the impact of phone calls on follow-up rates in an online depression prevention study

Background: Automated Internet intervention studies have generally had large dropout rates for follow-up assessments. Live phone follow-ups have been often used to increase follow-up completion rates. Objective: To compare, via a randomized study, whether receiving phone calls improves follow-up rates beyond email reminders and financial incentives in a depression prevention study. Method: A sample of 95 participants (63 English-speakers and 32 Spanish-speakers) was recruited online to participate in a “Healthy Mood” study. Consented participants were randomized to either a Call or a No Call condition. All participants were sent up to three email reminders in one week at 1, 3, and 6 months after consent, and all participants received monetary incentives to complete the surveys. Those in the Call condition received up to ten follow-up phone calls if they did not complete the surveys in response to email reminders. Results: The follow-up rates for Call vs. No Call conditions at 1, 3, and 6 months, respectively, were as follows: English speakers, 58.6% vs. 52.9%, 62.1% vs. 52.9%, and 68.9% vs. 47.1%; Spanish speakers, 50.0% vs. 35.7%, 33.3% vs. 21.4%, and 33.3% vs. 7.1%. The number of participants who completed follow-up assessments only after being called at 1-, 3- and 6 months was 2 (14.3%), 0 (0%), and 3 (25.0%) for English speakers, and 2 (18.9%), 0 (0%), and 1 (7.7%) for Spanish speakers. The number of phone calls made to achieve one completed follow-up was 58.8 in the English sample and 57.7 and Spanish-speaking sample. Conclusions: Adding phone call contacts to email reminders and monetary incentives did increase follow-up rates. However, the rate of response to follow-up was low and the number of phone calls required to achieve one completed follow-up raises concerns about the utility of adding phone calls. We also discuss difficulties with using financial incentives and their implications.