Add to this the frame of the screen; for the screen is the standard by which we measure screen time, which is no more than increments of the present.
These items have been used to measure screen time among adolescents from several countries [ 6, 8] including Brazil [ 7, 36].
The same question, with proven acceptable reliability in this age group, was used to measure screen time activity exposure at both time points.
Third, some studies measured screen time separately on weekdays and weekend days [ 15, 16] although not all studies were clear about this aspect of the exposure assessment.
Because the question or questions used to measure screen time constitute a critical aspect of the prospective studies, it is interesting to note that all prospective studies to date differ in their assessment of screen time.
Also the measures of screen time used may be not representative of the broader time spent in sedentary activities [ 32].
It offers another useful measure of screen time – excluding TV – per day compared to school year and shows this increasing with age.
This protocol, with some modifications to outcome measures, screening procedures, time span, and inclusion criterion, can be extended to a fully-powered trial.
Although interesting, findings in the current study are subject to several limitations, including the use of self-report measures of MVPA, screen time and BMI.
In addition, since it is not feasible to obtain direct measurements of screen time in large population-based studies, the screen time measures were parental-reported.
