1. VA Boston Healthcare System , Boston, Massachusetts, USA
2. Boston University School of Medicine , Boston, Massachusetts, USA
3. Yale School of Public Health , New Haven, Connecticut, USA
4. Yale School of Medicine , New Haven, Connecticut, USA
5. VA Connecticut Healthcare System , West Haven, Connecticut, USA
6. VA Central Western Massachusetts Healthcare System , Leeds, Massachusetts, USA
7. Department of Population and Quantitative Health Sciences, University of Massachusetts Medical School , Worcester, Massachusetts, USA