The Fifth Generation of Light Has Arrived

Spectrum of day and night circadian lighting

Source: Korrus

Call it the fifth generation of light—the availability of electric lights that promote health and well-being by automatically mimicking the natural cycle of light. They switch between blue-rich daytime light and zero-blue light at night without requiring large changes in brightness or correlated color temperature (CCT).

The History of Light Exposure

The history of human exposure to light is coming full circle with the arrival of such circadian lighting.

The First Generation of Light

For the first 10,000 generations of human existence, our ancestors were bathed in blue-rich daylight and slept in the dark at night. This alternation between bright blue-rich daylight and the absence of blue at night is the key signal that keeps the 24-hour rhythmic processes of our bodies, called circadian rhythms, in harmony with the natural world.

The Second Generation of Light

Around 250,000 years ago, humans first gained control of fire. Blue-free wood fires and candlelight (from 3,000 years ago) freed humans from the tyranny of night without disrupting our circadian rhythms—although they coated all interiors with soot.

The Third Generation of Light

In 1882, in New York City, Thomas Edison introduced the incandescent light bulb, which was followed by other low-blue electric light sources. These new lights enabled us to conquer the night—but they were inefficient in their use of energy.

The Fourth Generation of Light

2014 was the start of the widespread adoption of ⁓ 450 nm Royal Blue pump LEDs, which provided a 20-fold increase in lumens of light produced per watt of electricity—but their bright blue-rich light came at an enormous cost to human health at night. Recently, 248 leading circadian scientists called for blue-pump LED lights to carry a warning label, “May be harmful when used at night,” because of the significantly increased risk of sleep disorders, obesity, diabetes, heart disease, and certain cancers, all potential consequences of disrupting normal circadian rhythms..

The Fifth Generation of Light

Circadian blue lights automatically provide an effective dose of sky-blue light throughout the day and a safe, non-disruptive level of blue light at night. They supply the blue doses required for good health while providing the high-quality white light day and night that we need to live and work by.

Why Is It So Important to Control Sky-Blue Light Wavelengths?

Out of all the rainbow colors of the natural light spectrum, a narrow band of sky-blue light, between 440-495 nm, provides the key signal to our circadian clocks that it is day or it is night. These blue wavelengths are 25 times more effective than the other color components of the white light spectrum in resetting circadian clocks because they are detected by blue-sensitive melanopsin-containing cells in the retina of our eyes.

Sky-blue light during the day synchronizes and strengthens our circadian rhythms. But after the sun sets, exposure to these same blue wavelengths disrupts our circadian clocks—because they give the false signal that it is daytime and not night.

The irony is that, to save the planet's health, the U.S. Department of Energy has been promoting blue-pump LED lighting that harms human health when used at night. In 2013, LEDs comprised only 1 percent of lighting sales, but by 2024, LEDs were in over 70 percent of all lighting sold worldwide. Low-blue light sources like incandescent and halogen bulbs are now banned, and until today, the only lights readily available have been ⁓450 nm Royal Blue pump LED.

Development of Evidence-Based Circadian Lighting

The discovery, by my team, that most of the circadian impact of light fell within a narrow band of 440-495 nm sky-blue wavelengths made possible the design of white LED light that was either blue-rich or blue-depleted. A key breakthrough was our finding that we could create an attractive warm white light for evening and night use by replacing the blue LED chip with a violet LED chip in the 415-425 nm range. The human eye responds to violet for only the first hour after nocturnal darkness, but once our eyes are fully light-adapted, violet light has minimal effects on circadian clocks for the rest of the waking day. So, by using a violet LED chip, we could balance the color spectrum in the absence of blue light and create a light with an acceptable, warm white color.

Over the past 10 years, we have demonstrated the benefits of circadian lighting in controlled studies with human volunteers in the Circadian Light Research Center we built on Boston’s Route 128 high-tech corridor. Then, over the past five years, we have studied the efficacy and safety of circadian lighting installed in 65 safety-critical workplaces, including Chevron, Dow Chemical, the U.S. Coastguard, Duke Energy, and National Grid.

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Circadian Light Research Center

In the controlled environment of the Circadian Light Research Center, we showed that there were substantial benefits to using blue-depleted circadian lights during the evening and night hours as opposed to conventional blue-enriched LED lights.

• Total overnight melatonin production was significantly increased under blue-depleted circadian night lights. With less than 2 percent blue lights at night, over six times more melatonin was produced between 8:00 p.m. and 8:00 a.m., compared to conventional blue-rich LED lights at the same illumination intensity. We can reasonably conclude that low blue lights at night protect and enhance the multiple benefits of nocturnal melatonin in suppressing cancer cells and supporting healthy metabolism and immunity.
• Glucose intolerance and insulin resistance were prevented by blue-depleted lights. With nighttime exposure to conventional blue-rich LED lights, insulin resistance was doubled, pitching the healthy subjects into a pre-diabetic state. In contrast, blue-depleted circadian night lights prevented the pre-diabetic condition, even though both lights were at the same illumination intensity.
• Increased appetite induced by blue-rich LED lights at night was reversed by the blue-depleted circadian night lights. This increased appetite generally leads to more snacking on the night shift and the excessive obesity too often seen in night- or rotating-shift workers.
• Circadian disruption was prevented by blue-depleted lights. Conventional blue-enriched LED lights during an overnight study delay-shifted the peak of melatonin production. This disruption in circadian timing was reversed by the blue-depleted LED lights at the same illumination intensity.
• Vigilance performance was improved by the blue-depleted violet-pump circadian night lights. Conventional blue-pump LED lights increased vigilance performance but not as much as the violet-pump circadian night lights. And the circadian blue-depleted night lights improved performance without causing all the other undesirable effects of blue-enriched LED light at night.

Installations in Fortune 500 Workplaces

We conducted one-year follow-up studies comparing the previous conventional fluorescent or blue-pump LED lighting with the circadian day-night lighting systems and demonstrated:

• Improved sleep duration and quality were shown both before and after night shifts in people working rotating shifts around the clock, as the circadian lights prevented disruption of the workers’ circadian rhythms.
• A 50 percent reduction in excessive sleepiness was measured on the Epworth Scale, a well-established measure of daytime sleepiness.
• A 100 percent increase in alertness at 5 a.m. was measured. This is the hardest time to stay awake on night shifts, a time when errors and accidents caused by inattention reach their peak.
• A 45 percent reduction in the average number of snacks eaten during night shifts. This can lead to weight gain, which is prevented by circadian lighting.
• A 20 percent reduction in gastrointestinal disorders in people working shifts around the clock, because of reduced circadian disruption when low blue light is used at night.
• A 67 percent reduction in operator errors in people working in safety-sensitive control room operations controlling multibillion dollar businesses.
• A 43 percent reduction in the use of over-the-counter (OTC) pain medications:

The lighting technology that we invented at the Circadian Light Research Center is now on its way to becoming widely available. Korrus is introducing architectural lighting fixtures with circadian blue lights at the LEDucation show in New York on Tuesday, March 19, 2024, then automated circadian light bulbs. The technology will also be incorporated into the computer screens that we sit in front of all day.