The effect of reducing blue light from smartphone screen on subjective quality of sleep among students

The exposure of humans to artificial light at night (ALAN) with predominant blue part of the visible spectrum is strongly influencing circadian rhythm and sleep through melanopsin-containing retinal ganglion cells (RGC). We hypothesized that reducing the amount of emitted blue light from screens of mobile phones during the night will increase sleep quality in our student population. The aim of the work was to investigate the effect of reducing blue light from smartphone screen during the night on subjective quality of sleep among students of medicine. The target population was students of medicine aged 20 to 22 years old of both sexes. The primary outcome of the study was subjective sleep quality, assessed by the Serbian version of the Pittsburgh Sleep Quality Index (PSQI). The mean total PSQI score before intervention was 6.83 ± 2.73 (bad), while after the intervention the same score was statistically significant reduced to 3.93 ± 1.68 (good) with large effect size. The study has shown that a reduction of blue light emission from LED backlight screens of mobile phones during the night leads to improved subjective quality of sleep in students, as well as improvement in daytime functioning and going to sleep.

人类暴露于以可见光谱蓝色成分为主的夜间人工光（artificial light at night, ALAN）时，其昼夜节律与睡眠会通过表达黑视蛋白的视网膜神经节细胞（melanopsin-containing retinal ganglion cells, RGC）受到显著影响。本研究提出假设：夜间减少手机屏幕发射的蓝光量，可提升受试学生群体的睡眠质量。本研究旨在探究夜间降低智能手机屏幕蓝光发射量，对医学生主观睡眠质量的影响。研究目标人群为年龄20至22岁的男女医学生。本研究的主要结局指标为采用塞尔维亚语版匹兹堡睡眠质量指数（Pittsburgh Sleep Quality Index, PSQI）评估的主观睡眠质量。干预前，受试者的匹兹堡睡眠质量指数总均分为6.83±2.73（提示睡眠质量较差）；干预后，该得分经统计学分析显著降低至3.93±1.68（提示睡眠质量良好），且效应量较大。本研究表明，夜间降低手机LED背光屏幕的蓝光发射量，可改善医学生的主观睡眠质量，同时提升其日间功能与入睡状况。