Partial Blue Light Blocking Glasses at Night Advanced Sleep Phase and Reduced Daytime Irritability but Did Not Alter Salivary Melatonin Secretion in Japanese Schoolchildren

In modern society, delayed sleep patterns among schoolchildren present challenges to academic attendance and performance. The impact of nighttime light exposure, especially blue wavelength light, on sleep delay has long been acknowledged. We investigated the effects of using partial blue light blocking glasses (JINS Screen Lens Heavy [40% cut]) on salivary melatonin levels, sleep patterns, circadian phase, and daytime behavior in 39 male schoolchildren aged 10–12. Participants alternated between blue light blocking and standard clear lens glasses for three hours before bedtime, over two weeks in a crossover design, with a one-week washout interval. While blue light blocking glasses did not influence melatonin levels, they significantly advanced the sleep phase (bedtime: 22.03 ± 0.08h vs. 22.10 ± 0.1h, p < 0.05, sleep onset: 22.26 ± 0.08h vs. 22.36 ± 0.10h, p < 0.05). The effects were more pronounced in the second week and accompanied by improved irritability and reduced disruptive behavior. Blue light blocking glasses can advance sleep phase and improve behavior in schoolchildren, warranting further mechanistic investigation.