A new paper which comes to the opposite conclusion.

Pichler et al. report [1] that their:

"findings suggest that increased iron levels in the blood are associated with a 3% reduction in the risk of Parkinson disease for every 10 µg/dl increase in iron. This finding is important as it suggests that increased blood iron levels may have a protective effect against Parkinson disease, although the underlying mechanism remains unclear. Furthermore, although mendelian randomization is an increasingly used approach to address the issue of classical confounding, there may be remaining confounding factors specific of mendelian randomization that may influence the interpretation of this study."

Reference:

[1] Pichler I, Del Greco M. F, Gögele M, Lill CM, Bertram L, et al. (2013) Serum Iron Levels and the Risk of Parkinson Disease: A Mendelian Randomization Study. PLoS Med 10(6): e1001462. doi:10.1371/journal.pmed.1001462 Published: June 4, 2013
http://www.plosmedicine.org/article/...l.pmed.1001462

John