Why Circadian-Effective Electric Lighting Matters
“Counting sheep” is a well-known mental exercise that people use when trying to fall asleep. It is thought to have been popularized by Miguel de Cervantes in Don Quixote, who is said to have been inspired by a twelfth-century Spanish tale. Whatever its origin, it is curious to think that falling asleep has been a problem for so long, even long before the invention of electric light or social networks on smartphones. In the early 2000s, the University of Oxford developed a study to prove the effectiveness of this sheep-related method. The conclusion: this tactic does not work.
Something that is scientifically proven, however, is the relationship between the body’s production of melatonin and the feeling of sleepiness at the end of the day, which can in turn lead to a restorative night of sleep. This is directly related to the circadian rhythm, our daily biological clock. This inner “clock” synchronizes our body’s functioning and is highly influenced by the wavelengths and intensities of natural and electric light we are exposed to during the day. As we continue to spend more and more time indoors, typically with inadequate visual stimuli from electric lighting during the day, and too much stimulation from electronic devices and overhead lighting after dark – it is essential to focus on the study of lighting in architecture and how it affects people and their well-being.
For thousands of years humans only knew daylight, fire and the darkness of night, but now currently spend about 90% of our time in interior environments and are not getting the proper balance of bright days and dark nights. Although most people today live and work in civilized communities, with the convenience of human-made illumination anytime, 24 hours per day, our bodies have not changed that much compared to our ancestors. The science is very clear on the relationship between falling asleep and the light we are exposed to during the day. We (and all animals) are biologically linked to light – it is the primary stimulus for maintaining the circadian rhythm of day-active people, which depending on the individual is approximately 24 hours – and its powerful energy affects and maintains our natural biorhythms, that literally influence our ability to live, prosper and survive.
The circadian clock generates and regulates hormones and body functions throughout the day and night. If it is not synchronized with the solar day, it can have short- and long-term negative impacts on our bodies. Some of these effects can include sleep disorders, decreased performance, bad mood and even increased risk of cardiovascular disease, obesity and depression. Three main hormones are affected by this: serotonin, which is linked to our mood; cortisol, linked to the regulation of stress and blood pressure; and melatonin, which makes us sleepy and reduces the rhythm of body functions at night in order to rest. During a normal cycle, we have a cortisol peak at around 8 AM (which gives us energy to perform our daily activities) and keeps us alert until about 8 PM, when the melatonin hormones the scene, bringing sleep and rest with it.
But how does this happen? Through our eyes. The retina contains millions of photoreceptor cells which capture, record and decode light waves and, through the optic nerve, send them to the brain, where vision is processed. There are two main cell types in the visual system: Cones for Photopic (color) vision and Rods for Scotopic (low-light, gray scale) vision. In addition, intrinsically photosensitive retinal ganglion cells (ipRGCs) are distributed throughout the retina, but do not contribute much to vision and are even present in the eyes of blind people. However, the ipRGCs contain melanopsin, a light sensitive protein which has peak sensitivity to 490nm (sky blue) daylight, and when the ipRGCs are stimulated they send (non-visual) signals to the Suprachiamatic Nucleus (SCN), which in turn regulates hormone production and entrains the circadian system. In addition, the melanopic response of the ipRGCs also controls pupil size. Holistically speaking, ocular responses by the ipRGCs, cones, and rods all contribute to entraining the circadian system.
In short, lighting that is as close to the daylight spectrum as possible (during the daytime) is considered the most appropriate for our circadian rhythm. This means that from dusk-to-dawn the lights used should be less intense and more warm-toned; while from dawn-to-noon should be more intense light levels with short-wave content. It is recommended to receive 2-3 hours of intense short-wavelength light in the morning to regulate the brain and signal the production and release of hormones for the next 24 hours. After that, it is best to not expose oneself to strong lighting, as this may confuse the suprachiasmatic nucleus into releasing hormones at incorrect times.
The main issue we face today is that, as we live most of our lives in closed environments, we are bombarded during both day and night with intense lights, whether at work or at home. To make matters worse, smartphone and computer screens emit strong blue light, which confuse the brain as to whether it is day or night, stimulating the production of melanopsin. Fortunately for us, there are a number of solutions to counter this.
Spectrum Lighting’s Circadian-Effective luminaires with integral BIOS SkyBlueTM LEDs have been developed based on the latest scientific research. With a peak spectral energy of 490nm (to which melanopsin is highly sensitive), SkyBlue Bios is the first source of circadian LED to align with our body’s biological need for light. With very high melanopic ratios, SkyBlue Bios LEDs can be specified in 3000K, 3500K and 4000K color temperatures. They offer high quality white light that helps promote healthy circadian rhythms, allowing one to work more productively during the day under stimulating lighting conditions, and potentially sleep more soundly at night, when after sunset/before bedtime, one experiences lower light levels with less SkyBlue spectral energy.
By dimming the lights, users can change the spectral quality and replace the daytime wavelengths, turning the environment into a nighttime-appropriate space. The BIOS dynamic biological light engines can be combined with the BIOS Bio-Dimming™ module, which allows both intensity and spectrum to be controlled through a single channel.
By understanding our relationship with nature and how our body works, it is possible to design a system that, in addition to lighting spaces and embellishing them, can also make our bodies work better. Another happy outcome, of course, is that we won’t need to count sheep to get to sleep.
Learn more about these and other Spectrum Lighting products in our catalog.