Supplemental Digital Content is available in the text.
Stanford Prevention Research Center, Department of Medicine, Stanford University School of Medicine, Stanford, CA email@example.com
Division of Epidemiology and Division of Social and Behavioral Sciences, Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada
Supported by the Stanford Department of Medicine.
The authors report no conflicts of interest.
Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article (www.epidem.com). This content is not peer-reviewed or copy-edited; it is the sole responsibility of the author.