HMOX1 and Parkinson disease: There were no statistically significant differences in HO-1 levels among the three groups (early PD patients, advanced PD patients and healthy controls) in either men or women [male: 2.39 (2.11, 2.97) vs. 2.38 (2.02, 2.61) vs. 2.18 (1.70, 2.61) ng/ml, p = 0.176; female: 2.34 ± 0.60 vs. 2.10 ± 0.53 vs. 2.01 ± 0.41 ng/ml, p = 0.053; Supplementary Figure 1].