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Disease Connections: Alzheimer’s and Parkinson’s

How are Alzheimer’s and Parkinson’s disease connected, and how does Parkinson’s disease dementia differ from Alzheimer’s? Learn about key similarities and differences between these two neurodegenerative diseases. 

Alzheimer’s disease and Parkinson’s disease are the two most common neurodegenerative diseases, impacting nearly 8 million people combined in the U.S. The number of people living with each disease is expected to double by 2050.

With the growing prevalence of these and other neurodegenerative diseases, research to determine how they are connected is critical. We know that when we make discoveries regarding one disease, it leads to a ripple effect that yields insights into many others. Below we outline some important connections and similarities between Alzheimer’s and Parkinson’s disease and explore how research into one disease may lead to advancements in diagnosis and treatment for others.

What Is the Difference Between Parkinson’s and Alzheimer’s?

Alzheimer’s and Parkinson’s are both neurodegenerative diseases caused by disruption and damage to certain parts of the brain, with more and more critical brain cells dying as the disease progresses. However, each disease has distinct symptoms due to the specific brain regions affected and how brain signals are disrupted. For example, the most common symptoms of Alzheimer’s disease are memory loss and having trouble thinking, while Parkinson’s mostly causes difficulty with movement and fine motor skills.

What Is Alzheimer’s Disease?

Alzheimer’s disease affects memory and thinking and accounts for 60% – 80% of all dementia cases. Early signs of Alzheimer’s may resemble basic age-related memory issues, but as symptoms progress, people experience severe memory loss, confusion, and difficulty thinking and performing daily tasks. 

What Is Parkinson’s Disease?

Parkinson’s disease primarily affects movement, with symptoms like tremor, slowed movements or freezing (the sudden inability to move), and loss of balance and coordination progressively getting worse over time. Dementia symptoms similar to those of Alzheimer’s can occur eventually in Parkinson’s disease, but they are not the primary symptoms.

Can Parkinson’s Cause Dementia?

While dementia usually isn’t a primary symptom of Parkinson’s disease, it is common in the later stages of the disease. Studies have shown that up to 70% of people with Parkinson’s will eventually develop dementia at some point. 

Though similar, Parkinson’s disease dementia is not the same thing as Alzheimer’s disease.  Dementia refers to a range of symptoms — including memory loss, trouble thinking, confusion, and difficulty concentrating — but there are multiple diseases that may cause dementia. The form of dementia many people with Parkinson’s eventually develop is typically a form of Lewy body dementia (LBD).

Alzheimer’s is the most common cause of dementia, but LBD, FTD-ALS spectrum disorders, Parkinson’s, and other diseases can cause these symptoms as well. Because so many different diseases involve dementia at some point in their progression, research breakthroughs in any one of these disease areas will likely shed light on the causes and symptoms of the others.

Alzheimer’s vs. Parkinson’s Disease: What Causes Neurodegenerative Diseases?

Both Alzheimer’s and Parkinson’s are neurodegenerative diseases researchers have linked to toxic protein clumps in the brain. In these cases, faulty versions of otherwise healthy proteins found in the brain form clumps and tangles that damage brain cells and disrupt brain function. For example, in Parkinson’s disease, these toxic buildups damage the parts of the brain responsible for movement.

There are three types of proteins commonly linked to neurodegenerative diseases like Alzheimer’s and Parkinson’s:

  • Beta-amyloid
  • Alpha-synuclein
  • Tau

While beta-amyloid clumps and tau tangles are more common in Alzheimer’s disease, Parkinson’s is mainly characterized by alpha-synuclein buildup. However, toxic buildups of each of these types of proteins may be found at different levels across a range of neurodegenerative diseases.

Can You Treat Alzheimer’s and Parkinson’s Together?

Alzheimer’s and Parkinson’s are generally treated with different medications and therapies tailored to their specific symptoms. 

Historically, the only treatments for Alzheimer’s were medications and therapies to help manage symptoms. However, several recently approved Alzheimer’s drugs have proven effective in reducing the amount of toxic amyloid-beta proteins that cause the disease. Researchers hope that a similar approach may soon result in treatments that can target the harmful protein clumps found in Parkinson’s and other neurodegenerative diseases.

In Parkinson’s, the brain loses the ability to create the chemical dopamine, which is involved in movement. For this reason, common Parkinson’s treatments include drugs to regulate dopamine levels and deep brain stimulation to trigger parts of the brain responsible for motor skills. People with Parkinson’s may also undergo physical therapy to help manage symptoms. While there are currently no approved drugs that can slow or halt the progression of Parkinson’s, researchers have made progress in early diagnosis — including developing a biomarker test to detect alpha-synuclein last year.

The links between diseases like Parkinson’s, Alzheimer’s, and other neurodegenerative conditions show that a breakthrough in one disease may lead to advancements in many others. At the American Brain Foundation, we know that investing in research across the full spectrum of brain diseases and disorders will lead to new diagnosis methods, treatments, and ultimately cures for a range of devastating brain diseases.

The American Brain Foundation was founded to bring researchers and donors together in the fight against brain disease. Learn more about brain disease or make a gift to support groundbreaking brain disease research.