NEFL and Parkinson disease: Finally, the inclusion of other biomarkers related to cognitive impairment, such as fluid α‐synuclein, Aβ42/Aβ40, neurofilament light (NfL), and p‐tau 217, followed by the identification of the most effective individual biomarkers or a combination thereof, will have great clinical significance in the diagnosis and prediction of cognitive impairment in PD patients.