Bedtime electronic device use and sleep quality in Chinese young adults: a longitudinal study

The proliferating use of electronic devices among young adults has raised growing concerns about their potential adverse effects on sleep quality. However, longitudinal evidence remains limited, particularly within Chinese student populations. This prospective 5-year longitudinal study enrolled 1,057 medical students from the China Undergraduate Cohort (CUC) spanning 2019 to 2024. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), while bedtime electronic device usage was categorized into four duration-based groups. Linear mixed-effects models were applied to examine associations between bedtime device usage patterns and global PSQI scores, as well as individual sleep components. Models were adjusted for sociodemographic, behavioral, and environmental confounders (including Normalized Difference Vegetation Index [NDVI] and artificial light at night [ALAN]). Sex-stratified analyses were conducted to identify differential susceptibility patterns. Compared to non-users (Q1), students using devices for more than 60 min before bedtime (Q4) exhibited significantly higher global PSQI scores (β = 0.87, 95% CI: 0.50–1.23) and substantially increased odds of poor sleep quality (OR = 1.85, 95% CI: 1.06–3.23). Component-specific analyses revealed heightened risks across multiple sleep components, including subjective sleep quality (OR = 1.82), sleep duration (OR = 1.87), sleep disturbances (OR = 1.85), and daytime dysfunction (OR = 1.64), mainly characterized by fatigue and excessive daytime sleepiness. Sex-stratified analyses demonstrated stronger associations among male undergraduate students, with greater deterioration in global PSQI scores (β = 1.24, 95% CI: 0.64–1.84). Bedtime electronic device usage represents a significant risk factor for impaired sleep quality among Chinese undergraduate students. These findings emphasize the urgent need for targeted sleep hygiene interventions, particularly among male undergraduate students, to reduce pre-sleep screen exposure and optimize sleep health outcomes.