1. Warren Alpert Medical School, Brown University, Providence, RI, USA
2. Department of Behavioral and Social Sciences, School of Public Health, Brown University, Providence, RI, USA
3. Population Studies and Training Center, Brown University, Providence, RI, USA
4. Division of Social and Behavioural Sciences, School of Public Health and Family Medicine, University of Cape Town, Cape Town, South Africa
5. Department of Public Health Sciences, University of Virginia, Charlottesville, VA, USA
6. Department of Epidemiology, School of Public Health, Brown University, Providence, RI, USA
7. Department of Sociology, Brown University, Providence, RI, USA