Background: Using the multiphase optimization strategy (MOST) framework, we aimed to identify a feasible, acceptable and optimized set of mHealth-delivered behavioral strategies for reducing recreational sedentary screen time (rSST) by at least 60 min/day.
Methods: Eligible participants were 23-64 years old and had high rSST (> 3 h/day). We used a full factorial (23) design in which participants received a "core" mHealth application and were randomized to combinations of three components (on vs. off): LOCKOUT: rSST electronically restricted; TEXT: rSST reduction prompts; and EARN: rSST through physical activity. rSST was assessed at baseline and at 8 and 16 weeks of age via an integrated measure of sedentary time and screen time. We used a linear mixed effect model to test the change in rSST for the three intervention components and their interactions.
Results: A total of 82% of the randomized participants (N = 110) were female, with a mean ± SD age of 41 ± 11.7 y and a BMI of 29.7 ± 7.8 kg/m2, and their mean (95% CI) rSST was 184.7 (172.8, 196.5) min/day at baseline. The expected difference (baseline vs 16 weeks) in rSST was greatest for the intervention versions with a core, LOCKOUT, TEXT, & EARN (-125.7 [-172.0, -79.3] min/day) at the "on" level. The participants were satisfied with the study and found the app helpful in reducing rSST (> 94%). Technical issues resulted in 20% being somewhat dissatisfied with the app.
Conclusions: We identified several promising intervention versions that exceeded our optimization objective. The intervention version that included core, LOCKOUT, TEXT, & EARN components "on" was efficacious, feasible and acceptable and should be used to test the effect of rSST reductions on health outcomes.
Trial registration: (clinicaltrials.gov NCT04464993).
Keywords: mHealth application; multiphase optimization trial; physical activity; screen time; sedentary behavior; television viewing.