Funding for this research was provided by:
National Institute on Aging (P01AG041710, 3U54HG006938, 1R01AG051144)
Fogarty International Center (K43TW010698)
Wellcome Trust (58893/Z/99/A, 085477/B/08/Z, 069683/Z/02/Z)
Received: 14 July 2019
Accepted: 11 November 2019
First Online: 27 November 2019
Ethics approval and consent to participate
: The study received ethical approvals from the University of the Witwatersrand Human Research Ethics Committee (ref M141159), the Harvard T.H. Chan School of Public Health, Office of Human Research Administration (ref C13–1608-02), and the Mpumalanga Provincial Research and Ethics Committee (approved: 2014/10/22). Each respondent provided written, informed consent (or by a proxy, when needed).
: Not applicable.
: The authors declare that they have no competing interests.