ABSTRACT
We examined whether dynamic light across a scheduled 16-h waking day influences cognitive performance, visual comfort, melatonin secretion, sleepiness and sleep under strictly controlled laboratory conditions of 49-h duration.
Participants spent the first 5-h in the evening under standard lighting, followed by an 8-h nocturnal sleep episode at habitual bedtimes. Thereafter volunteers either woke up with static daylight LED (100 lux and 4000 Kelvin) or with a dynamic daylight LED that changed color (2700 – 5000 Kelvin) and intensity (0 - 100 lux) across the scheduled 16-h waking day. This was followed by an 8-h nocturnal treatment sleep episode at habitual bedtimes. Thereafter, volunteers spent another 12-h either under static or dynamic light during scheduled wakefulness.
Under dynamic light, evening melatonin levels were less suppressed 1.5hours prior to usual bedtime, and participants felt less vigilant in the evening compared to static light. Sleep latency was significantly shorter in both the baseline and treatment night compared to the static light condition while sleep structure, sleep quality, cognitive performance and visual comfort did not significantly change. Our results support the recommendation of using blue-depleted light and low illuminances in the late evening, which can be achieved by a dynamically changing daylight LED solution.
Competing Interest Statement
Competing interests: The authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: KK and YS are employees of Toshiba Materials, Japan. OS is listed as an inventor on the following patents: US8646939B2—Display system having circadian effect on humans; DE102010047207B4—Projection system and method for projecting image content; US8994292B2—Adaptive lighting system; WO2006013041A1—Projection device and filter therefor; WO2016092112A1—Method for the selective adjustment of a desired brightness and/or color of a specific spatial area, and data processing device therefor. OS is a member of the Daylight Academy. OS has had the following commercial interests in the last two years (2017-18) related to lighting: Investigator-initiated research grants from Derungs, Audi, VW, Porsche, Festo, ZDF and Toshiba; Speaker fees for invited seminars from Merck, Fraunhofer, Firalux and Selux. CC has had the following commercial interests in the last two years (2017-2018) related to lighting: honoraria, travel, accommodation and/or meals for invited keynote lectures, conference presentations or teaching from Toshiba Materials, Velux, Firalux, Lighting Europe, Electrosuisse, Novartis, Roche, Elite, Servier, and WIR Bank. CC is a member of the Daylight Academy. MF, SV, TB, MM and JW do not report any conflict of interest. Funding: The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The study was supported by VELUX Stiftung (Project number: 1062) and Toshiba Materials, Japan.
