Author Contributions: Dr Hoge and Ms Auchterlonie had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Hoge, Auchterlonie, Milliken.
Acquisition of data: Auchterlonie.
Analysis and interpretation of data: Hoge, Auchterlonie, Milliken.
Drafting of the manuscript: Hoge, Auchterlonie, Milliken.
Critical revision of the manuscript for important intellectual content: Hoge, Auchterlonie, Milliken.
Statistical analysis: Hoge, Auchterlonie.
Obtained funding: Hoge.
Administrative, technical, or material support: Hoge, Auchterlonie.
Study supervision: Hoge, Milliken.
Financial Disclosures: None reported.
Funding/Support: This research was funded by an intramural program of the US Army Medical Research and Materiel Command, Ft Detrick, Md.
Role of the Sponsor: The funding organization reviewed and approved the manuscript but had no role in design and conduct of the study; collection, management, analysis, or interpretation of the data; or preparation of the manuscript.
Disclaimer: The views expressed in this article are those of the authors and do not reflect official policy or position of the Department of the Army, the Department of Defense, the US Government, or any of the institutional affiliations listed.
Acknowledgement: We thank the following individuals for their many suggestions on this project and their review of the manuscript: John Brundage, MD, MPH, Army Medical Surveillance Activity, US Army Center for Health Promotion, and Preventive Medicine; Carl Castro, PhD, Walter Reed Army Institute of Research, Washington, DC; and Charles C. Engel, MD, MPH, Walter Reed Army Medical Center and Uniformed Services University of Health Sciences, Bethesda, Md.