Accepted for Publication: June 20, 2014.
Published Online: October 6, 2014. doi:10.1001/jamainternmed.2014.5214.
Study concept and design: J. Wang, Xiao.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: J. Wang, Xiao.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: J. Wang, Zheng.
Obtained funding: Xiao.
Administrative, technical, or material support: J. Wang, P. Wang, X. Wang, Xiao.
Study supervision: Xiao.
Conflict of Interest Disclosures: None reported.
Funding/Support: Dr Xiao was supported by a grant (2013ZX10004217) from National Mega Project of Science and Technology, China.
Role of the Sponsor: The funder had no role in the design and conduct of the study; the collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Contributions: The authors are grateful to all members of the investigational team who collected the data. We also thank all investigated institutions for providing information and assistance during the study.