Abstract
Purpose :
There is growing evidence of the negative impact of light at night (LAN) on sleep. The low levels of blue light emitted by screens and domestic lighting are sufficient to induce strong melatonin suppression on young adults. Only broadband dark-orange lenses had so far been evidenced to limit this effect but with highly compromised vision. We performed a cross-over randomized clinical study in the evening home environment on young adults to compare the effects of an innovative selective filter of circadian light to non-filtering lenses and to dark-orange lenses (dark positive control) on sleep quality, melatonin production and visual comfort.
Methods :
56 healthy young adults (27.9yrs ± 5.8SD) participated. They were evening screen users devoid of any major health problem and excluded for prescription medications or sleep disruption. Each eyewear was worn 7 consecutive evenings for 4 hours prior to the usual bedtime using screens, with 7 days of wash-out in between. Hourly saliva samples (Bühlmann) were collected and radioimmuno-assayed for melatonin concentration. Sleep staging was analyzed with a digital tri-axial accelerometer (MotionWatch). Sleep and day alertness were assessed with standard Leeds and Karolinska Sleepiness Scale. Visual comfort and lens aesthetics were rated. MANOVA with Tukey tests were used for statistical analysis.
Results :
4-hour exposure to light from screens and domestic lighting with non-filtering lenses before bedtime significantly suppressed melatonin by 47% compared to the dark condition. Our selective filter reduced the suppression to 12% (p<0.001), improved objectively measured sleep duration by 27 min (p<0.001) and advanced L5 onset by 25 min (p<0.001). Leeds scores were increased with both filters, especially sleep quality (p<0.001). The visual experience was significantly improved with the selective filter compared to the dark-orange one.
Conclusions :
We bring confirmatory proof that low levels of LAN are sufficient to decrease sleep quality and melatonin production at bedtime, likely to lead to misalignment of circadian phase. Our highly selective filter significantly counteracted these effects, while considerably improving vision and lens aesthetics compared to current dark-orange lenses. Hence this new eyewear could be more easily adopted for a regular evening use for circadian rhythm balancing despite blue content in LAN.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.