Author Contributions: Dr J. Sundquist had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Crump, K. Sundquist, J. Sundquist, Winkleby.
Acquisition of data: J. Sundquist.
Analysis and interpretation of data: Crump, K. Sundquist, J. Sundquist, Winkleby.
Drafting of the manuscript: Crump, Winkleby.
Critical revision of the manuscript for important intellectual content: Crump, K. Sundquist, J. Sundquist, Winkleby.
Statistical analysis: Crump, J. Sundquist, Winkleby.
Obtained funding: K. Sundquist, J. Sundquist.
Administrative, technical, or material support: J. Sundquist.
Study supervision: J. Sundquist, Winkleby.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
Funding/Support: This study was supported by grants from the National Institute of Child Health and Human Development (1R01HD052848-01), the Swedish Research Council (2008-3110 and 2008-2638), the Swedish Council for Working Life and Social Research (2006-0386, 2007-1754, and 2007-1962), and an ALF project grant (Avtal om Läkarutbildning och Forskning, or Agreement on Medical Training and Research), Lund, Sweden.
Role of the Sponsors: The funding agencies had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, or approval of the manuscript.