SNCA and Cognitive impairment: It has been found that PD patients with rs356219/G had earlier onset age (Brockmann et al., 2013) and worse cognitive function (Campelo et al., 2017), probably affected by the distinction of SNCA expression in brain regions, blood, and plasma (Lesage and Brice, 2012; Brockmann et al., 2013; Burciu et al., 2018), whereas it was firstly shown in our study that rs356219/G reduces the risk of disease progression and cognitive impairment, which was not contradictory with previous studies.