Circadian Rhythm

Excerpts from an article by Ed Clark and Marty Brennan, originally published in Healthcare Design Magazine March 2017 


Because of our millennia-long relationship with nature, humans are attracted to the brightness at the end of perspectives. Lighting strategies cue patients to move through the metaphorical forest toward the clearing of activity spaces, where a circadian lighting solution is focused.

Circadian lighting works to support natural sleep/wake cycles in building occupants to foster both healing and well-being. Numerous studies have illustrated that reinforcing circadian patterns to correlate with local time can result in improved sleep, improved mood, and increased pharmaceutical efficacy—all highly relevant to behavioral health patients.

Circadian lighting can be incorporated via cove lights in the corridor that mimic changing lighting conditions, similar to glimpses of sky through a tree canopy. Because patients spend the majority of their time in communal patient activity areas, those should be prioritized over patient rooms as the most appropriate location to deploy impactful lighting. Light fixtures within the clearing or activity area are tune-able white, as are the cove lights in the corridors. The color of the light fixtures is programmed to change from warm (orange-ish) white in the morning and evening to cool (blue-ish) white in the mid-morning and early afternoon, in concert with the natural color variation of the sky that occurs from the blue light of sunrise to the warm light of sunset. Light is the primary means of regulating our sleep/wake pattern, and cool light is most effective at shifting our circadian patterns, while warm light will have a negligible impact.

The timing of exposure to these wavelengths is critical to maintain a circadian entrancement or sync the body clock to the local solar cycle. Providing blue light in the mid-morning to early afternoon hours has been shown to be most effective at clock regulation, while exposure to blue light later in the day can delay the body clock, delaying the time one falls asleep as well as reducing the quality of sleep. Warm light is stripped of circadian impactful wavelengths and can provide light for general tasks without negatively impacting the sleep-wake cycle.

These color and intensity shifts are not just experiential, but are used to influence physiology to reinforce patients’ and support staff members’ circadian patterns. Research has also shown that blue light provides an alerting effect, while warm light at lower intensities can have a calming effect. Using lighting color and intensity to provide a less stimulating environment in the late afternoon and evening hours can wind people down for the day and lead to less disruptive behavior.

for a pdf. version click here: Photos for Healing Newsletter #119- July ’17