This study is about a disorder called *REM sleep behavior disorder* (RBD), where people act out their dreams. Some with RBD might later develop diseases like Parkinson's or dementia. The study is preparing for future treatment trials to protect nerve cells. People with RBD and healthy individuals will be part of the study. The NAPS2 group will gather information through tests, blood samples, brain scans, and sleep studies. Synucleinopathies are diseases related to a specific protein that can cause nerve issues.

Key Points:

• The study involves tests over time, including sleep studies and brain scans.
• Participants should be over 18 and capable of giving consent.
• There are specific health criteria to join; some health conditions may exclude you.