Using Blue Light for Sleep Regulation and Melatonin Control

Sleep is a critically important biological function. This downtime gives the brain space to learn and lay down new memories, but it also affects almost every other type of body tissue and system—from the heart and lungs to metabolism, immune function, mood, and disease resistance.¹ Nearly all animals sleep, and most function on a 24-hour biological clock—although it might be governed by other external forces that make sleep in other species appear unlike our own (looking at you, dolphins, who sleep with just half your brain at a time). Even simpler creatures such as insects and nematode worms sleep in some form.

Although our human bodies have evolved to be active during the day and to rest at night, this 24-hour cycle doesn’t always fit with modern life. It is estimated that as many as 70 million Americans have a sleep disorder, which hinders daily functioning and has negative effects on health and lifespan.² In particular, blue light from devices has been found to be an ever-growing culprit responsible for bad sleep. We know that staring into our phones right before bed is terrible for sleep quality and disruptive to melatonin production, yet our compulsory scrolling habits have wormed their way into many of our pre-bedtime routines.

But it’s not just our bedtime phone habits. The proliferation of energy-efficient light-emitting diode (LED) lighting has resulted in continuous exposure to blue light in our homes, which has been linked to vision deterioration, circadian disruption, and mood disorders. Many groups have also reported that inadequate artificial lighting interferes with melatonin production and disrupts the circadian rhythm.

Not all blue light is created equal: the wavelengths that suppress melatonin production and disturb sleep are in the range of 460-500 nm, but blue light from 380-450 nm does not have the same effect. With this in mind, a team of researchers in Korea began exploring next-generation LEDs with packages and spectra designed specifically for both daytime and nighttime applications.³ The package design consists of two blue chips: one intended for daytime use with a wavelength around 480 nm, and one for evening use with a wavelength near 450 nm.

To investigate the biological effect, the team looked at melatonin data from 22 volunteers alongside a validated sleepiness scale. One week prior to the start of the study, participants were instructed to maintain their normal sleeping pattern before being exposed to the different lighting set-ups in a temperature- and humidity-controlled clinical laboratory. The results, published in ACS Omega, showed that melatonin was suppressed by 22% after waking with human-centric LEDs, and nocturnal melatonin increased by up to 12%. The authors are hopeful that their findings may one day have widespread applications in commercial LED lamps and electronic displays, helping to increase daytime productivity while improving sleep quality and relaxation at night.

During the day, it’s fine to be exposed to bright artificial lighting with radiation energy of around 480 nm, which is equivalent to actual daylight. Blue light can be minimized in human-centric lighting using a violet LED chip down-converted by red, green, and blue-emitting phosphors. However, few phosphors efficiently convert violet light to blue light. A 2021 paper in ACS Applied Materials & Interfaces reported on a new phosphor to meet this demand.⁴ A prototype device using a 405 nm LED produced a warm white light with a higher color rendering index than a commercially purchased LED light bulb while significantly reducing the blue component.

Taken together, these findings suggest more human-centric lighting set-ups are technically possible and could soon become an essential element for modern life.

References

1. Brain Basics: Understanding Sleep. National Institute of Neurological Disorders and Stroke, National Institutes of Health 2024. https://www.ninds.nih.gov/.
2. Institute of Medicine (US) Committee on Sleep Medicine and Research. Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem. Colten HR, Altevogt BM, editors. Washington (DC): National Academies Press (US); 2006. PMID: 20669438.
3. Eo, Y. J. et al. Development and Verification of a 480 nm Blue Light Enhanced/Reduced Human-Centric LED for Light-Induced Melatonin Concentration Control. ACS Omega 2023, 8, 48, 45547–45556.
4. Hariyani, S. and Brgoch, J. Advancing Human-Centric LED Lighting Using Na₂MgPO₄F:Eu²⁺. ACS Appl. Mater. Interfaces 2021, 13, 14, 16669–16676.