Postcards encourage participant updates

Participant retention is vital to the success of a longitudinal cohort study. Various approaches have been used for retaining participants in longitudinal studies, including maintaining up-to-date contact information. Postcards are sent to Millennium Cohort Study participants each Memorial and Veterans Day to honor their military service, thank them for their continued participation, and prompt them to update their contact information. Descriptive investigations of the Millennium Cohort Study participants who voluntarily updated their contact information online and had a change of address were completed. The percentage of participants who updated their contact information online of the total number of current participants was graphically displayed. Univariate analyses were completed to temporally compare the volume of updated contact information associated with Memorial and Veterans Day postcards. The results show that almost 77% of Cohort members moved between 2001 and 2007. Of these, 12% voluntarily updated their contact information online. Of those who updated their contact information online, 65% updated their contact information at least once within 2 weeks of semiannual postcard contact. Even in times of significant combat deployments, the U.S. military is a highly mobile population. Semiannual appreciatory contact is an effective way to maintain communication with study participants while prompting updates of contact information.