[1] Univ Witwatersrand, Fac Hlth Sci, Sch Clin Med, Dept Internal Med,Hlth Econ & Epidemiol Res Off, Johannesburg, South Africa
[2] Harvard Univ, Sch Publ Hlth, Dept Global Hlth, 665 Huntington Ave, Boston, MA 02115 USA
[3] Harvard Univ, Sch Publ Hlth, Dept Epidemiol, 665 Huntington Ave, Boston, MA 02115 USA
[4] Columbia Univ, Dept Epidemiol, Mailman Sch Publ Hlth, New York, NY USA
[5] Univ Witwatersrand, Dept Internal Med, Fac Hlth Sci, Johannesburg, South Africa
[6] Boston Univ, Boston, MA 02215 USA
[7] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Mental Hlth, Baltimore, MD USA