Finally, our study with the – to date – longest longitudinal follow-up of GBA1NMC of up to 9 years demonstrates that even in genetically-defined at-risk populations larger, multicenter studies with higher numbers of carriers of severe GBA1 mutations and even longer follow-up periods are highly warranted and might be necessary to delineate trajectories of motor, non-motor and fluid biomarkers to predict conversion to PD and/or cognitive decline and to inform clinical trials that target GBA1. This evidence concerns the gene GBA1 and Parkinson disease.