Lighting color and human response: Why lighting is critical to healthy design

January 19, 2016 Lauren MacLeod

The color of lighting: It matters to your building (and the people in it)


As a professional lighting designer, I am fascinated with the effects of light on the human body’s daily biological cycle, or circadian rhythm. I’ve done much research over the years on this subject, which really began in hospital neonatal intensive care units (NICU), one of the first areas where scientists, doctors, and lighting designers noticed a correlation between baby recovery times and the light sources and colors to which they’re exposed. We’ve learned that the effect of light on patients is critical.

“Lighting is not neutral!!! It will have either a positive or negative effect on human health.”
— Presented at Lightfair International in New York City in May of 2015 by Dr. Joan E. Roberts, PhD, Professor of Chemistry, Fordham University Department of Natural Sciences, New York

Lately there has been a great deal of mainstream media coverage of the numerous studies that have sounded the alarm to the general population on how blue light at night from televisions, computers, cell phones, tablets, and clock radios can affect our health. Blue light can reduce or even shut down the production of melatonin (the body’s hormone that responds to light and sleep) in our bodies, which is the hormone that helps us fall to sleep and, most importantly, moves us into delta sleep. Delta sleep is the restorative sleep period when our bodies rebuild and heal. The same is true for bright white light or white light that has a spectral distribution high in blue wave length (which includes fluorescent, metal halide, and LED sources).

When exposed to natural light, our circadian rhythm follows the change of light color through the day and as the light changes from shortwave blue light in the morning hours to longwave red light in the late afternoon hours. Blue light in the morning from 6:00-10:00am sets our circadian, and the longer red wave lengths after 2pm in the afternoon triggers melatonin production.



Taking these studies to the next level—the workplace.
We’re beginning to understand that people with jobs like nurses and doctors can also be negatively affected by the wrong colors of light. With knowledge of light’s effects on melatonin, it was once commonly believed that shift workers should be exposed to “blue light” at night to stay alert and productive.

Newer studies now tell us a different story. For starters, the suppression of melatonin from blue light at night has actually been linked to a variety of increased health risks. Shift workers can deal with obesity, hypertension, heart disease, cardiovascular disease, diabetes, and even cancer, among other issues. 

In February 2015 the Lighting Research Center (LRC) released a study that shows the results of tests of red light on nighttime shift workers. The study indicated that red light – not surprisingly – did not suppress melatonin (and interrupt the circadian). But, in fact, alertness and performance actually increased under the red light. This was very surprising!

Hospital staff, for example, may not have access to daylight or outdoors, but we can design our lighting systems within the specific bandwidths to trigger the circadian rhythm. In the past it was a little more cumbersome to design lighting for circadian, but now with the advance in LEDs and controls, it’s relatively simple. With LEDs, we can select the exact wave lengths, and with controls, we can create an automated system to emulate electric light, day through night.

Studies of the effect of light on humans and animals has been in development for a while, but it seems to be progressing more quickly now. I don’t doubt it will affect how we light spaces in all spheres, including hospitals, nursing facilities, schools, offices, public buildings, and our homes! As part of the larger design community, we want to do all we can to bring daylight into the built environment. As lighting designers, we take great care in how we add electric light to those spaces. There will be much more to come in this field – we are only just beginning to learn. 

About the Author

Lauren MacLeod

Lauren MacLeod, IALD, MIES, LEED AP, is a principal and senior lighting designer in our Lighting Design team. Knowing that light can affect well-being (good and bad), Lauren stays abreast of leading scientific research and uses findings to design lighting scenarios that benefit users of spaces in cultural, hospitality, education, healthcare, residential, retail, corporate and exterior landscape environments.

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