Associations between bedtime media use and sleep outcomes in an adult population-based cohort.

Objective: To further examine the relationship between bedtime media use and sleep in adults by taking relevant covariates into account and testing hypothesised mediating and moderating pathways.

Methods: Bedtime media use and sleep outcomes were examined by questionnaire in 4188 adults (59 % women, aged 19-94 years) from the Specchio cohort based in Geneva, Switzerland. We tested associations between bedtime media use and sleep (bedtimes, rise times, sleep latency, sleep duration, sleep quality, insomnia, and daytime sleepiness), adjusting for prior sleep, mental health, and health behaviours; whether bedtime media use mediates associations between individual susceptibility factors (age, chronotype, and mental health) and sleep; and whether individual susceptibility factors moderate associations between bedtime media use and sleep.

Results: Often using a screen in the 30 minutes before going to sleep at night was associated with a late bedtime (≥midnight; OR [95 % CI] = 1.90 [1.44,2.51], p < 0.001), a short sleep duration (<7 h; 1.21 [1.01,1.46], p < 0.05), and excessive daytime sleepiness (Epworth score >9; 1.47 [1.25,1.74], p < 0.001), adjusting for all covariates. Bedtime media use partly mediated the association between younger age and an evening chronotype and these sleep outcomes. Mental health moderated the association between bedtime media use and sleep quality/insomnia, such that the former was only associated with poorer sleep quality/insomnia among individuals with better mental health.

Conclusions: Frequent bedtime media use was associated with various sleep outcomes, independently of relevant covariates. Limiting the use of screens at bedtime is important to promote sleep among adults. Individuals with poorer mental health likely require additional support to improve their sleep quality.