Funding for this research was provided by:
Chinese National Natural Science Foundation (81571234)
Shandong Province medical science and technology development projects (2014WS0260)
Yantai Science and Technology Development Project (2014WS035, 2016WS037)
Key research and development plan of Shandong Province (2018GSF118235)
Article History
Received: 20 February 2018
Accepted: 20 September 2018
First Online: 8 October 2018
Ethics approval and consent to participate
: The PPMI study was approved by the Institutional Review Boards of each PPMI site. Informed written consent was obtained from all subjects at each site.
: Not applicable
: The authors declare that they have no competing interests.