Submitted for Publication: September 23, 2012; final revision received May 14, 2013; accepted November 7, 2013.
Published Online: January 2, 2014. doi:10.1001/jamaoto.2013.6207.
Study concept and design: All authors.
Acquisition of data: All authors.
Analysis and interpretation of data: All authors.
Drafting of the manuscript: All authors.
Critical revision of the manuscript for important intellectual content: All authors.
Administrative, technical, or material support: Ko, Kim, Shim.
Study supervision: Shim.
Conflict of Interest Disclosures: None reported.