Lewy body dementia (LBD) is a general term for two different disorders of the nervous system: Parkinson’s disease dementia and dementia with Lewy bodies. Each of these forms of dementia affects parts of the brain, causing dysfunction with movement, behavior, and thinking.

Both types of LBD differ from Alzheimer’s disease, which is a separate condition from LBD. Alzheimer’s usually involves more memory problems and fewer movement disorder issues in the early stages of the disease. However, both Alzheimer’s and LBD affect cognitive function, causing problems with memory and thought processes.

Despite the similarities between the symptoms of LBD and Alzheimer’s disease, a neurologist or other properly trained specialist can help diagnose the difference between the two neurodegenerative conditions. In some instances, a health care specialist may diagnose someone with both LBD and Alzheimer’s disease at the same time.

Symptoms of Lewy Body Dementia

Both Parkinson’s disease dementia and dementia with Lewy bodies can cause noticeable mental or cognitive symptoms that can significantly affect quality of life.

Lewy bodies are clumps of material made up of a protein called alpha-synuclein. The buildup of these Lewy bodies in certain parts of the brain leads to both types of LBD. LBD is also linked to lower levels of dopamine and acetylcholine, two neurotransmitters or chemical messengers in the brain.

The difference between Parkinson’s disease dementia and dementia with Lewy bodies lies in the timing of when the cognitive impairment (thinking problems) and movement problems start happening.

Dementia With Lewy Bodies

Dementia with Lewy bodies causes the following most common symptoms (often showing up in this order):

• Rapid eye movement (REM) sleep behavior disorder
• Dementia
• Visual hallucinations
• Movement problems (parkinsonian motor symptoms)

REM Sleep Behavior Disorder

Normally, a person is paralyzed while in the REM phase of sleep and cannot act out a dream. REM sleep behavior disorder is a sleep issue when someone appears to act out their dreams, talking in their sleep, or moving wildly. This sleep disorder can often be the first symptom of LBD, showing up years before other symptoms.

Dementia

Dementia is a decrease in mental functions — specifically language skills, visuospatial awareness, problem-solving, attention, alertness, and memory. Memory is often the least affected of these mental functions.

Visual Hallucinations

When people see things in their visuospatial field that are not there, it’s called a visual hallucination.

Movement Problems (Parkinsonian Motor Symptoms)

Trouble walking, muscle stiffness (rigidity), tremors, and slowness of movement can occur. Clinicians refer to these movement problems as parkinsonian motor symptoms.

Parkinson’s Disease Dementia

This type of dementia looks similar to dementia with Lewy bodies during the later stages of the disease. However, in the early stages of Parkinson’s disease dementia, the Parkinson’s movement disorder comes first. Then, the other issues, such as dementia and visual hallucinations, follow suit.

Similarities Between LBD and Alzheimer’s

Although LBD is a completely different diagnosis than Alzheimer’s, they often share some of the same symptoms.

Both Alzheimer’s and LBD cause dementia. Dementia with Lewy bodies leads to earlier onset of dementia. Parkinson’s disease dementia develops later. People with either LBD or Alzheimer’s disease can also experience symptoms such as depression, anxiety, delusion, and paranoia.

Differences Between LBD and Alzheimer’s

There are key differences between LBD and Alzheimer’s. For example, a person with LBD will develop parkinsonian motor symptoms, whereas someone with Alzheimer’s disease does not have these movement symptoms as part of Alzheimer’s.

Unlike someone with Alzheimer’s only, someone with LBD may often have problems with autonomic function, such as:

• Abnormalities in blood pressure
• Difficulty controlling body temperature
• Constipation
• Urinary incontinence (when a person accidentally leaks urine)
• Dizziness
• Fainting spells
• Sexual dysfunction

People with LBD also have fluctuations in mental function. This means that their cognitive symptoms can change greatly from one day to the next — especially regarding attention and alertness. Those who have LBD experience visual hallucinations, and people with Alzheimer’s disease do not. A person with LBD can have REM sleep behavior disorder, which is not part of Alzheimer’s.

LBD or Alzheimer’s: Which Does Your Loved One Have?

A person must receive the correct diagnosis, whether it is LBD or Alzheimer’s, to receive proper care. For example, health care providers can prescribe antipsychotic medications (this treatment is still controversial) to someone with Alzheimer’s for their behavioral symptoms. However, antipsychotic medications can produce severe reactions in people with LBD.

The early stages of both LBD and Alzheimer’s can make it tough to distinguish between the two diseases. On top of that, it is common for someone to have both diseases at the same time. About 50 percent of people with LBD also have Alzheimer’s disease.

Caregivers, family members, and other loved ones can make an ongoing list of someone’s symptoms to share with a health care provider. This information will help lead to a proper diagnosis and management of either LBD or Alzheimer’s.

No medical test can diagnose LBD or Alzheimer’s with 100 percent certainty. However, to reasonably determine whether a loved one has either LBD or Alzheimer’s, a neurologist — or another properly trained medical specialist — will likely do the following:

• Take a detailed medical history, being careful to review the person’s symptoms, and speak with them and their caregiver
• Perform physical and neurological exams
• Order tests to rule out diseases that could lead to similar symptoms, including a blood draw or brain imaging studies
• Perform neuropsychological testing to gauge a person’s memory and other mental functions

Talk With Others Who Understand

On myALZteam, the social network for people with Alzheimer’s disease, more than 84,000 members come together to ask questions, give advice, and share their stories with others who understand life with Alzheimer’s.

Are you or someone you care for living with Alzheimer’s? Share your experience in the comments below, or start a conversation by posting on myALZteam.