Introduction
HIV infections
HIV INFECTIONS
In 2021, there were 38.4 million people living with HIV (PLHIV) globally, most of whom (20.6 million, 54%) were in Eastern and Southern Africa with 1.5 million new HIV infections globally [Participant retention outcomes vary across different types of longitudinal studies. Very high rates of loss to follow-up are routinely reported in observational cohort studies, commonly conducted within public health settings. For example, antiretroviral treatment (ART) cohort studies measuring programmatic outcomes in Africa report attrition rates of up to 50% at 1 year [Research into reasons for poor retention in longitudinal studies has focused primarily on cohort studies and RCTs with few data from CRTs. Factors influencing retention in longitudinal studies may be considered at the levels of participant characteristics and contextual factors. Participant characteristics associated with higher attrition include being male [There remains a paucity of conclusive data on factors contributing to and effective strategies toward retention in longitudinal studies, not least from CRTs in high burden settings. In this study, we aimed to evaluate the association between baseline characteristics and retention of research participants in the PopART population cohort (PC), implemented in urban and peri-urban communities in Zambia and South Africa.