Commencement of and Retention in Web-Based Interventions and Response to Prompts and Reminders: Longitudinal Observational Study Based on Two Randomized Controlled Trials

Background Web-based interventions are effective for several psychological problems. However, recruitment, adherence, and missing data challenges when evaluating these interventions. Objective This study aimed to describe the use patterns during commencement phase, possible retention (continuation of provision), responses prompts reminders among participants in 2 randomized controlled trials (RCTs) web-based Methods Data on logged RCTs aiming reduce symptoms anxiety depression adult patients recently diagnosed with cancer (AdultCan RCT) a recent myocardial infarction (Heart were analyzed. The intervention AdultCan trial consisted unguided self-help psychoeducation that Heart therapist-supported cognitive behavioral therapy. In total, 2360 participants’ at first log-in, including collection baseline (ie, commencement) follow-ups, Both comparison groups Results At commencement, 70.85% (909/1283) 86.82% (935/1077) RCTs, respectively, completed after receiving welcome email log-in credentials. median duration was 44 minutes 38 respectively. Slightly less than half log-ins outside standard office hours. More 80% (92/114 103/111) both explored within weeks being treatment group, 7 47 There significant association between exploration time but not trial. control group most likely retain provide complete follow-up data. Across 3 points this study, proportion responding all questionnaires 1 week from prompt, without reminder, varied 35.45% (413/1165) 66.3% (112/169). After reminders, up 97.6% (165/169) responded. Conclusions Most email. Approximately them answered questions hours, suggesting flexibility inherent contributes use. contrast what expected, generally had lower completion rates groups. About thereafter, contributed retention, they effective. Strategies increase eHealth important future development relevant research.