An RCT Comparing Reminders Sendt by SMS or by E-mail in an Online Smoking Cessation Intervention

Web- and mobile phone health behavior change interventions, including smoking cessation programs, offer great promise, but little is known about how such interventions should be designed to increase user engagement. The primary purpose of the current study is to compare the effect of SMS-textmessage vs e-mail reminders on user engagement and proportion of reported quit attempts in an online smoking cessation intervention.

The investigators propose a 2-arm RCT with 700 adult study participants that all receive a best practices web-based smoking cessation program designed for use on smart phones (web-app). The intervention includes a ten day preparation phase, in which participants continue smoking. On the eleventh day (and onward) the user will receive a session in which (s)he is asked whether (s)he has quit smoking or not. If not, the user will receive additional treatment sessions until (s)he reports having quit (or dropped out of the study). Each day (for up to 14 days) a new unique session is assigned to the user. However, if the user does not log on to the web-intervention and starts using the session by noon on the second day after assignment, the user will receive a reminder to do so. When a user is to be sent a reminder for the first time, (s)he will be randomized to either receive such reminders by SMS or by e-mail.

The primary outcome is reporting a quit attempt or not. Secondary outcomes include number web-sessions started and completed and time spent navigating sessions after the first reminder is received.