COMMON ISSUES IN RETENTION
Unfortunately, enrolling participants into a study is not the end of the story; once participants are enrolled, strategies are needed to ensure that they will remain in the study. As noted, retention of participants is often challenging, especially in longitudinal studies. Common issues with retention include participant death, changes in location or residence, illness or other changes in status such as increased job or caregiving responsibilities. Participants may also lose interest in a project or become dissatisfied if the study does not meet their expectations. They may also decide not to participate if they are unhappy with their group assignment following randomization. Study design factors such as time demands, requirements of the intervention, or burdensome assessment protocols can also contribute to high rates of attrition. Overcoming these challenges takes careful planning and concerted effort on the part of the investigative team. In the following section, we discuss some strategies for alleviating problems with recruitment and participant retention.