1. Department of Medicine, University of California, San Francisco , San Francisco, California , USA
2. Department of Medicine, San Francisco Veterans Affairs Health Care System , San Francisco, California , USA
3. Department of Medicine, University of Miami Miller School of Medicine , Miami, Florida , USA
4. Department of Medicine, University of North Carolina School of Medicine , Chapel Hill, North Carolina , USA
5. Department of Medicine, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania , USA
6. Department of Medicine, Albert Einstein College of Medicine , Bronx, New York , USA
7. Department of Epidemiology, Johns Hopkins University , Baltimore, Maryland , USA
8. Department of Medicine, Emory University School of Medicine , Atlanta, Georgia , USA