NEFL and Parkinson disease: The AUC for PD-CN conversion to MCI or dementia at follow-up time was determined to be 0.684 (95% CI 0.569–0.799), and the optimal cut-point for serum NfL levels was identified as 12.65 pg/mL (with a sensitivity of 71.4% and specificity of 64.6%), as illustrated in Figure 4.