NEFL and Parkinson disease: In the Lund cohort, blood levels of NfL correlated with age in the whole cohort (ρ = 0.449, p < 0.001), in controls (ρ = 0.436, p = 0.001), and in patients with PD (ρ = 0.577, p < 0.001), but not in patients with APD (i.e., PSP, MSA, or CBS).