Designing for Health: Light, Circadian Rhythms, and the Health of Caregivers

Image courtesy Perkins+Will

As the green movement matures to embrace a more holistic definition of human and environmental health, building owners look to a framework of ‘wellness in the workplace’ to establish the business case for sustainable practices. The triple bottom line (for people, for the planet, for profit) takes on a unique significance for the healthcare sector. What are the implications for ‘wellness in the workplace’ when that workplace is a healthcare facility?

The United States is facing a nursing shortage crisis, with recent estimates projecting one million registered nurse vacancies by 2024. At the same time, healthcare is projected to add more jobs than any other sector due to an increasingly aging population and greater demand for healthcare services. Given that a single hospital might spend millions to recruit and retain staff, could hospital design play a role in attracting and maintaining high-performing and satisfied caregivers?

In this article we look at how designers might use light—both daylight and electric—to make a positive impact on caregiver health and wellness. While the impact of light on patient outcomes has been particularly well studied, there is less data on the impact of light on hospital staff. There are two ways in which light conditions can support staff wellness with respect to circadian rhythms: adequate exposure to daylight during day hours, and limited or controlled exposure to artificial light at night. We will look at four architectural strategies that bring daylight deep into traditionally artificially lit staff space, and two principles for designing artificial lighting schemes that support caregiver circadian health.

I. Maximizing Biological Light: Four Daylighting Strategies
Daylight is electromagnetic radiation in a balanced wavelength range that is visible to the human eye. It holds three primary, distinct functions for human health: enabling vision; chronobiology (i.e. the circadian functions, which dictate sleep patterns, mood, digestion, and cognitive abilities); and photochemistry in the skin (e.g. UV radiation and its impact on vitamin D production). The latter two functions can be considered the “nonvisual” functions of light; they operate via completely distinct pathways in the body than vision, and are significantly less well understood than the visual pathway.

Studies suggest that daylight and artificial light are interchangeable when it comes to enabling visual tasks. However, proper functioning of the circadian system is strongly dependent on exposure to natural sunlight. Under ideal conditions, daylight stimulus received in the morning hours will trigger the series of digestive, hormonal, and neurological responses that carry us through the rest of the day and night. Admittedly, a challenge for designers and architects is that the precise composition or quantity of daylight necessary for proper circadian alignment is unknown, and the lighting and design industries are still in the process of developing a metric to characterize and quantify circadian light.

The following projects illustrate daylighting strategies that channel daylight into traditionally artificially lit spaces, and thereby reduce the biological darkness that characterizes spaces that are more than 15 feet from the façade of the building.

Chinook Regional Hospital by Perkins+Will and Group2 Architecture, Lethbridge, Alberta, Canada.

Figs. 1 and 2 – Chinook Regional Hospital, Light Scoop

The LEED Silver renovation and addition Chinook Regional Hospital brings light into the central corridor of the hospital through the use of a light scoop—a south-facing skylight with tilted panels that provides an optimal balance of daylight in different seasons. Unlike conventional horizontal skylights, which may provide too much light in summer months and not enough in winter, light scoops can be particularly calibrated in Northern hemispheres to account for the seasonal paths of the sun to meet target light levels while minimizing solar heat gain.

Glass floors, clerestories, and a thin floor plate maximize the impact of the light scoop and drive daylight further into typically dark and uninviting corridors. The design also features a landscaped courtyard and roof terrace that promote a connection to nature and healing outdoor space that can incentivize staff to seek daylight exposure during breaks. Supporting patient recovery and staff well-being was a primary motivation in this renovation, and access to daylight and views were a goal for the design team from the start, with hopes of improving patient outcomes and staff retention.

Center for Obesity and Diabetes (“CEMDOE”) by Perkins+Will, Santo Domingo, Dominican Republic.

Fig. 3 – CEMDOE rendering, Light Wells showing on roof

The Center for Obesity and Diabetes has a social mission to lower the burden of diabetes in the Dominican Republic. The design supports a business model that focuses on education, lifestyle changes, and disease management, all of which requires a high degree of collaboration between specialists, healthcare providers, and patients.

The clinic experience was designed to foster this multi-disciplinary approach through patient-staff ‘pods’ organized around an interior courtyard paradigm. Light wells, or shafts, bring daylight from the roof of building through two floorplate to bring abundant daylight into a core area around which the staff and patient zones are situated. Unlike traditional top lighting strategies (e.g. skylights), which might be limited to one floor only, a light well penetrates multiple stories. By situating the lightwell in the public zone, staff and patients are equally able to benefit from the natural light, reducing the dependence of staff on ‘borrowed’ daylight through windows in patient zones.

American University of Beirut Medical Center by Perkins+Will, Beirut, Lebanon.

Figs. 4 and 5 – AUB, heliostat solar chimney

At the American University of Beirut Medical Center (AUB MC), a solar chimney harvests daylight from the roof of the building through to the basement, filling a central atrium with daylight. This exposure is enhanced through the use of a heliostat, a device that follows the sun’s rotation throughout the day, concentrating and reflecting the sun’s rays onto a fixed target.

