Abstract
            Background: The long-term effects of childhood screen time on health-related quality of life (HRQoL) are still unclear. This study  aimed to investigate the relationship between screen time during adolescence and sex-specific HRQoL in early youth.  
  Methods: We studied the data from 642 adolescents aged 13-19 years, who participated in the Tehran Lipid and Glucose Study  from 2005 to 2011 (baseline) with complete data on HRQoL in their early adulthood (22-28 years at the last follow-up). Physical  and Mental HRQoL were assessed using the Iranian version of the short-form 12-item health survey version 2 (SF-12v2). Screen  time and leisure-time physical activity were evaluated using the Iranian Modifiable Activity Questionnaire (MAQ). All analyses  were conducted in Stata (version 14); MI used the mi impute command.  
  Results: The mean±SD of age, body mass index (BMI), and physical activity in childhood were 16.33±1.27, 23.27±4.63 and  13.77±16.07, respectively. Overall, 35% of boys and 34% of girls had high screen time (HST) in childhood. In general, the HRQoL  scores in male participants were higher than in females in both the mental and physical domains. HST in males in childhood  was associated with decreased mental health (β=-6.41, 95% CI: -11.52, -1.3 and P=0.014), social functioning (β=-5.9, 95% CI:  -11.23, -0.57 and P=0.03) and mental component summary (MCS) (β=-2.86, 95% CI: -5.26, -0.45 and P=0.02). The odds of poor  MCS were significantly higher in those with HST compared to their counterparts with low screen time (LST) after adjusting for all  potential cofounders.  
  Conclusion: The results of the present study showed the negative effect of screen time during adolescence on HRQoL in early  youth. This effect was observed in men, mainly in the mental dimension. Investigating the long-term consequences of screen-time  behaviors on self-assessed health in other populations with the aim of effective primary prevention is also suggested.