Movement behaviors, sleep, and screen time in middle childhood: A 24-hour framework analysis
New research from Portuguese investigators reveals how sedentary time, sleep efficiency, and sex independently predict high screen time exposure in children, supporting calls for integrated 24-hour movement guidelines in public health.
Published June 28 in Human Movement Science, the study examined 307 children aged 6 to 10 years (mean age 8.5) from the Evora region of Portugal. Using wrist-worn accelerometers for seven consecutive days, researchers captured objective measurements of sedentary time, moderate-to-vigorous physical activity (MVPA), sleep duration, and sleep efficiency. Screen time was collected through parent-reported questionnaires and analyzed across three categories: low, moderate, and high exposure.
What they found
After adjusting for age, sex, body mass index, waist circumference, and motor competence, three factors emerged as significant independent predictors of high screen time.
Higher sedentary time was positively associated with high screen time (odds ratio 1.13, p = 0.02), meaning that for each unit increase in daily sedentary minutes, the likelihood of belonging to the high screen time category rose by 13 percent. Longer total sleep time showed a small but significant protective effect (OR 0.99, p = 0.03), with each additional minute of sleep slightly reducing the odds of high screen use. Sleep efficiency, or the proportion of time in bed actually spent asleep, was positively associated with high screen time (OR 1.07, p = 0.01), suggesting that children with the most consolidated sleep may paradoxically be those with the highest screen exposure.
Sex was a strong predictor. Girls had 59 percent lower odds of being in the high screen time category compared with boys (OR 0.41, p = 0.002), a finding the authors describe as robust across all models tested.
No significant independent associations were found between high screen time and MVPA, BMI, waist circumference, or motor competence. This is a notable null result: physical activity volume alone did not differentiate children with low versus high screen exposure once other movement behaviors were accounted for.
Why it matters
These findings lend support to the 24-hour movement behavior framework, an emerging paradigm in pediatric health that considers the full spectrum of movement across the day rather than isolating physical activity, sedentary behavior, or sleep. The data suggest that screen time in middle childhood is embedded within a broader behavioral ecology: children with high screen time are more sedentary overall, sleep slightly less, yet may have more efficient sleep possibly due to greater accumulated sleep pressure.
The strong sex difference points to a need for sex-sensitive intervention strategies. Boys in this sample were at markedly higher risk for high screen exposure, and the authors argue that interventions targeting after-school routines and media environments should account for these differences rather than applying a one-size-fits-all approach.
The absence of a link between MVPA and screen time also carries implications. It suggests that simply promoting physical activity may not be sufficient to reduce screen time. Behavior change strategies may need to directly target sedentary time and the contexts in which screen use occurs, particularly during unstructured after-school hours.
Limits
As a cross-sectional study, the analysis cannot establish causality or direction. It remains unclear whether high screen time drives greater sedentary behavior and shorter sleep, or whether children who are already more sedentary and sleep less naturally gravitate toward screens. All participants were recruited from a single region in Portugal, limiting generalizability to other populations. Screen time was parent-reported and may be subject to recall bias or social desirability effects. The sample was relatively homogeneous, and the study did not assess screen content or the timing of screen use relative to bedtime, both of which may influence sleep outcomes.
Bottom line
Screen time in middle childhood is independently associated with higher sedentary time and lower total sleep time, and boys appear to be at significantly greater risk than girls. The findings strengthen the case for public health interventions that treat movement behaviors as interconnected rather than isolated and that tailor strategies by sex and the contexts in which screen use accumulates.