GBA1 and dementia: Through the method of meta-analysis, there was significant difference in age at onset (MD = −3.10 [95% CI: −4.88, −1.32]), bradykinesia as an initial symptom (OR = 1.49 [95% CI: 1.15, 1.94]), having family history (OR = 1.50 [95% CI: 1.18, 1.91]), and dementia (OR = 3.21 [95% CI: 1.97, 5.24]) during the comparison between PD patients with and without GBA mutations.