Recruitment Strategies across the Spectrum of Neuronal Synuclein Disease.

The Parkinson's Progression Markers Initiative (PPMI) has remained at the vanguard of Parkinson's disease (PD) research through evolving recruitment strategies that mirror advances in PD biology. PPMI was initially focused on untreated, early-stage PD. Over time, it has expanded to include genetic cohorts, prodromal participants identified via olfactory testing and risk factor questionnaires targeting people with rapid eye movement (REM) sleep behavior disorder (RBD). Most recently, PPMI has focused on the biology underlying PD and sought to recruit individuals defined by neuronal alpha-synuclein disease (NSD) biomarkers. This evolution from clinical to biological enrollment demonstrates the feasibility of biomarker-driven cohort design and establishes a scalable model for early detection and prevention research in neurodegenerative disease. ANN NEUROL 2026.