SIRT1 levels were significantly lower in PD patients, with a median of 109.5 ng/mL (IQR: 107–112) compared to 134.5 ng/mL (IQR: 132.8–147.3) in controls (Mann–Whitney U = 33.5, p = 0.0009, rank-biserial r(b) = 0.92), indicating a marked reduction in this neuroprotective protein in PD. This evidence concerns the gene SIRT1 and Parkinson disease.