Based on a subset of 50 PD patients who had longitudinal CSF biomarker data, more decrease in CSF α-synuclein concentration over time correlated with a steep increase of rD (PFDR = 0.03, r = -0.34) as well as aD (PFDR = 0.03, r = -0.33) in the ipsilateral substantia nigra. This evidence concerns the gene SNCA and Parkinson disease.