1. Department of Biostatistics; Brown University; Providence RI U.S.A.
2. Department of Health Services, Policy and Practice; Brown University; Providence RI U.S.A.
3. Departments of Emergency Medicine and Epidemiology; The Warren Alpert School of Medicine of Brown University, Rhode Island Hospital; Providence RI U.S.A.
4. The Warren Alpert School of Medicine of Brown University, The Miriam Hospital; Providence RI U.S.A.