Designing lighting for biology

Michael J. Berens

Thursday, July 05, 2018

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Decisions about how best to light an interior space tend to be based on the types of activities for which the space is being designed. While that may aid occupants as they go about their tasks, depending on the space, that lighting may be inappropriate to maintain the body’s internal clock.

That, in turn, can lead to a number of health problems. Some recent studies suggest that it is possible to better balance lighting to benefit occupants’ tasks and biological needs.

Designers and lighting engineers have long been aware of the ongoing research on the workings of the body’s internal clock.

That clock is regulated by the amount of time one is exposed to darkness and daylight within a 24-hour period. This is referred to as the body’s circadian rhythm.

Each of us has our own innate circadian rhythm, although it can be modified somewhat by environmental conditions, which is why some people function better early in the day while others function better in the evening.

As anyone who has experienced jet lag knows, if you disrupt the body’s accustomed circadian rhythm, it can wreak havoc on your sleep patterns, eating habits, ability to concentrate, energy levels, and overall sense of well-being. Moreover, research shows that prolonged disruption of one’s innate circadian rhythm can result in reduced productivity, anxiety and depression, as well as lead to severe health problems, including obesity, cardiovascular disease and cancer.

In a presentation entitled, “The Truth About Circadian Light” delivered at this year’s Lightfair, Robert Soler, the vice president of human biological technologies and research at BIOS Lighting, pointed out that present lighting standards and design practice are geared toward visual performance and comfort, not biology.

In office settings, for example, lighting conditions are set to minimize glare, increase screen visibility, and minimize energy use. These standards, however, are inappropriate to regulate our internal clock. The lighting is too dim for daylight, and too bright for night.

Consequently, says Soler, our bodies are confused. We suffer from what Soler calls “social jet lag,” the discontinuity between our innate circadian rhythm and the one we are forced to follow because of our exposure to artificial light due to work and social commitments.

One study indicates that as much as 87 percent of day workers have some form of social jet lag, and may develop health issues as a result. Adjusting lighting to accommodate for biology can lead to unwanted performance or comfort side effects, such as too much glare, too dim or uncomfortable light, or higher energy costs.

Through his and others’ research, Soler has found that selecting the proper light spectrum and distributing the light sources to provide horizontal as well as vertical illumination can better balance the illumination to meet the needs of performance, comfort and biology.

Soler also notes that circadian time is a function of both daytime and nighttime light. Hence, lighting needs to alternate between “sky” in the daytime (vertical downward lighting) and “fire” at nighttime (horizontal diffused light with no downward light).

Another way to illuminate spaces for biology is through daylighting. This may not be suitable for some work environments, but it can be especially beneficial in healthcare settings. Some recent studies have sought to determine how much daylighting is needed and how best to bring the daylight into the space.

Kyle Konis at the University of Southern California examined the effects on residents of exposure to daylight through a window in dementia care settings. Using a means he developed to measure the biological impact of the light, he found that exposure to daylight produced significant benefits by stimulating circadian function and efficacy. Important factors, he notes, are the siting of the window to the sunlight and the resident’s proximity to the window.

A team of researchers from the University of Seville in Spain and Rensselaer Polytechnic Institute in New York conducted an experiment using two hospital rooms, one located in Seville and the other in London, to gauge how factors such as window size, surface reflectances, furniture placement, and local climate affected circadian stimulus levels provided through daylighting.

They found that climate (the amount and intensity of available sunlight), the position of the patient (sitting or lying down), and the distance of the patient from the window had the greatest impact on stimulus levels.

Because it relates so directly to performance and health, research on the impact of interior lighting on circadian rhythms has focused mainly on healthcare (including senior care) and workplace environments, with some studies on education environments as well. The findings from the studies cited above indicate that lighting for biology could also provide benefits in hospitality and residential environments as well.

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