1. University of Maryland School of Medicine , Baltimore, Maryland , USA
2. Department of Epidemiology and Public Health, University of Maryland School of Medicine , Baltimore, Maryland , USA
3. Medical Service, Veterans Affairs (VA) San Francisco Health Care System , San Francisco, California , USA
4. Department of Medicine, University of California San Francisco , San Francisco, California , USA
5. Division of General Internal Medicine, Memorial Sloan Kettering Cancer Center , New York, New York , USA
6. Medical Service, Veterans Affairs (VA) Maryland Health Care System , Baltimore, Maryland , USA