NEFL and Parkinson disease: Higher concentration of NfL was associated with the presence of parkinsonism (β = 0.08, 95% CI 0.02–0.14, p = 0.006), and lower P-tau231 was associated with fluctuations of cognition (β = −0.18, 95% CI −0.33 to −0.02, p < 0.05; eFigure 3).