NEFL and Parkinson disease: Moreover, NfL also positively correlated with p-tau load in PDD/DLB (r = 0.42, R2 = 18%, P < 0.001) and PD (r = 0.31, R2 = 10%, P = 0.014), but not in controls across all regions (P = 0.579) (Fig. 4d).