In these studies, longitudinal follow-up of the motor and cognitive functions, non-motor symptoms (e.g. hyposmia and RBD), blood and spinal fluid biomarkers, transcranial ultrasound, and dopamine transporter (DaT) single-photon-emission computed tomography (SPECT) were used to track the incidence of PD or DLB7–10. This evidence concerns the gene SLC6A3 and Parkinson disease.