NEFL and Parkinson disease: The specific NFL concentrations were 11.8 ± 2.4, 15.0 ± 2.6, 19.6 ± 1.1, and 22.2 ± 1.9 pg/ml for the control, PD with normal cognition, PD-MCI, and PDD groups (n = 60, n = 102, n = 31, n = 13), respectively (F = 114.8, p < 0.001).