Effects of nighttime lights by LED and fluorescent lighting on human melatonin

In this study, we used an LED (light-emitting diodes) light source to develop the the best combination of light wavelengths for nighttime lighting based on the LED advantages of narrow band and controllable spectrum.The action spectrum is based the research of Professor Brainard in the field of non-visual response model, which is used for designing circadian stimulation of LED. The CS/Lm (Circadian stimulus/Photonics lumens) values were calculated from the equations, which resulted in 8.9 × 10⁻⁴ for Fluorescent lighting (FL) of correlated color temperature (CCT) 5000 K, 5.2 × 10⁻⁴ for FL of CCT 3000 K and 4.4 × 10⁻⁴ for LED lighting of CCT 3000 K. Eight healthy males were exposed to various lighting conditions at midnight, and the physiological parameters including pupil diameter, melatonin secretion, delay of melatonin onset (DLMO), rectal temperature and subjective sleepiness were measured. Two results from the experiment were generated. Result (1) shows that LED 3000 K demonstrated the melatonin significantly increased (p < 0.05) when the light exposures of LED 3000 K, FL 3000 K and FL 5000 K reached retina with identical quantum state. Result (2) shows the melatonin onset in the 2nd night under LED 3000 K was almost the same as that under dim condition. The experimental results show that LED lighting will lead to lower interference on melatonin and DLMO than fluorescent lights, which is similar to the result of CS value. This paper provides a sound basis for designing LED spectrum concepts. By the simulation spectrum program develops, and the experiment verification. LED light source shows a high-value potential to use in our daily life.