Recreational screen media use and its effect on physical activity, sleep, and mental health in families with children

IntroductionThe availability and use of screen media devices have increased over the past decades. The screen media environment has changed, and it is important to understand today's screen media habits, the factors that determine children's screen media use in particular, and the potential consequences. Several organizations and health authorities recommend limiting, especially children's recreational screen media use. However, these recommendations are mainly based on low-certainty evidence of the harmfulinfluence of screen media use on health outcomes. Although several studies have reported negative relationships between screen media use and physical and mental health outcomes, these studies are mostly observational. Several limitations, such as reverse causation bias, residual confounding, and use of self-reported screen media use, limit the confidence in the results. Considering the limitations of previous studies, more carefully designed experimental research is needed to investigate whether the relationships between screen media use and health indicators are causal. AimThe overall aim of this thesis is to describe recreational screen media use among Danish school-aged children and explore the role of parental education, family structure, and household screen media rules,and investigate the effects of limiting recreational screen media use on physical activity, sleep, mental health, and biomarkers of stress in families with children.MethodsPaper I of the thesis is based on a cross-sectional study where 5,274 parents completed a digital population-based survey on screen media habits on behalf of themselves and one child in their household aged 6-11 years. The survey consisted of the recently developed SCREENS Questionnaires and several background questions. We used descriptive statistics to describe children's media habits.Multivariable logistic and linear regression was used to investigate cross-sectional associations between parental education, family structure, household screen media rules, and children’s screen media habits.Papers II and III are based on data collected in the SCREENS cluster randomized controlled trial. The trial was designed as an efficacy trial in free-living with careful assessment of intervention compliance.Families were recruited into the trial based on data the population-based survey. Eighty-nine families(181 children and 164 adults) participated in the trial. After completing the baseline measurement protocol lasting seven consecutive days, the participating families were randomized (1:1) to a two-week recreational screen media reduction intervention or screen media use as usual (control group). The protocol included the assessment of physical activity using waist and thigh worn accelerometers. Sleep was measured using single-channel electroencephalography in both children and adults. Additionally,the adults collected salivary samples and answered questionnaires on mental well-being and mood. The protocol was repeated during the last week of the two-week experiment. The primary outcome was the children's non-sedentary activity during leisure. We objectively assessed recreational screen media use using tracker software and TV monitors. The effect of the intervention was investigated using mixed effects models to account for the cluster structure of the data. ResultsThe descriptive results of Paper I showed that children's recreational screen media use and content varied by sex, age, and day type. Also, the children's ownership of screen devices increases markedly with age. The associative findings suggest that the children of parents with lower educational levels have higher odds of problematic screen media habits. The presence of household screen media rules was associated with less recreational screen media use in children.The primary experimental findings from Paper II were that the screen media reduction intervention significantly increased children's non-sedentary activity (between-group mean difference of 45min/day) and moderate to vigorous physical activity (between-group mean difference of 7.5 min/day). However, no significant findings were observed for physical activity in adults. Additionally, the results suggest that the screen media reduction intervention did not affect children's sleep parameters, while adults' sleep duration results were inconclusive. The results of Paper III showed that the adults' self-reported mental well-being and mood improved significantly compared to adults in the control group.However, no effects were observed on salivary biomarkers of stress (cortisol and cortisone).ConclusionsOverall, the findings of this thesis suggest that school-aged children spend large amounts of their leisure time using screen media devices for recreational purposes, with significant socio-economic disparity. Children living in families where household screen media rules are set spend considerably less time on recreational screen media use. Furthermore, the thesis provided evidence that reducing recreational screen media use is causally related to increased physical activity in children and improved mental health in adults. Collectively, the findings of this thesis warrant attention to the positive impacts of spending lower amounts of time on recreational screen media use. In a greater perspective,decreasing recreational screen media use in families could possibly prevent cases of physical and mental illness through decreased physical inactivity in children and improved mental health in adults. However,future studies should investigate if the observed effects of reducing recreational screen media use are evident in the long term. However, such studies should develop and evaluate more pragmatic screen restriction interventions.