Increased bilirubin levels in de novo Parkinson's disease

Background and purpose Oxidative stress is a central pathogenic mechanism of Parkinson's disease (PD), and the heme oxygenase (HO) bilirubin pathway is one of the main mammalian antioxidative defences. Indeed, there is growing evidence of HO−bilirubin upregulation from early phases of PD. Our aim was to investigate bilirubin as a possible biomarker of PD diagnosis and progression. Methods A cross‐sectional case−control study was performed to evaluate differences in bilirubin levels between newly diagnosed, drug‐naïve PD subjects and controls. Afterwards, PD subjects were included in a 2‐year longitudinal study to evaluate disease progression in relation to baseline bilirubin levels. Results Seventy‐five de novo PD subjects were selected and matched with 75 controls by propensity score. Analysis of variance showed higher bilirubin levels in PD patients compared with controls (P