In the five results in Table 1C, the CSF α-synuclein level showed no association with any domains of cognitive assessment, including frontal/executive, attention, memory, visuospatial functions and others in PD without dementia (Buddhala et al., 2015; Stav et al., 2015), PD with normal cognition and MCI (Yarnall et al., 2014) and PD with a wide range of cognitive status (Kang et al., 2013; Førland et al., 2018). Here, SNCA is linked to Parkinson disease.