Effects of evening exposure to light from organic light-emitting diodes on melatonin and sleep

Abstract

Background and Purpose Organic light-emitting diodes (OLEDs) emit less blue light than traditional light-emitting diodes (LEDs), but the effects of OLED light exposure (LE) on mel-atonin and sleep have not been evaluated. Methods Twenty-four healthy subjects (age 26.9±5.7 years; including 18 females) with the intermediate chronotype were exposed to three different light conditions [4,000 K 150 lux OLED LE, 4,000 K 150 lux LED LE, and dim light (DL) at <10 lux] for 6.5 h from 17:30 to 24:00, in a random order and with a 1-week interval. Participants entered the unit for the experiment at 16:00, and their daylight was measured by actigraphy from 8:00 to 16:00 during each ses-sion. Saliva samples for melatonin were taken every hour from 18:00 to 24:00. Sleep was moni-tored by polysomnography, and vigilance was evaluated by psychomotor vigilance test upon awakening. Results Melatonin onset occurred at 21:11±01:24, 21:20±01:19, and 21:36±01:16 in the DL, OLED, and LED conditions, respectively. Melatonin onset was significantly delayed under LED LE compared to DL (p=0.007) but did not differ under OLED LE (p=0.245). Melatonin suppression, sleep parameters, and vigilance were similar among the three light conditions. The accumulated amount of daytime light in each session was negatively correlated with the mela-tonin onset time under the DL (rho=-0.634, p=0.002) and OLED (rho=-0.447, p=0.029) con-ditions, not under the LED condition (p=0.129). Conclusions Melatonin onset under OLED LE was not significantly delayed compared to DL. Exposure to sufficient daylight may advance melatonin onset even when a subject is exposed to OLED LE in the evening.