Recent studies [18,19] showed that age, genetic variation in Microtubule-Associated Protein Tau (MAPT), Apolipoprotein-E (APOE), gait disturbance, motor and non-motor assessments, dopamine transporter (DAT) imaging, electroencephalograms, and CSF biomarkers may contribute to the early prediction of cognitive impairment in PD. This evidence concerns the gene SLC6A3 and Parkinson disease.