Postcards Encourage Participant Updates

Abstract

To the Editor: Participant retention is vital to the success of a longitudinal cohort study. Investigators may attempt to bolster retention rates by developing techniques to maintain up-to-date contact information, and foster participants’ perception of the importance of the research and their dedication to the study.1 Studies have used various approaches to retain cohort participants, including mailing reminders through the US Postal Service tracking programs, providing incentives for participation, maintaining open communication via a study web site or toll-free phone line, and telephone reminders.2–4 Maintenance of reliable address information in mobile populations3,5 may require contacting participants at regular time intervals.4 Previous studies have shown that sending postcards to participants is an effective method of retention. Regular contact not only develops participant identification with the cohort, but also encourages participants to update any changes to their contact information.4 The Millennium Cohort Study was designed in the late 1990s in response to US Department of Defense, Congressional, and Institute of Medicine recommendations for coordinated epidemiologic research to determine how military service affects long-term health.6,7 Launched in 2001, this 22-year longitudinal study surveys participants every 3 years, and a postcard and an electronic mail message are sent to cohort members on Memorial and Veterans day to honor their military service, and to thank them for their continued participation in the study. Members are reminded of the web site where they may obtain information on study progress and findings, contact the study team, and update their contact information (mailing address, e-mail address, phone number, or name). Specially designed postcards with the study logo and personal signature of the principal investigator provide study recognition and encourage a sense of membership in the cohort. The purpose of this study was to determine whether semiannual e-mails and postcards encourage participants to update their contact information. Approximately 77% of the nearly 108,000 military service members in the current analysis have moved after enrollment in the cohort, of whom two-thirds moved to a different state or country. Of those who moved, 9% went online to change their address. Participants who updated their contact information online were more likely to be women, older, college educated, and officers. The great majority (65%) of those who updated their contact information did so within 2 weeks after receipt of the semiannual postcards (Fig. 1). Participants were much more likely to update their contact information during the 2 weeks after (average = 1.09%) receipt of the semiannual postcards than during the 2 weeks before (average = 0.03%).FIGURE 1.: Weekly percentage of all participants who updated their contact information on the Millennium Cohort web site, November 2002 to March 2007. Asterisks (*) indicate when postcards were mailed to participants.The results of this study quantify and confirm that semiannual postcard contact with participants produces a significant increase in the number of persons who update their contact information online compared with the baseline rate when no contact is attempted. In addition, contacting participants on a consistent basis with a personalized message seems to encourage a sense of connectivity with participants and reminds them of the value of their participation. Kari E. Welch Cynthia A. LeardMann Isabel G. Jacobson Steven J. Speigle Besa Smith Tyler C. Smith Margaret A. Ryan Department of Defense Center for Deployment Health Research Naval Health Research Center San Diego, CA