Author Contributions: Dr Bravata 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: Bravata, Smith-Spangler, Sundaram, Sirard.
Acquisition of data: Bravata, Smith-Spangler, Sundaram, Gienger, Lin, Lewis, Stave, Sirard.
Analysis and interpretation of data: Bravata, Smith-Spangler, Gienger, Lin, Olkin, Sirard.
Drafting of the manuscript: Bravata, Smith-Spangler, Sirard.
Critical revision of the manuscript for important intellectual content: Bravata, Smith-Spangler, Sundaram, Gienger, Lin, Lewis, Stave, Olkin, Sirard.
Statistical analysis: Bravata, Olkin.
Obtained funding: Bravata.
Administrative, technical, or material support: Bravata, Smith-Spangler, Sundaram, Gienger, Lin, Lewis, Sirard.
Study supervision: Bravata, Sirard.
Library searches: Stave.
Financial Disclosures: None reported.
Funding/Support: This project was supported by grant AG017253-06 from the National Institute on Aging through The Stanford Center on the Demography and Economics of Health and Aging. Dr Olkin was funded in part by grant DMS 9626265 from the National Science Foundation.
Role of the Sponsor: The funding agencies had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of this manuscript.
Acknowledgment: We thank Dawn Bravata, MD, Indiana University School of Medicine, for her thoughtful comments on a prior draft of the manuscript, for which she received no compensation.