1. From the Division of Pulmonary and Critical Care Medicine, School of Medicine;
2. Department of Epidemiology, School of Hygiene and Public Health;
3. Department of Health Policy and Management, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland;
4. Merck & Co, Inc, West Point, Pennsylvania; and
5. Division of General Medicine, School of Medicine, Johns Hopkins University, Baltimore, Maryland.