Wang et al. [31] found a protective association between T-rs11931074 allele carriers and motor severity. Ritz et al. [50] found that REP1-263 bp and G-rs356165 alleles increased the risk of faster decline of motor function, whereas Markopoulou et al. [43] demonstrated that REP1-263 bp allele reduced the risk of developing motor impairments
Markopoulou et al. [43] showed an increased risk of cognitive impairment in carriers of REP1-259 bp allele. Guella et al. [33] found a significant association of C-rs10018362, T-rs7689942, and G-rs1348224 alleles with PD with dementia
In Chen et al.’s study [34], TT-rs11931074 genotype increased the risk of hyposmia in PD
See Table 1. Questionnaires used: Unified Parkinson Disease Rating Scale-III and Hoehn and Yahr. Questionnaires used: Mini-Mental State Examination, Frontal Assessment Battery, Montreal Cognitive Assessment, Scales for Outcomes in Parkinson’s Disease Cognition, Hopkins Verbal Learning Test-Revised, Letter-Number Sequencing Test and Trail Making Test, Semantic and Phonemic Verbal Fluency Tests, and Benton Judgment of Line Orientation test. Questionnaires used: Hamilton Rating Scale for Depression and Anxiety and Beck Depression Inventory. Questionnaires used: REM Sleep Behavior Disorder Questionnaire, and Scales for Outcomes in Parkinson’s Disease Autonomic, Nighttime Sleep, Daytime Sleepiness and Psychiatric Complications.