Parkinson’s disease can result in problems with memory and thinking. Lewy bodies are sticky protein lumps that disrupt the normal functions of the brain and may be related to dementia in a person with Parkinson’s disease.

Lewy bodies are also a feature of some other brain conditions, including Alzheimer’s disease.

In this article, we discuss the types, symptoms, diagnosis, and treatment of Parkinson’s disease. We also cover Lewy bodies and how they can cause dementia.

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Parkinson’s disease is a neurological condition that develops slowly and primarily affects nerve cells in an area of the brain called the substantia nigra. The nerve cells in this region produce dopamine, which is a neurotransmitter that regulates various bodily processes, including movement. Death of the nerve cells leads to a depletion of dopamine.

The Parkinson’s Foundation estimates that nearly 1 million people in the United States have Parkinson’s disease, with experts predicting this number to increase to 1.2 million by 2030. Males are 1.5 times more likely than females to develop Parkinson’s disease.


Parkinson’s disease develops gradually over a number of years and can manifest differently in each person. Symptoms that a person may experience include:

  • tremor, or shaking, which usually starts in the form of a “pill rolling” tremor when a person is at rest
  • bradykinesia, which refers to slow movement or freezing when moving
  • rigidness in the limbs
  • problems with balance and walking

Learn more about the signs and symptoms of Parkinson’s disease.


There are different types of Parkinson’s disease. The main types include:

  • Idiopathic Parkinson’s disease: This is the most common type of Parkinson’s disease. Doctors use the term idiopathic to describe conditions with an unknown cause.
  • Vascular parkinsonism: Small strokes can cause and worsen this type of Parkinson’s disease.
  • Drug-induced parkinsonism: This type occurs due to certain medications, such as antipsychotic drugs or antidepressants. Most individuals recover within a few days, weeks, or months of stopping the causative drug, but in rare cases, it can be permanent.

Related conditions

About 15% of individuals with Parkinson’s disease symptoms have other related conditions. These are known as atypical Parkinsonian disorders, and researchers have linked them with irregular protein buildup in the brain and other changes in this organ. They include:

  • Dementia with Lewy bodies (DLB): DLB is associated with the abnormal buildup of alpha-synuclein protein in the brain.
  • Corticobasal syndrome (CBS): CBS, which is the least common atypical Parkinsonian disorder, usually appears after the age of 60 years and begins by affecting one limb.
  • Progressive supranuclear palsy (PSP): This is the most common degenerative type of atypical Parkinsonian disorder. PSP typically presents in a person’s mid-60s and is associated with the accumulation of tau protein in the brain.
  • Multiple system atrophy (MSA): MSA usually develops when a person is in their mid-50s. This condition is also linked with the abnormal buildup of alpha-synuclein.

The Alzheimer’s Association notes that 50–80% of people with Parkinson’s disease will experience dementia.

Dementia is the progressive decline of cognitive function, and it can result in changes in memory, behavior, and the ability to carry out tasks. The World Health Organization (WHO) estimates that nearly 50 million people in the world live with dementia and that there are almost 10 million new cases every year.

Research suggests that Lewy bodies play a role in several conditions that cause dementia. Lewy body dementia results from a buildup of Lewy bodies, which are abnormal deposits of a protein called alpha-synuclein. These deposits eventually damage brain cells, leading to dementia.

Experts believe that Lewy body dementia is the third most common type of dementia, accounting for 5–10% of cases. The condition causes memory loss, behavioral changes, and progressively worsening movement symptoms that are the same as those that occur in Parkinson’s disease.

There are two diagnoses of Lewy body dementia:

Parkinson’s disease dementia (PDD)

Doctors diagnose PDD when a person living with Parkinson’s disease experiences significant cognitive decline after at least 1 year of developing their initial symptoms. The symptoms may progress from mild to severe, resulting in a diagnosis of dementia.

PDD may result in difficulties with the following:

  • memory
  • speech
  • problem-solving
  • forgetfulness
  • attention
  • understanding abstract concepts

Individuals with PDD will usually require assistance as the dementia progresses and affects an individual’s ability to do daily tasks and take care of themself.


Doctors diagnose DLB when cognitive decline is the earliest symptom or when cognitive decline and motor symptoms begin and progress together.

A person with DLB may experience some of the following symptoms:

  • fluctuating changes in alertness and attention
  • recurring, detailed visual hallucinations
  • disturbed sleep, including movements such as hitting and yelling while asleep
  • movement problems, including slow walking
  • tremor
  • confusion

Less common symptoms of DLB include:

  • auditory hallucinations, or hearing sounds that are not real
  • repeated falls
  • fainting
  • constipation
  • incontinence
  • lack of enthusiasm, interest, or motivation

A person with DLB may also develop other conditions, such as anxiety and depression.

A person with Parkinson’s disease may develop dementia and have problems with reasoning and thinking. Lewy bodies are a feature of several brain disorders, including Parkinson’s disease and Alzheimer’s disease, and they may cause rigid muscles and problems with movement and posture.

Research suggests that the similarity of the symptoms of Parkinson’s disease and Lewy body dementia may be indicative of a shared link to how the brain processes alpha-synuclein.

It is not possible to test for the presence of Lewy bodies, so researchers must try to determine their effects by carrying out postmortem studies.

There is currently no cure for dementia. However, medication can alleviate the symptoms, while a team of medical professionals and therapists may help a person develop strategies to manage their daily activities.


Doctors may prescribe the following medications:

  • Antipsychotics: These drugs help treat behavioral and psychological symptoms of dementia. One example is haloperidol (Haldol).
  • Cholinesterase inhibitors: These drugs prevent the breakdown of a chemical called acetylcholine, which the body needs for memory and learning. An example of a cholinesterase inhibitor is rivastigmine (Exelon).
  • Clonazepam (Klonopin): This drug treats sleep disturbance.
  • Levodopa (Sinemet): Doctors use this drug to treat the motor symptoms associated with Parkinson’s disease and Lewy body dementia.

Care team

A person with dementia may have a dedicated care team to provide assistance. The team may include:

  • Neurologists: These professionals specialize in brain conditions, such as dementia.
  • Physical therapists: Physical therapists use exercises and training programs to help with mobility issues.
  • Speech-language pathologists: These specialists assist with problems relating to swallowing and speaking.
  • Occupational therapists: These therapists help individuals modify their home environment and carry out daily tasks, such as eating and bathing,
  • Mental health therapists: Mental health therapists help people with dementia cope with their condition and plan for the future.

Lewy body dementia is the progressive loss of cognition that results from the buildup of Lewy bodies, which leads to the degeneration of certain regions of the brain. Depending on when cognitive symptoms occur in Lewy body dementia, doctors may give a person a diagnosis of Parkinson’s disease dementia or dementia with Lewy bodies.

Dementia can lead to memory loss and impairment in thinking skills. As the condition worsens, other symptoms may also occur, including problems with walking, hallucinations, tremor, and confusion. Although there is no cure for dementia, a combination of medication and therapy may help an individual adjust to their diagnosis and maintain their independence.