Psychophysiological Effects of Dusk Simulated Light Environment on the Succeeding Sleep

Abstract

There are a lot of study about effects of light environment on sleep because light has non-visual physiological arousal effects. However, psychophysiological effects of dusk simulated light environment on the succeeding sleep is not yet clear. Accordingly, the purpose of this study was to investigate that the effects of dusk simulated light, in which both amount and correlated color temperature of the LED light is regulated to become gradually lower, on the psychophysiological state of the succeeding sleep. Light conditions were five; one was incandescent lamp with constant light amount (IL), and the other four were dusk simulated polychromatic neutral white and bulb color combined LEDs, of which excitation light is violet (P-) or blue (B-), with two patterns of light control (Twilight or Acute). Participants were 17 young male adults without problems of sleep, and slept for seven hours after light exposure, with one light condition per night, for about 110 minutes. As for the sleep architecture such as sleep stage ratio and sleep latency, there were no significant differences between the five light conditions. However, the relationship between the increasing rate of EEG-delta power component during first 20-minutes and the sleep stage transition time from sleep onset showed significant negative correlation except for blue excitation LEDs conditions. Therefore, it was suggested that the sleep onset process is more natural under the condition of incandescent lamp and of violet excitation LEDs than under the condition of blue excitation LEDs. In addition, the results under the dusk simulated LEDs were compared with those under the constant light amount LEDs used in our previous study, and we considered which is more suitable for light environment before nocturnal sleep. As a result, some of the scores of subjective sleep feelings at the time of waking up were significantly higher in the dusk simulated LEDs condition. Furthermore, the correlation during sleep onset tended to be similar in previous studies. From the above results, it was suggested that the dusk simulated LEDs condition is more suitable as the nocturnal light environment before sleep than the LEDs lighting under the steady condition, and in particular, the violet excitation LEDs may have a psychophysiological affinity.