Lewy Body Dementia: Symptoms, Causes, Risk Factors, and Diagnosis

Lewy body dementia is one of the most common forms of dementia, accounting for 20 to 30 percent of all dementia cases worldwide. But scientists know less about LBD, and they have fewer tools available for diagnosing and managing the condition. 

The exact cause of LBD is currently unknown, but scientists believe that abnormal aggregates of misfolded proteins play an important role. Lewy bodies, made up of clumps of proteins called alpha-synuclein, gradually build up and spread across different regions of the brain. 

Lewy bodies disrupt cellular processes, leading to dysfunction and eventual cell death. The damage reduces the levels of important neurochemical signals like acetylcholine. Lewy body pathology also reduces dopamine, contributing to motor symptoms.

Lewy bodies affect many brain regions, including the: 

• Brainstem. Responsible for regulating sleep, alertness, and helping control movement.
• Limbic system. Responsible for processing emotion, behavior, and memory.
• Hippocampus. Helps form memories.
• Midbrain and basal ganglia. Involved in involuntary movement and balance.
• Olfactory pathways. Involved in smell sensing and processing.
• Cerebral cortex. Responsible for higher-level functions like thinking, planning, and executive function.     

What is Lewy body dementia?

Lewy body dementia (LBD) is a progressive brain disorder and the second most common type of dementia after Alzheimer’s disease. It develops when abnormal protein deposits called Lewy bodies build up in the brain, disrupting memory, movement, behavior, and sleep.

Doctors recognize two main types of LBD: dementia with Lewy bodies and Parkinson’s disease dementia. Both forms share many symptoms with Alzheimer’s and Parkinson’s, which can make diagnosis challenging.

The two types of Lewy body dementia

• Parkinson’s disease dementia. This form of LBD occurs when Lewy bodies spread from the brainstem to the rest of the brain. People first develop Parkinson’s symptoms that affect movement, and later develop cognitive decline. As many as 80 percent of people who develop Parkinson’s will eventually develop dementia.
• Dementia with Lewy bodies. This form of LBD occurs when Lewy bodies start building up across multiple regions of the brain, leading to fluctuations in cognitive abilities and hallucinations.

Like other dementias, Lewy body dementia progresses over time. While every person’s experience is different, specialists often describe Lewy body dementia stages — from early changes in attention, sleep, or movement, to more advanced memory loss, hallucinations, and physical decline. Understanding these stages can help families anticipate care needs and plan for the future.

What causes Lewy body dementia?

While doctors can’t predict with certainty who will develop LBD, certain factors increase the risk of developing the disease. 

Lewy body dementia risk factors

• Age. Most people develop LBD after age 50.
• Sex. Men are more likely than women to develop LBD. 
• ApoE4 gene. The strongest genetic risk factor for Alzheimer’s disease may also increase the chances of developing LBD (though this association is much more established in Alzheimer’s).
• GBA gene. Mutations in the GBA gene may make individuals more susceptible to developing Parkinson’s disease and LBD.
• Rapid eye movement sleep behavior disorder. People with a rare disorder that causes people to act out their dreams are at a higher risk of developing both Parkinson’s and LBD.

Unlike Alzheimer’s or vascular dementia, there aren’t any specific lifestyle factors linked to LBD risk. However, newer studies suggest that a healthy diet, exercise, and cognitive stimulation may be protective. 

LBD symptoms: cognition, mood, movement, sleep, and more

The symptoms of Lewy body dementia vary from person to person, depending on the brain regions affected by Lewy bodies. 

How does Lewy body dementia affect cognition and memory?

People with LBD don’t produce enough of an important neurotransmitter called acetylcholine, which is linked to cognitive and memory problems, including:

• problems with thinking, attention, planning, and spatial abilities
• problems with memory, often occurring later in the course of the disease
• unpredictable fluctuations in concentration, attention, alertness, and wakefulness from day to day
• visual hallucinations, involving seeing things that aren’t there

How does Lewy body dementia affect mood and behavior?

Since Lewy bodies affect the limbic system, people with Lewy body dementia experience changes in mood and behavior, leading to psychiatric symptoms, including:

• Apathy
• Agitation
• Depression
• Delusions
• Paranoia

How does Lewy body dementia affect movement?

Both Lewy body dementia and Parkinson’s disease involve the buildup of Lewy bodies and cell death in the midbrain and basal ganglia. Cell death in these regions leads to movement-related symptoms: 

• Slow movements
• Muscle stiffness or rigidity
• Shuffling walk
• Shaking or tremors
• Problems with balance, posture, and coordination
• Small handwriting
• Limited facial expressions
• Difficulty swallowing
• Vocal problems

How does Lewy body dementia affect sleep?

Sleep-related symptoms are also common in Lewy body dementia, including:

• Trouble falling asleep
• Acting out dreams
• Sleeping for long periods during the day
• Restless legs syndrome 

Other symptoms of Lewy body dementia

Since Lewy body dementia affects the brain stem and smell regions of the brain, it causes a range of other symptoms including:

• Trouble regulating blood pressure or body temperature
• Fainting and frequent falls
• Constipations
• Urinary incontinence
• Changes in sensitivity to hot and cold
• Problems with smell
• Sexual dysfunction

Can you have Lewy body dementia and Alzheimer’s at the same time?

Another complication in diagnosis: Yes, it is possible to have both Lewy body dementia and Alzheimer’s disease at the same time. In fact, it isn’t so rare: A 2023 autopsy-based study published in the journal Brain found that many people diagnosed with one neurodegenerative disease might also have hallmark signs of other forms of dementia in the brain. Around three quarters of people who died with Lewy body dementia showed signs of other protein plaques, characteristic of diseases like Alzheimer’s or amyotrophic lateral sclerosis.  

Frequently asked questions about Lewy body dementia

What is the first symptom of Lewy body dementia?
The earliest signs can vary, but many people experience changes in thinking and attention before noticeable memory loss. Subtle movement changes, visual hallucinations, or fluctuations in alertness may also be among the first symptoms.

Is Lewy body dementia fatal?
Lewy body dementia itself is not a direct cause of death. That said, the complications it creates —  falls, infections, difficulty swallowing — can be life-threatening. Like other progressive dementias, LBD does shorten a person’s life expectancy.

How long can you live with Lewy body dementia?
Every case of LBD is different. Some people live a decade or more with LBD. The course of the disease depends on overall health, age at diagnosis, and the severity of symptoms. And the life expectancy after a diagnosis depends on how far along in the disease someone is when they get diagnosed.

What makes Lewy body dementia different from Alzheimer’s?
While Alzheimer’s disease is most strongly linked to memory loss, Lewy body dementia is often marked by early changes in attention, problem-solving, and movement. Visual hallucinations and rapid fluctuations in cognition are also more common in LBD than in Alzheimer’s.