In Reply We appreciate the comments expressed by Darweesh and colleagues and by Macerollo and Chen concerning our article on time trends for Parkinson disease (PD) in Olmsted County, Minnesota.1 Both groups of authors challenged the attribution of the increasing trend in the incidence of PD to a declining trend in cigarette smoking over time. They also called for an international collaborative research effort to identify risk and protective factors for PD.
Rocca WA, Savica R, Grossardt BR. Trends in the Incidence of Parkinson Disease—Reply. JAMA Neurol. 2016;73(12):1498-1499. doi:10.1001/jamaneurol.2016.3847