Genoud S, et al. - Researchers conducted a random-effects meta-analysis and meta-regression subgroup analysis to analyze changes in copper and iron levels in human Parkinson disease (PD) brain and biofluids. Literature databases were systematically searched for quantitative reports of biometal levels in the degenerating substantia nigra (SN), CSF, serum, and plasma in PD (n = 211) vs healthy age-matched controls (n = 215) and evaluated the quality of these publications. The authors discovered that SN copper levels were significantly lower and iron levels were significantly higher in PD in the 18 eligible studies identified. No changes for any metals (29 studies; 2,443 PD and 2,183 control cases) were detected in CSF, serum, or plasma except for serum iron, which was lower in PD (14 studies; 1,177 PD and 1,447 control cases). Reductions in copper levels and iron elevations were confirmed as a feature of PD's degenerating SN. Iron in serum has also been modified, but in the SN and to a lesser extent in the opposite direction.