SNCA and Parkinson disease: The plasma concentrations of total or pS129-α-synuclein did not correlate with age in controls or patients with PD (total α-synuclein r = 0.12 (95% CI: −0.12–0.53), p = 0.20; pS129-α-synuclein: r = 0.05 (95% CI: −0.25–0.35), p = 0.73, Spearman correlation analysis), which is consistent with our previous study focusing on total α-synuclein [21].