Brain Inflammation Linked to Dementia Risk in Parkinson's Disease
Parkinson's disease (PD) is known primarily for its movement-related symptoms, but it can also lead to dementia, a devastating decline in cognitive abilities. Nearly half of people diagnosed with Parkinson’s develop dementia within 10 years of their Parkinson’s diagnosis. Researchers are now looking closer at what happens in the brain early in the disease to understand why some people with Parkinson’s develop dementia while others don't.
A new study, published in Brain, focused on two key factors: brain inflammation (also called neuroinflammation) and the buildup of a protein called tau. Neuroinflammation, an immune response within the brain that is largely protective when working correctly, can release harmful chemicals that can damage or kill neurons when overactive, impairing communication between brain cells essential for cognitive processes. Tau protein, when misfolded and accumulated, forms tangles that disrupt how brain cells transport nutrients, preventing them from functioning properly and eventually leading to cell death.
Both processes can contribute to the progressive loss of brain cells and synaptic connections and may ultimately lead to the cognitive decline characteristic of dementia. However, it was not known to what degree these factors were linked to dementia risk in people with early-stage Parkinson’s.
Study Results
The study enrolled 31 people recently diagnosed with Parkinson’s (the average time since diagnosis was one year) and 19 people of similar ages that did not have Parkinson’s. Using specialized brain scans (PET scans), researchers examined brain inflammation and tau accumulation in each participant. In addition, levels of body-wide markers of inflammation and tau were evaluated through a blood test.
The researchers also evaluated the participants’ potential risk for dementia by assessing visual-motor skills, word recall and results from a genetic test (MAPT genotype) that is linked to dementia. Based on these test results, they divided participants into two groups — those at higher risk or lower risk for dementia.
The study found that people at higher risk for dementia showed significantly more brain inflammation in several brain regions compared to both those at lower risk and people without PD. This inflammation was also linked to poorer performance on a cognitive test (ACE-III). Additionally, the overall level of neuroinflammation correlated with the amount of body-wide markers of inflammation seen in the blood test. This suggests that a high level of inflammatory markers detected in the blood may be a sign of increased neuroinflammation.
Interestingly, while tau protein buildup was observed, it didn't seem to directly relate to cognitive decline. However, the study did find that more brain inflammation was linked to tau accumulation, particularly in the high-risk group.
People with Parkinson's scored lower on a cognitive test (ACE-III) compared to those without Parkinson's. Even within the Parkinson's group, those at higher risk for dementia scored lower on the same test than those at lower risk. Interestingly, the group at higher dementia risk had been diagnosed with Parkinson's for a slightly shorter time but showed more severe Parkinson's symptoms. There was no link between higher risk of dementia and age, gender, or the amount of Parkinson's medication someone took.
Overall, these findings suggest that brain inflammation is evident in the early stages of Parkinson's and may be a key factor in determining who develops dementia. On the other hand, accumulation of tau protein in early-stage Parkinson’s does not appear to correlate with dementia risk.
Highlights
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The study enrolled 31 people who were recently diagnosed with Parkinson’s and 19 people of similar ages that did not have Parkinson’s. People with Parkinson’s were grouped into those with high- and low-risk for dementia.
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People with Parkinson's scored lower on a cognitive test (ACE-III) compared to those without Parkinson's.
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Using specialized brain scans (PET scans) and markers, researchers examined whether participants showed signs of brain inflammation and tau protein accumulation
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People at higher risk for dementia showed significantly more brain inflammation in several brain regions compared to those at lower risk and people without PD.
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Brain inflammation was also linked to poorer performance on a cognitive test (ACE-III).
What does this mean?
This study indicates that brain inflammation may be an early contributor to dementia in Parkinson’s disease. As a result, neuroinflammation could potentially be a useful biomarker to identify people with Parkinson’s who are at risk for dementia. This opens the door to potential treatments that target brain inflammation, possibly preventing or slowing the progression of dementia in people with Parkinson's disease. There are several anti-inflammatory treatments already licensed to treat other conditions, which could potentially be repurposed to help treat PD-related dementia. However, it could take many years before a treatment strategy to alleviate Parkinson’s-linked dementia becomes widely available.
What do these findings mean to the people with PD right now?
This study further solidifies the link between the brain inflammation people with PD experience and the risk for dementia. Parkinson’s disease dementia symptoms include potential thinking, memory and behavior changes — these symptoms can be wide-ranging. If you notice symptoms, talk to your movement disorders specialist about dementia concerns. While there is no way to stop the disease’s progression, a doctor can help manage the symptoms.
Learn More
The Parkinson’s Foundation believes in empowering the Parkinson’s community through education. Learn more about the topics in this article through our below resources, or by calling our free Helpline at 1-800-4PD-INFO (1-800-473-4636) for answers to your questions.
