We tested this hypothesis in the PPMI cohort [10] and found a significant relationship between phenotypic Axis 1 and the cerebrospinal fluid (CSF) Aβ1-42 level (r2 = 0.43, p = 0.007), an Alzheimer’s-associated biomarker strongly associated with future conversion to dementia, but no correlation was observed with total Tau, phosphorylated Tau or Alpha-Synuclein levels (p > 0.05). Here, SNCA is linked to dementia.