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. 2023 Nov 21;8(48):45547-45556.
doi: 10.1021/acsomega.3c05620. eCollection 2023 Dec 5.

Development and Verification of a 480 nm Blue Light Enhanced/Reduced Human-Centric LED for Light-Induced Melatonin Concentration Control

Yun Jae Eo  1 , Sung-Woo Choi  2 , Chohui Kim  2 , Seulgee Lee  2 , Chulsoo Yoon  2 , Dae Hwan Kim  3   4 , Changwook Kim  3   4 , Young Rag Do  1   4
Affiliations

Development and Verification of a 480 nm Blue Light Enhanced/Reduced Human-Centric LED for Light-Induced Melatonin Concentration Control

Yun Jae Eo et al. ACS Omega. .

Abstract

With the inherent sleep and wake cycle regulated by natural sunlight, the human body has evolved over millennia to be active during the day and to rest at night. However, maintaining an optimal 24 h cycle has become increasingly problematic in modern society as more people spend the majority of the day indoors. Many research groups have reported that inadequate artificial lighting interferes with melatonin production and disrupts the circadian rhythm. This study considered biological functions for light-emitting diodes (LEDs) of next-generation illumination, and LED packages and spectra suitable for both daytime and nighttime applications were designed. The prepared daytime human-centric (HC)-LEDs had a melanopic/photopic (M/P) ratio that was up to 26% higher than that of conventional (c)-LEDs, whereas the nighttime HC-LEDs exhibited up to a 26% lower M/P ratio compared to the c-LEDs. Nevertheless, because the HC-LED is designed to have almost the same color coordinates as the c-LED having the same correlated-color temperature (CCT), there is no change in the perceived color. To substantiate the biological effect, melatonin level data were obtained from 22 voluntary participants in c- and HC-LED lighting environments. In the HC-LED lighting environment, melatonin was suppressed by 21.9% after waking, and nocturnal melatonin secretion was increased by up to 12.2%. As human-centric lighting, our HC-LEDs are expected to become an essential element for modern life, where people spend most of their time indoors.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Fifty hour experimental schedules. Participants were admitted to the clinical laboratory at 10:00 on the first day and left at 12:00 on the third day. The lighting conditions were divided into conventional lighting and human-centric lighting (HCL). (a) Daytime conventional lighting and (b) daytime HCL with correlated-color temperature (CCT) of 5000 K. (c) Nighttime conventional lighting and (d) nighttime HCL with CCT of 2200 K. (e) Light off and sleep. All participants took part in the experiment with an interval of 1 week for both types of lighting. The black solid circles and triangles represent salivary sampling time and the questionnaire responses for assessing subjective drowsiness.
Figure 2
Figure 2
Schematic of a room where the 50 h protocol was performed and locations of the illuminance measurement. (a) Measured toward the lighting at 85 cm from the floor in the center of the room. (b) Measured toward the center of the monitor at 120 cm from the floor and 70 cm from the monitor. (c) Measured toward a facade wall at 170 cm from the floor. (d) Measured toward a regular book positioned 40 cm below 45° at 120 cm from the floor. The dimension of the room was L 6640 mm × W 2880 mm × H 2480 mm.
Figure 3
Figure 3
Comparison of relative spectral irradiance of c- and HC-LEDs at (a) daytime with a CCT of 5000 K and (b) nighttime with a CCT of 2200 K. c-LED, conventional LED; HC-LED, human-centric LED.
Figure 4
Figure 4
Microscopic images of (a) no current and (b) low current (15 mA) applied to 3.0 × 3.0 mm2 sized human-centric (HC)-LED package with two blue chips. The peak wavelengths of the light emitted from the left and right chips were approximately 480 and 450 nm, respectively.
Figure 5
Figure 5
Optical properties of daytime HC-LED with a CCT of 3000 to 6500 K. (a) Relative electroluminescence (EL) spectra as a function of the correlated-color temperature (CCT). (b) CIE color coordinates according to CCT. The gray solid line in panel b represents the Planckian locus.
Figure 6
Figure 6
Optical properties of nighttime HC-LED with a CCT of 3000 to 6500 K. (a) Relative EL spectra as a function of CCT. (b) CIE color coordinates according to CCT. The gray solid line in panel b represents the Planckian locus.
Figure 7
Figure 7
Stanford Sleep Scale (SSS) under c- and HC-LED lighting environments. All data represent mean ± standard error of the mean (SEM). *p < 0.05, **p < 0.01, and ns = not significant.
Figure 8
Figure 8
Melatonin level profiles obtained from salivary samples under c- and HC-LED. All data represent the mean ± standard error of the mean (SEM). *p < 0.05.
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