Submitted for Publication: August 13, 2013; final revision received October 25, 2013; accepted November 1, 2013.
Published Online: December 26, 2013. doi:10.1001/jamaoto.2013.6149.
Study concept and design: Kwon, Roh, Nam.
Acquisition of data: Kwon, Lee, Roh, Cho, Choe, Choi, Nam.
Analysis and interpretation of data: Kwon, Roh, Kim.
Drafting of the manuscript: Kwon, Lee, Roh, Choe, Choi, Nam, Kim.
Critical revision of the manuscript for important intellectual content: Kwon, Roh, Cho.
Statistical analysis: Kwon, Lee, Roh.
Administrative, technical, or material support: Roh, Cho, Choi, Nam.
Study supervision: Roh, Nam, Kim.
Conflict of Interest Disclosures: None reported.