diffuse Lewy body dementia daily and in the long term. The condition is a progressive disease, meaning symptoms start slowly and become worse over time. Some people can live with Lewy body dementia for up to 20 years. Others don't survive for two years. The average time people live with LBD is five to seven years after diagnosis.

With an early diagnosis, you or your loved one can receive treatment for their symptoms. You can also benefit from community resources and information about caring for a loved one with LBD.

How LBD is diagnosed

Doctors start the assessment for diffuse Lewy body dementia by talking to the patient and their family to learn about the symptoms they're experiencing. A progressive decline in cognitive ability is one of the primary symptoms they look for, but two core symptoms of the following must be present:

  • Fluctuating alertness and thinking problems

  • Visual hallucinations

  • Parkinsonian symptoms

  • REM sleep behavior disorder

If you are experiencing symptoms involving thinking and memory issues, it may be helpful to bring a family member to doctor’s appointments so they can help you understand and remember what the doctor is telling you. Someone close to you may also help give a full picture of the symptoms you’re experiencing, such as noting when visual hallucinations occur or discussing a loss of cognitive function that they’ve noticed. 

Vital signs

The doctor may check your vital signs and ask you to do so at home for a period as well. They often look for blood pressure, heart rate, and body temperature instability. They may also note autonomic changes like sweating, excessive sleepiness, and loss of the sense of smell.

Monitoring symptoms at home can help ensure doctors have a complete overview of how your body is performing. For example, symptoms such as orthostatic hypotension, which is low blood pressure when you stand up after sitting or lying for a period of time, may not always be apparent after a single doctor’s visit. 

Neurological and cognitive exam

To check for Parkinsonian symptoms, the doctor may check your muscle tone, eye movements, reflexes, strength, balance, and gait. The doctor may give you a pen and paper or an oral test to test for cognitive symptoms like memory loss or a decline in thinking abilities. 

The one-year rule: Parkinson’s disease dementia vs. Lewy body dementia

Knowing how long the symptoms have been going on can benefit your doctor. Doctors use the one-year rule for distinguishing between Parkinson's disease and dementia with Lewy bodies. If cognitive difficulties occur for more than a year before movement problems start, the diagnosis is the movement disorder Parkinson's disease dementia. Lewy body dementia is more appropriate if the cognitive symptoms start simultaneously or at least a year before the movement problems begin.

Testing for diffuse Lewy body dementia

One of the first steps your doctor may take is tests to rule out other diagnoses. For example, they might give you a blood test to ensure your problem isn't due to an underactive thyroid.

Your doctor may also do imaging tests to support the diagnosis if they determine that you have diffuse Lewy body dementia. There are no definitive answers the doctor can gain through tests alone. However, the tests may still be helpful. These can include PET scans, single-photon emission computerized tomography (SPECT), tests to check nerve function in the heart, or sleep studies to monitor brain wave activity.

Treatment for diffuse Lewy body dementia

There's no cure for diffuse Lewy body dementia (LBD) yet. However, clinical trials are continually being conducted as experts develop treatments that will slow the disorder’s progression and improve quality of life in individuals with the disorder. Some medications and treatments may reduce the severity of behavioral, movement, and cognitive symptoms in people with Lewy body dementia, including the following.  


Clinical trials continue to test the efficacy of various medicines in the treatment of Lewy body dementia. People with Lewy body dementia often find that medications can slow the progression of cognitive decline, minimize Parkinsonian symptoms, and relieve other symptoms. These medications could include:

  • Cholinesterase inhibitors to improve alertness and memory

  • Parkinson's medications to reduce movement problems

  • Medications to relieve other symptoms, like sleep disorders or movement problems

Consult a doctor before starting, changing, or stopping any medication for your condition or symptoms. 


Various therapies are available to help people with diffuse Lewy body dementia. These therapies can help LBD patients function better in their daily activities, be more physically comfortable, and cope with emotional challenges. These options may include speech, occupational, physical, and other types of therapy, as well as support groups. Specialists may also help with specific symptoms, such as offering guidance on managing sleep disorders that often accompany the condition. 

Individual psychotherapy and family therapy

Individual and family therapy are available for people with diffuse Lewy body dementia and those who care for them. Therapy has both practical and emotional benefits. A therapist can teach problem-solving skills, relaxation techniques, and coping methods. Caregivers, especially family members who may struggle to see their loved one in this state, can benefit from these techniques. 

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Alternative treatment options 

When someone is diagnosed with LBD, it may affect them and their loved ones. Reaching out for help may be challenging if caregiving schedules or one's disability makes it challenging to leave home. Online therapy through a platform like BetterHelp can provide the support patients and caregivers seek to navigate the challenges they're experiencing.  

A potential benefit of online therapy is attending sessions from the comfort of your home, or anywhere you have an internet connection. Whether fitting caregiving into a busy work schedule or trying to coordinate family sessions for multiple people, online therapy can be convenient. 

Studies show that online therapy is effective, leading to a 50% improvement in symptoms of depression, generalized anxiety, and other mental health conditions and significantly decreasing the impact of stress and chronic fatigue. 


Diffuse Lewy body dementia is a common degenerative dementia, second only to Alzheimer's. Treatment may involve medications and therapy to help reduce the severity of symptoms. If you or someone you love has been diagnosed with LBD, therapy may help you work through any complicated emotions about your symptoms or prognosis. You're not alone, and compassionate support is available.
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