The proposed Neuronal α-Synuclein Disease Integrated Staging System (NSD-ISS) was recently applied to early Parkinson's disease (PD) cohorts. We applied this research framework to the BioFIND study cohort, which includes more moderately advanced PD participants with clinically established PD. Disease durations within each ISS stage were highly variable. Cognitive and non-motor anchors had little weight in determining staging. The analysis highlights strengths and limitations of NSD-ISS to guide further refinement of an integrated staging system.