Assessing the relationship between smartphone use and sleep in Swiss adolescents: A cohort study

Abstract Smartphone use is ubiquitous in adolescents’ daily lives and has been linked to poorer mental well-being, though the underlying mechanisms remain unclear. Sleep may serve as a mediator, as sleep deprivation and poor sleep quality are known to affect mental well-being. This study investigates the relationship between smartphone use and sleep among adolescents. Data is drawn from the ongoing HERMES (Health Effects Related to Mobile phone usE in adolescentS) cohort. The study includes 292 Swiss adolescents aged 11-15 years who completed electronic questionnaires on device use (e.g. typical daily screen time, device use before bedtime) and sleep habits (i.e. duration and the Sleep Disturbance Scale for Children (SDSC)). Linear mixed-effects models, clustered by school and adjusted for age, sex, and school level, were used to assess associations. Participants had a mean age of 13.5 years; 54.5% identifying as female. Most (92%) owned a smartphone, reporting an average of 138 minutes of daily screen time. Additionally, 64.7% used electronic devices within three hours of bedtime on four or more days per week. The mean SDSC score for disorders of excessive somnolence was 12.6 (ranging from 0-25). In a preliminary analysis, each additional hour of smartphone screen time was significantly associated with a 6-minute decrease in sleep duration on weekdays (95% CI: -11.8 to -0.26 min) but not on weekends (4.83 min; 95% CI: -12.39 to 2.73 min). Screen time was further associated with increased sleep disturbances, including a 0.74-point rise in somnolence (95% CI: 0.41 to 1.07), 0.10 in nightmares (95% CI: 0.01 to 0.2) and 0.48 in initiating and maintaining sleep (95% CI: 0.16 to 0.79) per hour of screen time. Preliminary findings indicate that higher smartphone use is linked to shorter sleep duration and increased sleep disturbances in adolescents. These findings highlight the importance of addressing smartphone use in youth to promote healthy sleep and mental well-being. Key messages • This study provides preliminary evidence that higher smartphone use among adolescents is associated with shorter sleep duration and increased sleep disturbances, particularly on weekdays. • Public health interventions aiming to improve adolescent mental health should consider integrating guidance on healthy digital behaviors and sleep.