1. Department of Epidemiology, University of Iowa College of Public Health, Iowa City, Iowa, USA
2. Division of Epidemiology, University of Utah School of Medicine, Salt Lake City, Utah, USA
3. Veterans Affair Salt Lake City Health Care System, Salt Lake City, Utah, USA
4. Iowa City Veterans Affair Health Care System, Iowa City, Iowa, USA
5. Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
6. Department of Biostatistics, University of Iowa College of Public Health, Iowa City, Iowa, USA
7. Mayo Clinic College of Medicine and Science, Rochester, Minnesota, USA