Secondarily, conversion to dementia was analyzed with Kaplan-Meier-analysis once the MoCA was < 21.<h4>Results</h4>There was no significant difference in cognitive decline between PD<sub>GBA1+DBS+</sub> and PD<sub>GBA1+DBS-</sub> (-0.24 MoCA points/year; 95% confidence interval [CI] = -1.11 to 0.70) projecting to -0.72 MoCA points at 3-year-follow-up (p = 0.583). This evidence concerns the gene GBA1 and Parkinson disease.