1. Department of Medicine, University of California, San Francisco, San Francisco, California;
2. The College of Medicine, University of Arizona Health Sciences, Tucson, Arizona;
3. University of Vermont, Burlington, Vermont;
4. Johns Hopkins University, Baltimore, Maryland;
5. Department of Community Health and Epidemiology, Dalhousie University, Halifax, Nova Scotia, Canada; and
6. National Heart and Lung Institute, Imperial College London, London, United Kingdom