Panel studies in developing countries: case analysis of sample attrition over the past 16 years within the birth to twenty cohort in Johannesburg, South Africa

The implementation of panel studies in developing countries can prove valuable in driving evidenced‐based policies. Case analysis from panel studies in developing countries are therefore useful in offering guidance and insight to deal with the immense challenges of implementing and following‐up a panel study in a developing country. The aim of this paper is to describe the follow‐up process within Birth to Twenty (Bt20), a birth cohort study in Johannesburg, South Africa, over the past 16 years; and to outline retention strategies and insight within the context of an urban, developing country setting. The main issues considered are: attrition (periodic and absolute), movement of individuals, name changes, cohort management and lessons learned.