Published Online: March 2, 2009 (doi:10.1001/jama.2009.265).
Author Contributions: Dr Wang 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: Wang, Tobler, Eick.
Acquisition of data: Wang.
Analysis and interpretation of data: Wang, Roayaei, Eick.
Drafting of the manuscript: Wang.
Critical revision of the manuscript for important intellectual content: Wang, Tobler, Roayaei, Eick.
Statistical analysis: Wang, Roayaei.
Study supervision: Tobler, Eick.
Financial Disclosures: None reported.
Disclaimer: The views expressed in this article are solely those of the authors and do not reflect the official policy or position of the Department of the Army, Department of Defense, or US government.
Additional Contributions: John F. Brundage, MD, MPH, Armed Forces Health Surveillance Center, and Joel Gaydos, MD, MPH, Armed Forces Health Surveillance Center, provided critique and review of the manuscript. Mike Patetta, MS, SAS Institute, and Zheng Hu, MS, Armed Forces Health Surveillance Center, provided technical assistance. None received compensation for the contributions.