Further multivariate regression analysis showed that the correlation between serum BDNF levels and IRLSSG-RS scores remained significant in either PD with RLS or controls with RLS group (t = −5.764, p < 0.001; Table 3; t = −2.968, p = 0.008; Table 4), while adjusting for potentially confounding demographics, including sex, age, education, and BMI. This evidence concerns the gene BDNF and Parkinson disease.