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How LEDs are helping to recalibrate circadian rhythm lighting

Our bodies use blue light to regulate our sleep and wake cycles, or circadian rhythm. Historically, the sun provided the right amount of blue light to experience benefits such as increased alertness, elevated moods and heightened reaction times, but since modern humans spend so much time inside, we must rely on artificial lighting to help regulate exposure to blue light, which can be potentially hazardous in high quantities.

We spoke with Matt Petti, product manager for connected lighting with Eaton’s Lighting Division, about the impact of exposure to blue light and artificial light from LEDs on circadian rhythm.

What effect does light have on our circadian system?

MP: There is resounding research on this topic, and the overall conclusion of most researchers is that receptors in our eyes respond to nonvisual stimulation and tell our bodies when it’s day or night. The stimulation these receptors receive influences the chemical production in our bodies that either keeps us awake or helps us fall asleep. Whether you’re dealing with sunlight or artificial light, the intensity, length of exposure and wavelength of light contribute to the reactions of those receptors. The types of chemicals your body will produce — or not produce — are based on those varying factors.

Can artificial blue light disrupt circadian rhythm?

MP: If you are outdoors in the daytime, you will experience the sunlight increasing in intensity and blue light in the middle of the day, but as it gets toward the end of the day and the sun starts going down, those levels decrease.

Now, let’s say you work until 8 or 9 p.m. and are exposed to the same high-intensity light throughout the day. In situations like this, when you’re exposed to artificial light for an extended amount of time beyond what the sun provides, you’re stretching out the natural day. Your body, in turn, reacts by reducing the melatonin — the chemical it usually produces to put you into a more relaxed, sleepy state.

In fact, the Lighting Enabled Systems and Applications (LESA) center at the Rensselaer Polytechnic Institute has doctors and scientists on staff who have been looking into this. They conducted a research experiment during which they placed an high-intensity, blueish wavelength light above the user’s field of view during a workday. What they found was that while this light was active, the people in the workplace were more alert. But they were also more alert for a longer period of time after being removed from the light, which causes the body to get fatigued. So, if you’re exposed to strong blue light for significant lengths of time into the evening, it can create a real issue with circadian rhythm.

We understand what happens with too much exposure to blue light at night, but what are the consequences of too little exposure to blue light during the day?

MP: Since blue light stimuli is naturally part of sunlight but also part of artificial light, you still need the exposure during the middle of the day when, if you were working outdoors, you would be getting it from the sun. If you’re working in an office without a lot of natural light, or if the artificial light you do have spectrum, then you’re actually not getting the exposure that would normally wake your body up.

The key is all about keeping the rhythm — high in the morning and midday, low in the evening and night, high in the morning and so on. The up-and-down pattern is what sets your body’s clock. If you’re not getting more exposure to blue light in the middle of the day, but instead are immersed in it at night, you’re not following the pattern to create that rhythm.

How are LEDs changing the landscape of circadian rhythm lighting?

MP: Artificial lighting in offices, education facilities and many other ambient indoor spaces has been primarily fluorescent lighting for a long time. While the blue spectrum is available in fluorescents, it doesn’t necessarily have the same wavelengths as LED.

Considering the way LED technology is manufactured, coupled with our awareness of the effects of blue light, we can now make products that reduce or increase the amount of blue spectrum. That was never an option with fluorescents.

The major difference in switching to LED lighting is that you have more control over which specific wavelengths are being emitted. In addition to that, tunable light systems, like Eaton’s VividTune, are able to shift the color temperature, which inherently changes how much blue content there is in the light. There are even some LED systems that are designed to minimize the hazardous blue spectrum, as it is often referred to. But, even a typical tunable light system will have the capability to reduce the amount of blue light if it’s being used properly.

Tunable LED luminaires allow you to control more than just the spectrum, though. You also have control over the intensity of the light and the duration of exposure. One thing that has been apparent in the change to LED lighting is that dimming is being used significantly more than it ever was with fluorescent lighting, because LEDs allow us to do it inexpensively and control it very well. The ability to simply dim the light fixture has a significant impact on circadian rhythm, sometimes more than just adjusting wavelengths. With the ability to tune LEDs, we’ve found a modern solution to an age-old dilemma.