IL6 and Parkinson disease: In the bivariate Pearson’s correlation analysis performed in the total sample, the PD-CRS total score was negatively associated in an almost negligible range with the levels of Il2 (r = − 0.146; p < 0.05), Il6 (r = − 0.178; p < 0.05), homocysteine (r = − 0.172; p < 0.05) and iron (r = − 0.171; p < 0.05).