Accepted for Publication: March 23, 2015.
Published Online: June 15, 2015. doi:10.1001/jamaneurol.2015.0703.
Study concept and design: Fereshtehnejad, Gagnon, Postuma.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Fereshtehnejad.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Fereshtehnejad, Anang.
Obtained funding: Fereshtehnejad, Gagnon, Postuma.
Administrative, technical, or material support: Anang, Latreille.
Study supervision: Postuma.
Conflict of Interest Disclosures: Dr Postuma received personal compensation for travel and speaker fees from Novartis Canada, Biotie, and Teva Neurosciences and is funded by grants from the Fonds de Recherche du Québec–Santé, the Parkinson Society of Canada, the Webster Foundation, the W. Garfield Weston Foundation, and the Canadian Institutes of Health Research. Dr Gagnon is funded by grants from the Fonds de Recherche du Québec–Santé, the W. Garfield Weston Foundation, and the Canadian Institutes of Health Research. Drs Anang and Romenets have received research funding from the Parkinson Society of Canada. No other disclosures were reported.
Funding/Support: This study was supported by the Fonds de Recherche du Québec–Santé and the Canadian Institute of Health Research and, in part, by a Parkinson’s Disease Foundation Summer Student Fellowship (PDF-SFW-1472) given to Dr Fereshtehnejad.
Role of the Funder/Sponsor: The sponsors had no role in the design and conduct of the study; collection, management, analysis, or interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Information: Dr Gagnon holds a Canada Research Chair on Cognitive Decline in Pathological Aging.
Additional Contributions: We would like to thank Michel Panisset, MD, and Sylvain Chouinard, MD, at Hôpital Notre-Dame du CHUM, Montréal, Québec, Canada, for helping us gather the clinical data in the movement disorder clinics. No funding was involved in their contributions.