Circadian Lighting in the Built Environment

Advanced lighting and control systems can create light that changes in color and intensity throughout the day, mimicking the shifting pattern of natural sunlight to promote health and well-being
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Sponsored by Ketra
By Peter J. Arsenault, FAIA, NCARB, LEED AP
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How Circadian Rhythms Impact Sleep Patterns

In addition to the overall research described above, there are numerous other studies that look at some specific aspects of the connection between circadian rhythms and people. Some of these studies are borne out of the fact that most people in our contemporary society spend more time indoors than outside. In fact, studies show that the average American spends 90 percent of his or her time indoors, without access to adequate natural light.1 Nonetheless, it is common for people to inherently recognize the connection between natural sunlight and the healthy functioning of our bodies. Many people wish they could be outdoors more, incorporating walks into their days and getting away from their computer screens—a basic desire to reduce an indoor lifestyle and spend more time exposed to natural sunlight. It seems that we have an inherent sense of what scientific and health research are delving into to discern. These include the following types of studies and findings.

Getting a Good Night’s Sleep

People who spend the majority of their day surrounded by static indoor lighting systems rather than natural light that shifts during the day have been the focus of a number of studies. We have already noted that it has been determined that light—and especially natural shifts in daylight—is the number-one component in setting our body clocks. These clocks, or circadian rhythms, tell our bodies when to wake and sleep and are important to good health.

A study published in the June 2017 edition of Sleep Health reported on research conducted in five buildings managed by the U.S. General Services Administration.1 This study recruited 109 participants, of whom 81 participated in both winter and summer. Using a device calibrated to measure light that is effective for the circadian system (circadian-effective light), researchers collected personal light exposures in office workers and related them to their sleep and mood. It was determined that office workers who received higher levels of circadian-effective light were associated with reduced sleep onset latency (especially in winter), increased phasor magnitudes (a measure of circadian entrainment), and increased sleep quality compared to office workers who received lower levels of circadian-effective light. High levels of circadian-effective light during the entire day were also associated with increased mood (from 5–10 percent on CES-D scale), reduced depression, and increased sleep quality (10–15 percent fewer disturbances during their sleep). This study is the first to measure personal light exposures in office workers using a calibrated device that measures circadian-effective light and relates those light measures to mood, stress, and sleep. The study’s results underscore the importance of daytime light exposures for sleep health.

High levels of circadian-effective light during the entire day are also associated with increased mood (from 5–10 percent on CES-D scale), reduced depression, and increased sleep quality (10–15 percent fewer disturbances during their sleep).

Windows and Sleep Health

When it comes to the impact of windows and daylight exposure on the overall health and sleep quality of office workers, a 2014 study provides some insights.5 This research examined the impact of daylight exposure on the health of office workers from the perspective of subjective well-being and sleep quality as well as measures of light exposure, activity, and sleep-wake patterns. Measurement was performed using actigraphy, which is a non-invasive method of monitoring human rest/activity cycles. A small, wrist-watch-like actigraph unit, also called an actimetry sensor, was worn for a week to measure gross motor activity. Participants included 27 workers working in windowless environments and 22 comparable workers in workplaces with significantly more daylight. Well-being of the office workers was measured by a standard metric while sleep quality was measured by Pittsburgh Sleep Quality Index (PSQI). In addition, a subset of participants—10 workers in windowless environments and 11 workers in workplaces with windows—had actigraphy recordings to measure light exposure, activity, and sleep-wake patterns.

The study found that workers in windowless environments reported poorer scores than their counterparts on two dimensions—role limitation due to physical problems and vitality—as well as poorer overall sleep quality from the global PSQI score and the sleep disturbances component of the PSQI. Compared to the group without windows, workers with windows at the workplace had more light exposure during the workweek, a trend toward more physical activity, and longer sleep duration as measured by actigraphy. Results suggest that architectural design of office environments should place more emphasis on sufficient daylight exposure of the workers in order to promote office workers’ health and well-being. This work is reinforced by other studies that show sleep patterns in people with proper circadian rhythms showed an increase in sleep duration an average of 46 minutes compared to people with disrupted rhythms.1 Similarly, the quality of circadian reinforced sleep was measured to increase by 10-15 percent.2

Creative Technology Company Headquarters.

Photo courtesy of Ketra/Magda Biernat

Project: Creative Technology Company Headquarters
Location: New York City
Architect: A+I
Lighting Design: Lighting Workshop

In 2016, this tech office’s global headquarters was given Interior Design’s Best of Year Award in the extra-large creative/tech office category. The office environment includes an advanced lighting and controls system that flawlessly shifts throughout the day, providing natural light that is energizing and crucial for promoting employees’ productivity and overall wellness.

Light Before Bedtime

A more detailed aspect of these observations is the effect of exposure to room light before bedtime, which can suppress melatonin onset and shorten melatonin duration in humans. A 2011 study hypothesized that when people have bright light on in their rooms in the evening, it makes it harder for them to obtain healthy rest because they are not producing enough melatonin.7 In the study, they tested the quality of sleep of those who were exposed to room light (200 lux) versus dim light (3 lux). Participants were healthy in the 18- to 30-year-old range and were housed in the same facility for five days. One group was exposed to full-room light, and one group received dim light before bed. Compared with dim light, exposure to brighter room light before bedtime resulted in suppressed melatonin, resulting in a later melatonin onset in 99 percent of individuals and shortening melatonin duration by 90 minutes. This means that participants exposed to brighter room light got less sleep overall. It was found that room light exerts a profound suppressive effect on melatonin levels and shortens the body’s internal representation of night duration. Exposure to electric light in the late evening disrupts melatonin signaling and disrupts sleep, thermoregulation, blood pressure, and glucose homeostasis.

Blue light in particular has been shown to negatively impact melatonin production so exposure to it in the evening hours can also trigger the melatonin delay. That is why leading manufacturers of smartphones and tablets now have a night-shift mode on their devices in an attempt to reduce the negative impact of blue light exposure when used in the evening or at night.

Circadian Reinforced Sleep Benefits

Looking at the positive side, some studies have focused on the benefits of providing bright light in the daytime and dimmer light in the evening, revealing some specific positive effects. These studies showed that productivity in the workplace increased by 5-25 percent while people’s moods improved by a noticeable 5–10 percent on the CES-D scale.2,4 With many people seeking sleeping-aid medications to make it through the next day, it would appear they could find better relief by focusing on the conditions that help with circadian rhythms.

Productivity in the workplace increased by 5–25 percent while people’s moods improved by a noticeable 5–10 percent.2,4


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