Lighting for Health
Below is my contribution to the August issue of tED Magazine on the topic of lighting and health. Reprinted with permission.
For millions of years, sunrise and sunset set the human body clock, or circadian system. This system produces and regulates bodily functions such as sleep-wake cycles, body temperature and hormonal release based on 24-hour cycles, or circadian rhythms. These functions in turn are stimulated by light falling on specialized cells in the eye that convert it into neural signals.
In the modern age, humans spend the vast majority of their time indoors exposed to electric lighting systems designed primarily for vision. People also spend large amounts of time with mobile devices. This creates risks of circadian disruption that can affect health and well-bring.
“Research now tells us that a disrupted circadian system is connected to long-term health, productivity and behavioral problems such as fatigue, cancer, obesity, diabetes, depression, mood and sleep disorders, reduced physical and mental performance, and irritability,” says Bonnie Littman, President and CEO, USAI Lighting. “In essence, light is powerful and essential, and can and should be used for the betterment of human health and well-bring.”
As scientists advance our understanding of light and health, the lighting industry is beginning to experiment with practices and products that can be used to create more circadian-friendly environments.
“There is currently enough evidence to claim benefit for individual health and happiness,” says John Hollander, Director Brand Development, Hubbell Healthcare Solutions. “Where care has to be taken is claiming healing benefits or patient outcomes.”
What we know
The Lighting Research Center has identified four main characteristics that influence light’s impact on circadian health:
• Intensity: cumulative amount of light falling on the eye’s photoreceptors throughout the day—an issue of vertical, not horizontal, light levels. This may be the chief influence.
• Spectrum: wavelength of the light. Visual acuity is most responsive to “green” (medium-wavelength) light, while circadian regulation is most responsive to “blue” (short-wavelength) light. Meanwhile, “red” light can increase daytime and nighttime alertness, making it also important.
• Timing: when light and spectrum are received by the eye’s photoreceptors. A high intensity of blue light received in the morning will aid an early bedtime but can delay sleep if received in the evening.
• Duration: quantity of time of exposure. The circadian system responds slowly to light received throughout the day.
“We know with certainty that for normal populations, exposure to blue-rich light during the day supports optimal circadian health, and exposure to blue-rich light at night disrupts our circadian rhythms with negative consequences for sleep and health,” says Scott Roos, Vice President Product Design, Juno Lighting Group, an Acuity Brands company. “The ‘typical’ lighting scenario of working in a cool, brightly illuminated office during the day and a warmer, more dimly illuminated home environment during the evening is actually spot-on in terms of supporting good circadian health for normal populations.”
The devil in the details
Current research doesn’t connect health outcomes with specific lighting design strategies. Most research is conducted in laboratory conditions, and with average responses. Additionally, nighttime light exposure is as important as daytime exposure, and individual lifestyle trumps all of it.
The lighting industry understands that light and health are connected, and that lighting, as the application of light, can impact health. Practitioners have the basic understanding and tools they need to make lighting systems more circadian-friendly. They’re just not sure to what extent and for what percentage of people. And there’s currently no best practice.
“The science of illumination is expanding with varying experts’ views on applications and outcomes,” Littman says. “Creating new metrics to explain how light impacts our biological systems will be critical in realizing the promise that light has in its impact on health and productivity.”
Hollander recognizes that current research suggests some general guidelines but otherwise the industry is still learning. “There isn’t a recognized ‘prescription’ for the optimized spectrum, intensity, timing and duration,” he says. “It is very likely we will see a ‘prescription’ or template in the future with the equipment to support it.”
Ideal early applications include environments in which occupant activity and wake/sleep patterns are predictable, such as healthcare and assisted-living facilities. Roos says research is continuing and, along with the results of early adopter applications, will reveal recommended practices. He says: “Our knowledge base and ability to provide more concrete information will continue to increase.” By the time organizations such as the Illuminating Engineering Society publish a specific recommended practice, he adds, the basics of circadian lighting will be widely understood.
“Additional tools will be used to guide us,” says Littman. “There are new lighting metrics such as circadian light, circadian stimulus, melanopic lux and others that are emerging to guide lighting product development and lighting design practice.”
“Research has shown that by providing exposure to natural light throughout the day or electric illumination where the intensity and spectrum is adjusted for the time of day, individuals experience a more typical sleep/wake pattern,” Hollander says.
He points to research specifically recommending introduction of blue-rich light starting in the morning with an intensity of 30-40 vertical footcandles. The light would then transition to a warmer spectrum and lower light levels at late afternoon and into the evening. At home, intensity would then drop to 1-2 footcandles before total darkness at bedtime.
Looking at a typical commercial building with workers occupying it on a 9-5 schedule, several elements are needed in the lighting design. Since we are concerned with vertical illumination, the lighting must deliver sufficient light on vertical surfaces such as walls. Task lighting can efficiently provide high local vertical light levels. The lighting system must be properly controlled to automatically adjust intensity and optimally spectrum during the day on a schedule. Ideally, occupants will be exposed to daylight. If they don’t have access to daylight, they should be encouraged to take a 30-minute walk outside in daylight in the morning. Finally, they should be educated about good nighttime lighting practices.
Circadian lighting and LED sources with intelligent control are ideally matched. “We are starting to characterize the circadian content of various light sources, which is different than the visual amount of light as measured in lumens or footcandles,” Roos says. “Understanding this will help us do a better job selecting the most efficient light source in terms of either eliciting a circadian response during the day or preventing it at night. As we continue the migration toward LED technology, we will have more refined ways to optimize the quality and amount of light both during the day and at night. For example, we can now spectrally tune LEDs to insert or remove blue content and can specify warm dimming as an option.”
Distributors interested in circadian lighting should get educated about the latest research and principles, and identify experts and manufacturers that can be used as a resource. Distributors may also benefit from being able to point out poor approaches, such as a space that operates during the day and night but maintains blue-rich, high-intensity light at night instead of adjusting to warmer, lower-intensity light.
“Like any new field, it will likely take a decade or more to become mainstream, but that creates a great opportunity for you to lead your organization into this emerging field,” Roos says. “An opportunity to create your network of experts that allow you to step into a non-commoditized ‘blue ocean’ field and differentiate yourself in your served markets.”
Hollander concludes: “The convergence of growing research on the connection between lighting and health and the capabilities of solid-state lighting and controls presents an exciting opportunity. We can dramatically change our approaches to lighting spaces and deliver a new level of interaction between occupants and their space.”