Bedtime smart device usage and accelerometer-measured sleep outcomes in children and adolescents

PURPOSE: We analyzed the association between bedtime smart device usage habits and accelerometer-measured sleep outcomes (total sleeping time, sleep efficiency, and wake after sleep onset) in Hong Kong children and adolescents aged 8–14. METHODS: A total of 467 students in Hong Kong participated in this study from 2016 to 2017. They self-reported their bedtime smart device usage habits. The primary caregiver of each participant was also invited to complete a self-administered questionnaire about the family’s social-economic status and bedtime smart device usage habits. An ActiGraph GT3X accelerometer was used to assess participants’ 7-day sleep outcomes. RESULTS: The mean age of the participants was 10.3 (SD 1.9), and 54% were girls. Among the participants, 27% (n = 139) used a smart device before sleep, and 33% (n = 170) kept the smart device on before sleep. In total, 27% (n = 128) placed the smart device within reach before sleep, 23% (n = 107) would wake up when notifications were received, and 25% (n = 117) immediately checked the device after being awakened by a notification. Multiple regression controlling for age, sex, socio-economic status, and other confounders showed that those who woke up after receiving a notification had a statistically longer sleeping time (19.7 min, 95% CI: 0.3, 39.1, p = 0.046), lower sleep efficiency (− 0.71%, 95% CI − 1.40, − 0.02, p = 0.04), and a longer wake after sleep onset (2.6 min, 95% CI: 0.1, 5.1, p = 0.045) than those who did not. Nonetheless, all primary caregivers’ bedtime smart device habits were insignificantly associated with all sleep outcomes of their children. CONCLUSION: Those who woke up after receiving smart device notifications had lower sleep efficiency and longer wake after sleep onset than those who did not, and they compensated for their sleep loss by lengthening their total sleep time. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11325-021-02377-1.