1. VA Cooperative Studies Program Coordinating Center, VA Boston Healthcare System, Boston, MA, USA
2. Department of Medicine, Boston University Chobanian and Avedisian School of Medicine, Boston, MA, USA
3. Department of Biostatistics, Boston University School of Public Health, Boston, MA, USA
4. Department of Preventive Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
5. Minneapolis VA Health Care System, Minneapolis, MN, USA
6. Department of Medicine, University of Minnesota, Minneapolis, MN, USA