Insulin resistance is associated with cognitive dysfunction42 and, even in de novo PD patients in the prediabetic range, was shown to lead to faster rates of decline in cognitive performance than nondiabetic/normoglycemic patients with PD.15 Dysfunctional neuronal insulin signaling leads to increased aggregation of amyloid‐ß, hyperphosphorylated τ, proinflammatory pathway activation, and impaired brain glucose metabolism,43 and thus may explain accelerated decline in cognition in PD. This evidence concerns the gene INS and Parkinson disease.