Key Points

Specific changes in the gut microbiome have been associated with the shift from mild memory issues to dementia, a common and distressing symptom of the disease.

While Parkinson's is currently very difficult to diagnose in its early stages, these changes in the microbiome could potentially act as early warning signs of Parkinson's, said the researchers from King's College London.

It may help doctors detect and treat the disease before symptoms become severe.

"The human gut and oral bacterial communities are increasingly linked to neurodegenerative diseases. Disruptions in the gut-brain axis could trigger inflammation and immune responses that contribute to neuronal damage,” said Dr. Saeed Shoaie, group leader of the Quantitative Systems Biology (QTS) Lab at King's College London, UK.

In the study, published in the journal Gut Microbes, researchers analysed gut and mouth bacteria collected from 228 samples of stool and saliva.

This included two groups of patients with Parkinson's -- those with mild cognitive decline and those with dementia -- showing different stages of the disease. These were compared with a healthy control group with no Parkinson's diagnosis.

The results showed clear differences in the types and functions of bacteria between the groups. In people with cognitive impairment, the gut contains more harmful bacteria, many of which likely come from the mouth.

This process, known as "oral-gut translocation," involves oral bacteria moving into the gut, where they don't normally belong.

These bacteria were found to release specific molecules known as virulence factors, toxins that can damage gut tissue, promote inflammation, and possibly affect the brain.

"We don't yet know if the bacteria are causing the cognitive decline or if changes in the body due to Parkinson's allow these bacteria to grow. But our findings suggest they may play an active role in worsening symptoms," said Dr. Frederick Clasen, research associate at King's.

Using artificial intelligence (AI), the team linked these toxins specifically to cognitive decline in Parkinson's. These tools helped pinpoint bacterial species and functions that weren't obvious by traditional analysis alone.

"These toxins could be used as biological markers to identify patients at higher risk of dementia in Parkinson's. In the future, they might also be targets for new treatments that protect the brain by changing the gut environment," Dr. Clasen explained.

The findings also highlight the importance of oral hygiene and nutrition in people with Parkinson's, especially as the disease progresses.

- IANS