The Parkinson's Progression Markers Initiative (PPMI) has addressed a key gap in the availability of long-term longitudinal data in sporadic Parkinson's disease (sPD) with extensive biological characterization. With biological characterization in the neuronal synuclein disease (NSD) framework, longitudinal outcomes are observed in cohorts defined by biological characteristics rather than based on conventional clinical diagnostic criteria. We recently reported our observations on 5 years of follow up in this cohort, and here, we provide our earliest findings on a comprehensive long-term description of disease progression in 344 sPD participants followed for up to 11 years. Although data collection is ongoing, these early findings highlight the heterogeneity in the early PD population as defined by clinical diagnostic criteria and affirm the importance of shifting to biologically and functionally based criteria in clinical research studies. ANN NEUROL 2026.