LAUSR

A late bedtime is one of the most common characteristics of sleep habits in modern society. This is also the case for schoolchildren, with negative consequences for their academic performance. Light exposure at night, particularly blue wavelength light, was thought to delay bedtime, and melatonin suppression via blue light was considered to be one of the mechanisms responsible for the delayed sleep phase. In the current study, we evaluated the effects of partial blue light blocking glasses (JINS Screen Lens Heavy [40%cut]) on salivary melatonin levels, sleep and circadian phase and daytime behavior (via actigraphs and questionnaires), with and without blue light blocking (JINS Standard Clean Lens) glasses in 39 male school children (ages between 10-12). The study design was a cross over design, with respective glasses worn for 3 hours before the habitual bedtime for two weeks, with a one-week washout period (with their own regular glasses) in between sessions. Saliva collections and questionnaires were performed during the first and second weeks of each session, with saliva collected -3, -2, -1, and 0 hours before the habitual bedtime. Actigraph data were collected throughout the evaluation periods. We found that while partial blue light blocking glasses had no effect on salivary melatonin levels, they did significantly advance the sleep phase compared to the non-filter session (bedtime: 22.03±0.08h vs. 22.1±0.1h, sleep onset: 22.26±0.08h vs. 22.36±0.10h, p= 0.04). The filter effects were most noticeable in the second week, where significant advances in bedtime (-0.12h, p=0.03), sleep onset (-0.14h, p=0.03), wake up time (-0.13h, p=0.02), and leaving-bed time (-0.14h, p=0.02) from the 1st week were observed, whereas no changes were seen during the control session (without filter). Along with the sleep phase advancement observed, daytime irritability and acting out towards siblings and friends were significantly reduced in the second week of the filter session. Our results suggest that partial blue light blocking glasses advanced the sleep phase and improved behavior in schoolchildren, but that the effects were not mediated by changes in melatonin secretion. Further research into the mechanisms involved is warranted. This study was supported by Jins Holdings Inc (SPO236998).