Memorial Sloan Kettering (MSK) Monmouth Cancer Center by Perkins+Will, Monmouth, New Jersey, USA.

This dramatic renovation transformed a vacant 400,000 square foot, rectalinear office building into an inviting, daylight-filled cancer treatment center. Designers cut deep into the floorplate to create a courtyard that ushers in daylight while also providing views to nature and undulating interior walkways. The center’s main entrance is a glass-enclosed pedestrian bridge that follows the east to west arc of the sun, mazimizing daylight exposure throughout the day.

Through the strategic cut and courtyard strategy, sunlight penetrates even the lower levels of the building, providing lighting to the radiation oncology departments. Strategically placed skylights bring daylight to the entry of the Linear Accelerators, reducing the biological darkness that is particularly common in imaging departments.

II. Mitigating the Circadian Disruption: 2 Principles to Consider for Artificial Lighting Schemes
While access to adequate, daily natural light is critical to all staff, a growing body of evidence is pointing to the disruptive impacts of artificial light exposure at night and its role in circadian misalignment. Approximately one in four healthcare workers is engaged in shiftwork and as a result, has a circadian rhythm that remains permanently out of phase with natural light and dark cycles. In 2007, the IARC classified circadian-disrupting shiftwork as “probably carcinogenic.” Studies have found that, compared to day workers, night shift workers are at a 40% excess risk to develop cardiovascular disease, are twice as likely to develop ulcers and other GI issues, and have 26% higher risk of preterm delivery. Shift workers are also subject to decreased productivity, alertness, and vigilance, which may contribute to more errors on the job. In particular, short wavelength (i.e. blue) light exposure at night suppresses melatonin, which in turn is linked to increased risk for a number of diseases, including breast cancer.

Below are considerations for designing with circadian health in mind. While this is an area that is less well understood than daylight—and current small-scale studies do not easily translate to broadly applicable design guidelines—there are certain hypotheses that building planners can make based on the growing body of research to suggest that well-timed delivery of calibrated artificial light can have regulatory effects on the circadian system.

Consider Peak Sensitivities
Research suggests that the type of omnipresent, dim illumination that is present in our urban environments may be insufficient to trigger circadian responses and also may be contributing to increased light sensitivity at night. The ganglion cells that function as receptors for circadian light are particularly sensitive to wavelengths in the blue (i.e. short) range, which are at peak concentrations in morning daylight. This well-timed blue light has the biological effect of suppressing melatonin—thereby reducing feelings of sleepiness—and stimulating cortisol production, resulting in increased alertness for daytime activity. This morning, high intensity light also has the effect of regulating a series of physiological responses that commence throughout the day, such as bowel movements in the mid-morning, increased reaction times and alertness by mid-day, and high blood pressure and body temperature in the early evening.

When designing staff zones, consider the activities that take place throughout the day with respect to daylight composition at those times. For instance, if staff are more likely to be in a biologically dark (i.e. non daylit) space in the morning hours, this increases the importance of outfitting high intensity, blue light spectrum fixtures in order to support morning circadian entrainment. During evening hours, consider whether task illuminance thresholds can be met through amber and red lights, and through indirect lighting. For example, amber wayfinding lighting integrated into toekicks and wall bases can illuminate pathways and support nighttime navigation, while minimizing the amount of light that is received by the eyes.

Consider Variability
One of the greatest advantages of daylight is its dynamic quality, changing composition throughout the day, season, and location along the hemisphere. By comparison, traditional electric light is uniform in color temperature and constant throughout the day. Tunable light fixtures can be programed to subtly change color temperature and light source throughout the day. For example, in the case of the lighting schemes recommended by the Lighting Research Center at Rensselaer Polytechnic Institute for nurse’s stations, desk luminaires providing saturated blue light in the early morning could gradually shift to an amber light by the evening shift, which research shows has the potential to maintain alertness at night without suppressing melatonin.

At the new headquarters for the American Society of Interior Designers, Perkins + Will designers incorporated tunable light fixtures to mimic the daily color temperature cycle of the sun. As a biophilic design concept, in this case driven by the WELL Building Standard, the gradual change in light quality reinforces the passage of time throughout the day and also eases the light to dark adaptation of the visual system. The WELL Building Standard aims to optimize the way buildings advance human health, particularly in the workplace, and as such has embraced circadian supportive-lighting as a key feature to support human health for workers. The potential for improved health among staff is even greater when that population is shift workers in a healthcare setting.

Conclusion and Further Research
North Americans now spend over 90% of our time indoors, and our separation from natural sources of light has never been more pronounced. At the same time, it is becoming increasingly clear that when it comes to the non-visual aspects of daylight—the vast neuronal and hormonal pathways that impact sleep, mood, diet, and more—artificial light has been unable to offer a suitable substitute. With the number of health risks associated with disruptions in this circadian pathway, and with the number of growing number of healthcare workers that experience circadian disruption, it merits consideration as to whether the build environment can better support the health of our healthcare workers. The strategies discussed here are hopefully a starting point for practitioners to consider the way daylight and artificial light impact staff in nontraditional (i.e. nonvisual) ways.

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