School-based intervention on healthy behaviour among Ecuadorian adolescents: effect of a cluster-randomized controlled trial on screen-time

Background: Effective interventions on screen-time behaviours (television, video games and computer time) are needed to prevent non-communicable diseases in low-and middle-income countries. The present manuscript investigates the effect of a school-based health promotion intervention on screen-time behaviour among 12- to 15-year-old adolescents. We report the effect of the trial on screen-time after two stages of implementation. Methods: We performed a cluster-randomised pair matched trial in urban schools in Cuenca-Ecuador. Participants were adolescents of grade eight and nine (mean age 12.8 +/- 0.8 years, n = 1370, control group n = 684) from 20 schools (control group n = 10). The intervention included an individual and environmental component tailored to the local context and resources. The first intervention stage focused on diet, physical activity and screen-time behaviour, while the second stage focused only on diet and physical activity. Screen-time behaviours, primary outcome, were assessed at baseline, after the first (18 months) and second stage (28 months). Mixed linear models were used to analyse the data. Results: After the first stage (data from n = 1224 adolescents; control group n = 608), the intervention group had a lower increase in TV-time on a week day (beta = -15.7 min; P = 0.003) and weekend day (beta = -18.9 min; P = 0.005), in total screen-time on a weekday (beta = -25.9 min; P = 0.03) and in the proportion of adolescents that did not meet the screen-time recommendation (beta = -4 percentage point; P = 0.01), compared to the control group. After the second stage (data from n = 1078 adolescents; control group n = 531), the TV-time on a weekday (beta = 13.1 min; P=0.02), and total screen-time on a weekday (beta = 21.4 min; P = 0.03) increased more in adolescents from the intervention group. No adverse effects were reported. Discussion and Conclusion: A multicomponent school-based intervention was only able to mitigate the increase in adolescents' television time and total screen-time after the first stage of the intervention or in other words, when the intervention included specific components or activities that focused on reducing screen-time. After the second stage of the intervention, which only included components and activities related to improve healthy diet and physical activity and not to decrease the screen-time, the adolescents increased their screen-time again. Our findings might imply that reducing screen-time is only possible when the intervention focuses specifically on reducing screen-time.