Japan Parkinson's Progression Markers Initiative (J-PPMI).

Pathological changes of Parkinson's disease begin before the advent of motor symptoms. At the onset of Parkinson's disease (PD), already half of dopaminergic neurons are degenerated. It is useful to reveal the time course in the prodromal PD in order to establish the early diagnosis markers and the modifying therapies for PD. The Japan Parkinson's Progression Markers Initiative (J-PPMI) is longitudinal, multi-center study to assess the progression of clinical features, imaging and biological markers in the prodromal phase of synucleinopathy (PD, Lewy body dementia and multiple system atrophy). Subjects of J-PPMI are patients with the rapid eye movement sleep behavior disorder (RBD) which is known as a high risk factor for the development of Parkinson's disease.