There has been a lot chatter recently about “circadian lighting” accompanied by a huge marketing push by manufactures to promote their latest and greatest tech. Applications aren’t limited to the built environment, with apps on our handheld devices and computer monitors that shift hue to limit the impact to our circadian system as well personal devices that measure and track our light exposure. “Happy lights” have been used as treatment to counteract the impacts of Seasonal Affective Disorder and its lesser cousin Winter Blues.
There is a stark disconnect between the environments we evolved and the environments we live in today. Humans alter our environment at a pace that our physiology cannot match. If we consider the transition to dense urban environments over the past couple hundred years and how this fits within the geologic time frame of millions of years, we are within merely a sliver of time within our evolutionary history. It takes more than a sliver of time for our physiology to adapt to new environments and then spread those adaptions across the gene pool.
Our ancestors rose with sun and daily activity ceased as the sun set; firelight allowed us to be active into the night. They were routinely exposed to the brightness of the day and the daily and seasonal variability of the equatorial regions of our heritage. In modern society, we rise prior to the sun, spend our commute in carsor underground trains, enter a dimly lit building where we stay for eight or more hours, and then commute home in relative darkness where we stay up late exposed to light generated by our various technological devices.
This pattern equates to Americans spending as much as 93 percent of our time indoors in environments that are not supportive of our body’s needs. There are both chronic and acute implications to the absent relationship with the sun and its life supporting light. Light is the primary cue that synchronizes our body clock to local time and being out of synch has been shown to increase the occurrence of breast cancer, type 2 diabetes, depression, cardiovascular diseaseand stress. Acutely, inappropriate light exposure can result in poor sleep, ill moods, and reduction of overall productivity.
A basic understanding of the mechanism of the circadian system can help cut through the marketing noise to find the best solution for your specific context. We have two different systems that respond to light: our visual system and the non-visual or circadian system. The visual system we learned about in high school, the rods and the cones. The non-visual system and its receptors were discovered in the latter part of the 20th century. Each system’s inputs are transmitted to different parts of the brain and result in different physiological responses. The non-visual system regulates the body’s master clock and every other time keeper across organs and individual cells.
There is a stark disconnect between the environments we evolved and the environments we live in today
The color, intensity, timing, and duration of light exposure impacts the non-visual system and thus our body clock. The peak sensitivity of the visual system is green wavelengths while the non-visual system peaks in cool or blue. The non-visual system is also blind to warm or red/amber light. We need bright light to impact the circadian system with bright cool or blueish light eliciting the greatest response. We need to be exposed for an hour or more to impact our body clock.
The body clock typically runs longer than 24 hours with light exposure acting as the regulator. If we don’t receive the proper environmental cues, then our clock can run-free and wecan become completely out of synch with the local day-night-cycle.
The start of the circadian day begins and ends at minimum core body temperature, or around 3 or 4 am for the typical 9-5 worker. Light exposure in the morning hours advances our body clock and allows us to fall asleep sooner while late afternoon and evening light retard our clock, and suppress melatonin pushing us to stay awake longer. The alarm clock and the start of our work day unfortunately is not coordinated with our delayed sleep onset resulting in a groggy and grumpy morning. If these patterns persist, the impacts compound and chronic health maladies develop.
As we spend so much of our day at work, as much as 90,000 hours over a life time, occupational settings of the 9-5 worker are very effective locations to provide a life supporting hack: scheduled variable lighting that both stimulates and is benign to our circadian system that assists in maintaining circadian entrainmentor synchronicity. The most effective way to provide this resource is through tunable lighting, or lighting that changes spectral composition. There are many flavors of this tech on the market, which houses arrays of colored LED chips, ranging from two to seven different colored diodes. The more the diodes the greater the color options and improved color consistency across the tunable range. Often, the color rich fixtures can be dual purposed for branding, greeting an expected client with their company colors, or supporting unique events such as washing the lobby with the team colors prior to a team building trip tolocal ball field.
Tunable fixtures are not absolute necessary to provide circadian supportive lighting. One could dim and increase brightness of conventional fixtures throughout the day to provide the required resource. As the color does not vary, spaces could become overly bright during the circadian impactful times, and too dim when seeking to minimize the resource. Tunable fixtures allow one to vary the circadian impact through modulation of spectra and intensity while maintaining light levels needed for visual tasks.
The control systems can be complex and rely on detailed programming and scheduling that creates a gentle, and imperceptible “circadian show” that tracks throughout the day; warmer and dim in the very early morning that ramps up to a bright-blue peak during midmorning and early afternoon, with a slow transition to a dimmer and warm conclusion to the work day. If the transitions are slow, we don’t perceive the change of color and thanks to our complex physiology, we maintain routine perception of color and space. Chromatic adaptation is the human visual system's ability to adjust to changes in illumination and color to preserve the appearance of object colors.
Commissioning the lighting system is critical to success and requires a special tool, a photoradiometer or photspectrometer that quantifies the illumination level and the spectral composition of light at the occupant’s eye. This is another departure from typical lighting design, in which measurement might not be taken at all and if so, illumination levels (absent of a spectral composition) will be measured at the work surface rather than at the occupant’s eye.
While this technology is relatively new, and practitioners are slowly adding the appropriate tools to their belt, there are many who can assist in application. Seek those with previous experience who have partnered with researchers on past projects. Be wary of those who insist that they can provide a solution, yet lack experience. The complexity of the solution demands a rigorous and technically savvy practitioner who has the experience, resources, and the passion to create nurturing and supportive environments.