Screens, Teens, and Sleep: Is the Impact of Nighttime Screen Use on Sleep Driven by Physiological Arousal?

Few studies have objectively measured both screens and sleep in real-world settings. This study uses repeated measures to assess heart rate during evening screen use, providing new insights into how these behaviours relate to adolescent sleep. Screen use was recorded using wearable cameras over four nights in 70 youth (37% indigenous Māori, 42% female) aged 11-14.9 years. Heart rate was measured via a Fitbit Inspire 2. Mixed effects regression models were used to estimate within-person differences in heart rate across screen behaviours and time periods, as well as associations with sleep outcomes. Median heart rate was lower during screen use than during non-screen activities (83 BPM, [IQR: 77-91] vs. 93 [IQR: 87-100]). Social media use most proximal to bedtime was associated with slightly lower heart rate compared to other screen activities (-3 BPM, 95% CI: -5, -1), while communication was associated with slightly higher heart rate (3 BPM, 95% CI: 1, 5). Heart rate in the 2 h before bed was not associated with sleep outcomes except for sleep latency; which increased by 9 min (95% CI: 3, 14) for every 10 BPM increase in heart rate. Evening screen use may be a relaxation tool for youth, with social media, gaming and multitasking having minimal physiological impact. In contrast, communication activities were less conducive to relaxation, though differences were small and effects on sleep only modest. Thus, relationships between screen use and sleep are more likely driven by changes in sleep timing rather than physiological arousal from screen exposure. Trial Registration: Australian and New Zealand Clinical Trials Registry: ACTRN12621000193875.