Several predictors have been proposed as markers for ongoing cognitive decline in PD, including age, genetic variation in APOE and MAPT, gait disturbance, motor assessments, non-motor symptoms, electroencephalogram analysis results, cognitive profiles, as well as several plasma biomarkers (e.g., α-synuclein/Aβ40, MIA, CRP, and albumin)13–16. This evidence concerns the gene APOE and Parkinson disease.