Factors encouraging cohort maintenance in a longitudinal study.

Maintenance of the cohort is one of the primary challenges of a longitudinal study. At the end of 3 years of follow up in the Framingham Children's Study, a longitudinal study of young children and their parents, 100 of the original 106 families (94.3%) have remained in the study. A questionnaire was administered to identify factors contributing to the high rate of follow up to this point in the study. The attitudes of the staff, feedback to the subjects, the staff's handling of questions and problems, and association with the Framingham Heart Study emerged as the most important factors influencing continued participation in the study. In addition, 99% of the subjects stated that they believed the medical research to be important. We conclude that the quality of the communication with study participants and the subjects' perceived importance of the research have been the key factors in maintaining the cohort in this longitudinal epidemiologic study.