Light is as essential to our health and well-being as vitamins and exercise. Until the advent of artificial lights, the sun was the major source of lighting, and people spent their evenings in (relative) darkness. Now, in much of the world, evenings are illuminated, and people spend many hours indoors. This can have negative effects on our sleep cycles, which in turn can affect our overall health.
Blue light and the circadian cycle
Studies have shown that frequent exposure to light perceived as blue or blue-violet, with wavelengths around 450 nm, can interfere with the body’s photosensitive retinal ganglion cells that regulate sleep patterns. These cells absorb light and transmit messages to the part of the brain that governs the internal clock. The receptors in the cells send a wake-up signal to the brain in the presence of blue light, which is found in sunlight and in artificial light. This results in a variety of physical responses, including melatonin suppression.
Melatonin is the hormone that contributes to sleepiness and is thought to have many health-promoting functions. Melatonin suppression is helpful where heightened alertness is the desired effect, but it can cause problems when it affects restorative sleep. In health care settings, where patients need to rest and heal, monitoring circadian rhythms is vital.
Aren’t LEDs part of the problem?
Blue-pump LEDs have raised concerns about their potential negative effect on the circadian cycle, particularly in health care settings. But tunable lighting makes it possible to adjust the wavelength of the light emitted, making even standard LEDs capable of dropping to levels that more closely resemble incandescent light or candlelight. In color-tuned light fixtures, LED chips with different color temperatures are combined within a single fixture, making it possible to closely match natural light. (You can learn more about tunable LED lights here: How tunable white light helps patients heal.)
Vertical illuminance and LED lighting
Because the eyes absorb light levels, which can affect circadian rhythms, it is important to consider the vertical illuminance at eye level when designing LED lighting systems for health care settings. The vertical illuminance measurement indicates the amount of light exposure needed to achieve optimal health and psychological well-being and should be balanced with horizontal illuminance, or the light targeted on the work plane.
Traditional lighting design practices focused on the amount of light illuminating the work plane, rather than the light illuminating the walls, which is most often received through the eye. To stimulate the circadian system to encourage healing, lighting must provide carefully calibrated doses of light intensity and color to the corneas of the space’s occupants, which can be achieved through balanced vertical and horizontal illuminance.
LEDs are healthy
Thoughtfully designed lighting systems, including color-tuning LEDs, can mirror the variations in intensity and color that are intrinsic to the sun’s daily cycle and deliver these different types of light at the right time of day. This helps create interior spaces that support the body’s internal clock, resulting in a healthier and less disruptive alternative to the traditional built environment.