What Is Lewy Body Dementia? 5 Main Symptoms

Get the facts about Lewy body dementia

Lewy body dementia is a progressive, degenerative brain disease. It’s the third most common form of dementia, after Alzheimer's disease and vascular dementia.

It can be a confusing type of dementia because there are some similar symptoms to those found in Alzheimer’s, but loss of short-term memory isn’t common.

It can also be challenging to diagnose because some of the symptoms have significant overlap to Parkinson’s disease.

We explain what Lewy body dementia is, how it’s different from Alzheimer’s and Parkinson’s, and the 5 main symptoms of the disease.

What is Lewy body dementia?

It’s called Lewy body dementia because the disease is associated with the abnormal buildup of proteins in the brain into masses known as Lewy bodies.

When they build up, they cause problems with the way the brain works, including memory, movement, thinking skills, mood, and behavior.

There are two forms of Lewy body, dementia with Lewy bodies and Parkinson’s disease dementia.

In dementia with Lewy bodies, the first symptoms are like the memory disorders seen in Alzheimer's disease.

Later, the person will develop movement problems similar to motor symptoms of Parkinson as well as other Lewy body symptoms.

In Parkinson’s disease dementia, the person first develops a movement disorder that looks like Parkinson’s, but later develops dementia symptoms. Their physical symptoms may also be milder than in typical Parkinson’s.

How Lewy body dementia is different from Parkinson’s or Alzheimer’s

Lewy body dementia is similar to and often confused with Parkinson’s or Alzheimer’s.

Even though they are different diseases, there are some differences in the symptoms and when those symptoms happen.

Lewy body may not cause short-term memory loss that happens with Alzheimer’s. In Lewy body disease, problems with thinking, alertness, and paying attention will come and go. 

A sign that your older adult could have Lewy body rather than another dementia is if they have symptoms of cognitive decline without the typical short-term memory problems. 

For example, Lewy body often causes hallucinations, especially in the first few years. With Alzheimer’s, hallucinations usually don’t show up until the later stages. 

People with Lewy body also have REM sleep behavior disorder, which causes them to act out their dreams and make violent movements while asleep. This is not common in Alzheimer’s.

Both Lewy body and Parkinson’s cause movement problems, but Parkinson’s doesn’t cause problems with thinking and memory until the later stages of the disease – and sometimes it doesn’t happen at all. 

With Lewy body, the cognitive problems start much sooner. That’s why doctors and researchers typically use the “1-year rule” to help make a diagnosis. 

If cognitive symptoms appear at the same time as or at least a year before movement problems, the diagnosis is likely to be dementia with Lewy bodies. 

But if cognitive problems develop more than a year after the onset of movement problems, the likely diagnosis is Parkinson's disease dementia.

Because of these differences, the treatments and medications used for Lewy body dementia are not always the same as the ones used to treat Parkinson’s or Alzheimer’s.

5 main symptoms of Lewy body dementia

There are 5 groups of symptoms that are common in Lewy body dementia. They will get worse over time, usually over several years.

1. Cognitive impairment

• Extreme swings between being alert and being confused or drowsy – episodes are unpredictable and could last a few seconds to several hours
• Reduced attention span
• Difficulty with planning, decision-making, organization
• Problems with visual perception (judging and navigating distances) – often causing falls or getting lost in familiar places
• Increased trouble with the tasks of daily living

2. Visual hallucinations
Another common symptom is repeated visual hallucinations or delusions – like seeing shapes, colors, people, or animals that aren't there. They may also have conversations with people who are deceased.

3. Movement symptoms

• Slow movement
• Shuffling walk or abnormal gait
• Stiff limbs
• Tremors
• Lack of facial expression

4. Sleep disturbances

• Insomnia
• Daytime sleepiness
• REM sleep behavior disorder – acting out dreams while asleep: physically moving, sleep talking, screaming, hitting, or even getting up and engaging in daytime activities

5. Fluctuations in autonomic processes
Lewy body may also cause problems with bodily functions that are automatic, including blood pressure, body temperature, urination, constipation, and swallowing.

Lewy body dementia life expectancy

The average person usually lives 5 to 7 years after a Lewy Body dementia diagnosis. But some people with LBD live up to 20 years after their diagnosis.

Unlike other dementias, Lewy body doesn’t follow a pattern of stages. The disease will continue to get progressively worse, but the rate of decline is different in each person.

Recommended for you:

• How to Understand and Manage Dementia Behaviors: A Comprehensive Guide
• Medications Worsen Dementia and Increase Dementia Risk: Anticholinergics
• 8 Forms of Dementia You Might Not Know About

By DailyCaring Editorial Team

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About the Author

Connie Chow

Connie was a hands-on caregiver for her grandmother for 20 years. (Grandma made it to 101 years old!) She knows how challenging, overwhelming, and all-consuming caring for an older adult can be. She also knows how important support is — especially in the form of practical solutions, valuable resources, and self-care tips.