The impact of smartphones pre-bedtime on sleep quality: A controlled crossover study with university students in China

The quality of the indoor environment is critical for sleep. As smartphone use continues to rise, these devices has become integral to daily life, particularly amongst young adults. Many students engage with short-form video applications pre-bedtime, which has been linked to poorer sleep quality and next-day cognitive performance. To explore aforementioned factors quantitatively, 18 University students were recruited as participants. They were sequentially exposed to three conditions: a 60 min baseline, a 30 min condition and a 0 min condition. Polysomnography technology was used to continuously monitor electroencephalogram, electro-ophthalmogram and other signals during sleep. Subsequently, participants were asked to complete a subjective-response questionnaire and an early-morning cognitive assessment. A comprehensive analysis was then conducted to evaluate sleep quality and quantify its impact. Baseline survey data ( N = 211) revealed that 89.6% of university students used smartphones pre-bedtime and 64.5% watched short-form videos. During the experimental phase, compared to baseline condition, progressively limiting short video exposure to 30 and 0 min increased sleep efficiency by 5.43% and 11.51%, respectively, reduced Wakefulness After Sleep Onset by 35.3 min and 46.4 min, raised positive effect scores by 2.33 and 5.44 points, and improved N-back accuracy by 3.5% and 5.5%.