Scientists have found new evidence that bacteria in the mouth and gut could be linked to memory problems in people with Parkinson’s disease.
The study, led by researchers at King’s College London, shows that changes in these bacteria—known as the microbiome—may be connected to how the disease progresses from mild forgetfulness to full dementia.
This discovery is important because Parkinson’s disease is hard to diagnose early. Symptoms develop slowly and may be missed until the disease has already caused damage.
But if changes in the microbiome can act as early warning signs, doctors might be able to detect and treat the disease before serious symptoms begin.
Researchers have long believed that the gut and brain are closely connected. This relationship, often called the “gut-brain axis,” means that what happens in your digestive system can affect your brain and nervous system. While this link has been studied for years, few studies have looked at how bacteria might influence memory loss in Parkinson’s disease.
In this study, scientists examined bacteria found in stool and saliva samples from 228 people. The participants were split into three groups: one with Parkinson’s disease and mild memory problems, one with Parkinson’s disease and dementia, and one healthy group without Parkinson’s. The team found clear differences in the types of bacteria present in each group.
People with memory problems had more harmful bacteria in their guts—some of which are normally only found in the mouth. This means that oral bacteria may be traveling to the gut in a process called “oral-gut translocation.” These bacteria can release harmful substances called toxins, which may damage the gut lining, cause inflammation, and potentially harm the brain.
One of the bacteria identified in earlier studies is Porphyromonas gingivalis, a common cause of gum disease. This bacterium has also been linked to Alzheimer’s disease, another condition that causes memory loss. In this study, the researchers found that harmful bacteria from the mouth were more common in people with advanced Parkinson’s.
Dr. Frederick Clasen, the lead author of the study, explained that it’s still not clear whether these bacteria cause memory loss or if Parkinson’s makes it easier for them to grow. But the presence of these bacteria and their toxins was clearly linked to worse symptoms.
The team used artificial intelligence tools to analyze the data more deeply. This helped them find specific bacterial species and their functions that weren’t easy to identify with regular methods. These findings could help scientists develop new ways to detect and treat Parkinson’s.
For example, the bacterial toxins might serve as early biological markers—signals in the body that show who is more likely to develop dementia. In the future, treatments might aim to block these toxins or adjust the gut environment to keep harmful bacteria from thriving.
The study also points to the importance of good oral hygiene and proper nutrition for people with Parkinson’s. As the disease progresses, patients may rely more on caregivers, and daily routines like brushing teeth or eating healthy meals may be overlooked. Taking care of oral and gut health could help slow down memory loss and other symptoms.
Dr. Saeed Shoaie, a co-author of the study, emphasized that looking after the microbiome—through tooth brushing, healthy eating, and possibly using probiotics—may offer new ways to manage Parkinson’s disease.
In conclusion, this research shows a strong link between the bacteria in the mouth and gut and the brain changes seen in Parkinson’s. While it doesn’t prove that these bacteria directly cause dementia, it opens the door to new ideas for early diagnosis and treatment.
Future studies will look at whether changing the microbiome can protect the brain and slow or even prevent cognitive decline in people with Parkinson’s.
If you care about Parkinson’s disease, please read studies that Vitamin B may slow down cognitive decline, and Mediterranean diet could help lower risk of Parkinson’s.
For more information about brain health, please see recent studies that blueberry supplements may prevent cognitive decline, and results showing Plant-based diets could protect cognitive health from air pollution.
The research findings can be found in Gut Microbes.
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