Retaining school children and families in community research: lessons from the Study of Children's Activity and Nutrition (SCAN).

Retaining school-aged study participants poses a major challenge in any longitudinal research study. Dropouts produce bias in the remaining sample and this loss may affect study findings and their interpretation. Dominant factors that influence retention in pediatric research studies include family versus individual participation, patient management strategies of study personnel, knowledge about the condition or therapy, age and gender factors, credibility within the community, monetary incentives, and altruism. Eleven years after baseline assessment, Studies of Children's Activity and Nutrition boasts a 53% retention of the original biethnic cohort in San Diego. Retention occurred partly due to a trained measurement team which completed sequential observations primarily in family homes and implemented continuous participant follow-up procedures. Approaches for increasing student retention based on carefully designed studies and adherence indicators can assist researchers seeking maximum retention of school-aged participants.