With the extra numbers of participants recruited onto the present study (total of 198 patients with PD and 91 healthy controls) we now find that the mean level of phosphorylated α-syn is significantly higher (p = 0.012) in the PD group than in the control group, and we confirm that this is not the case for ‘total α-synuclein’ (p = 0.058). Here, SNCA is linked to Parkinson disease.