Parkinson's disease (PD) affects nerve cells, including those in the gut. The gut has its own nervous system called the enteric nervous system, which acts like a "second brain." This study aims to find early signs, called biomarkers, of Parkinson's in the gut to improve early diagnosis. Researchers will collect samples during a routine colonoscopy, a test used to check the colon. This study is for people aged 45 and over who are due for a colonoscopy.

• The study only involves one visit during a routine colonoscopy.
• Participants will help discover early signs of PD, aiding in faster diagnosis.
• No extra medical procedures beyond the routine colonoscopy are needed.

Participants must be 45 to 75 years old and either have PD or be at risk for it. People with certain other diseases, like Alzheimer's or active cancer, cannot join. This study hopes to better understand the connection between the gut and brain in Parkinson's disease.