[1] Univ Calif San Diego, Sch Med, Dept Family & Prevent Med, San Diego, CA 92093 USA
[2] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Epidemiol, Baltimore, MD 21205 USA
[3] Johns Hopkins Univ, Sch Med, Dept Med, Baltimore, MD 21205 USA
[4] Univ Sydney, George Inst Global Hlth, Sydney, NSW 2000, Australia
[5] Univ Oxford, Nuffield Dept Populat Hlth, George Inst Global Hlth, Oxford OX3 7LF, England