Parkinson's Disease and Lewy Body Dementia Explained

Parkinson's disease and Lewy body dementia (LBD) are degenerative brain disorders. Both diseases are linked to protein deposits in the nerve cells of the brain known as Lewy bodies. 

The two disorders have similar symptoms. People with LBD may experience tremors and muscle stiffness like those who have Parkinson's. And, while Parkinson's disease affects motor function, about 40% of people with Parkinson's also develop dementia as the disease advances.

Here's a closer look at the connection between Parkinson's disease and Lewy body dementia.

What Are Lewy Bodies?

Healthy brains contain alpha-synuclein, a protein that's important to neuron function. In some people, alpha-synuclein begins to clump inside the neurons, forming what's called Lewy bodies. This protein buildup affects how cells communicate and impacts brain function. Over time, the damaged nerve cells die.

What Is Lewy Body Dementia?

About 1.4 million Americans have Lewy body dementia, a brain disorder that impacts cognitive and motor functions. It can cause:

• Difficulties related to memory, language, judgment and learning
• Muscle rigidity and slow movement
• Vivid dreaming and violent movements during sleep
• Apathy, depression and anxiety

LBD is a degenerative disease. As symptoms get worse, it becomes more difficult for people with the disorder to complete daily tasks and independently care for themselves.

Types of Lewy Body Dementia

There are two types of Lewy body dementia. A person may be diagnosed with either:

• Dementia with Lewy bodies
• Parkinson's disease dementia

The specific diagnosis depends on:

• Where in the brain Lewy bodies initially form
• When cognitive and motor skills are impacted

Dementia With Lewy Bodies

Dementia with Lewy bodies typically develops after the age of 60. This disorder results from the initial formation of Lewy bodies in the cerebral cortex or outer layer of the brain, which impacts memory, thought and perception. It may initially resemble Alzheimer's disease. 

Patients are usually diagnosed with dementia with Lewy bodies if cognitive and movement symptoms begin at the same time or within a year of each other. Some of the motor skills that are impacted include posture, balance, coordination and walking. Tremors may occur, but they're not as pronounced as in Parkinson's disease. 

While those who have dementia with Lewy bodies may have some cognitive difficulties similar to Alzheimer's, there are some symptoms unique to dementia with Lewy bodies:

• Hallucinations
• Delusions
• Difficulties staying alert
• REM sleep behavior disorder (violent movements during sleep)

Parkinson's Disease Dementia

Parkinson's disease dementia typically develops after age 70. This disorder results from the formation of Lewy bodies further in the brain stem, in the substantia nigra, which impacts motor skills. This causes symptoms usually associated with Parkinson's disease such as muscle stiffness, trembling, shaking and slow movement. In fact, people who develop Parkinson's disease dementia are usually first diagnosed with Parkinson's disease.

Patients are usually deemed to have Parkinson's disease dementia if cognitive symptoms begin a year or more after problems with motor skills appear. In most cases, dementia usually occurs about 10 to 15 years after movement is impacted.

Hallucinations are less common and movement symptoms are more severe in Parkinson's disease dementia compared to dementia with Lewy bodies.

Summarizing the Difference Between Parkinson's Disease and Lewy Body Dementia

Because Parkinson's disease and Lewy body dementia are both caused by the presence of Lewy bodies in the brain and result in similar symptoms, it can be confusing to understand the difference. Here's a quick summary:

Lewy body dementia is a blanket term referring to dementia caused by the presence of Lewy bodies. There are two types of Lewy body dementia: 

• Dementia with Lewy bodies
• Parkinson's disease dementia

Parkinson's disease is a progressive brain disorder that impacts movement, coordination and balance. The term Parkinson's disease doesn’t imply that dementia is present, and not all patients with Parkinson's get dementia. However, those who have Parkinson's are almost six times more likely to develop cognitive impairment compared to those of the same age without Parkinson's. People with Parkinson's disease who develop dementia are said to have Parkinson's disease dementia.

At this time, there's no prevention or cure for Parkinson's disease and Lewy body dementia. Doctors can recommend treatments and therapies to help ease symptoms and improve quality of life.