A New Frontier to Understanding Cognitive Decline in Parkinson’s Disease 

By Tim Hague Sr. & Dauda Sulaiman Dauda | June 2025 

Recent research has uncovered a fascinating link between the bacteria in our mouths and guts and the progression of cognitive decline in Parkinson’s disease (PD). Scientists at King’s College London have found that changes in the microbiome (the community of bacteria living in our bodies) may play a role in worsening symptoms, particularly memory loss and dementia. For people living with PD and their loved ones, these findings offer hope for earlier detection and new strategies to help manage symptoms.

What Did the Scientists Discover?

The King’s College scientists examined 228 stool and saliva samples from 88 people with PD (41 of whom had mild memory changes, the other 47 had dementia) and compared them to 26 healthy individuals. They discovered that people with PD who had cognitive decline also had more harmful bacteria in their guts, many of which likely came from the mouth. This process, called “oral-gut translocation,” means that bacteria normally found in the mouth are making their way into the gut, where they don’t belong.

These bacteria release toxins known as “virulence factors,” which may damage gut tissue, trigger inflammation, and even affect brain function. Using artificial intelligence, the scientists were able to link these specific toxins to cognitive decline in PD, something traditional testing methods have been missing.

Why Does This Matter for People with PD?

This research adds an important piece to the PD puzzle: the oral–gut-brain connection. Scientists have long known that the gut microbiome can influence our brain. What’s new is the role that oral bacteria play when they sneak into the gut.

The study highlights the importance of maintaining good oral hygiene and a balanced diet. As PD progresses, routine care like brushing teeth and eating nutritious meals can become more challenging.  However, the research findings highlight how crucial it is to maintain good oral hygiene and nutrition, not just for general health, but potentially to help protect the brain.

Aside from shifting the paradigm towards a greater focus on the whole-body picture of PD, beyond just motor symptoms, the findings of this research open the door to new and exciting possibilities:

• Early Detection: One of the most promising aspects of this discovery is the potential for early detection. Changes in mouth and gut bacteria could serve as early markers for doctors to identify people with PD who are at higher risk of developing dementia. This could lead to earlier interventions and more personalized care.
• Potential New Treatments: In the future, treatments could focus on modifying the gut environment to slow or prevent dementia in PD patients. Researchers are already exploring whether microbiome-targeted therapies like probiotics, dietary changes, or even oral hygiene programs could make a difference.

 What Can You Do?

While scientists are still working to fully understand how these bacteria influence PD, there are practical steps you can take now. The good news is that many of the steps to protect your mouth and gut health are within reach and include:

• Staying on Top of Oral Hygiene: Brush and floss regularly, and see your dentist for check-ups. If you need help, ask your care team or loved ones for support.
• Eating a Balanced Diet: A diet rich in fiber, fruits, and vegetables can support a healthy gut microbiome.
• Limiting Sugar and Processed Foods: These can promote the growth of inflammation-triggering bacteria.
• Monitoring Your Thinking and Memory: If you or a loved one notices changes, speak with a neurologist. Early intervention matters.
• Engaging Your Healthcare Provider: Ask about ways to support your gut and oral health as part of your PD care plan. As one researcher put it: “Looking after your mouth and gut could be a powerful way to protect your brain.”

As always, stay informed and talk to your healthcare team about any changes in your symptoms or concerns about your health. Together, we can use the latest science to help you “Live your Best” with PD.

Reference:

Clasen F. et al., “Microbiome signatures of virulence in the oral-gut-brain axis influence Parkinson’s disease and cognitive decline pathophysiology,” Gut Microbes (2025). DOI: 10.1080/19490976.2025.2506843.

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