Beyond the Ceiling: Healthy Lighting for Hospitals
Lighting systems have historically been designed for visual performance and comfort, but science tells us light plays a major role in synchronizing the human circadian system. The growing understanding of the relationship between light and circadian health is giving rise to a new lighting trend: circadian lighting.
Hospitals present a particularly interesting application. This is an environment specifically designed to promote health where managers are concerned both with the well-being of workers and their patients.
The human body regulates biological functions based on 24-hour cycles known as circadian rhythms—one being timing the release of the hormone melatonin, which tells the body when it is time to sleep.
Disruption of the body’s internal clock also affects the timing of these bodily functions and, therefore, can lead to poor nighttime sleep as well as mental and physical health problems.
As our understanding of circadian health grows, building owners are becoming increasingly interested in it. The key factors are light levels (the amount of light falling on the eye’s photoreceptors throughout the day through vertical illuminance), spectrum (the light wavelength, commonly associated with its color appearance), timing (when the eye receives light), duration (the time span of light exposure), and history (the cumulative occurrence of light and dark patterns received at the eyes over time).
In a traditionally designed interior lighting system, the amount of light delivered is calculated on horizontal surfaces such as desktops. Light-level recommendations are based on vision, and achievable light levels are limited by energy code restrictions on wattage. Spectrum is typically fixed (likely cool white), and occupants receive the same light level all day, unless daylight is available.
In contrast, because light received at the eye stimulates the circadian system, a lighting system that supports the circadian system would provide significant vertical illuminance (light on walls, task lighting, etc.) to ensure a sufficient quantity of light (20–40 foot-candles) falling on the eye’s photoreceptors. Controls would gradually lower the light levels and shift color appearance from cool to warm throughout the day to entrain the occupants’ circadian systems. Ideally, the occupants would have access to daylight.
Circadian lighting and hospitals
Mariana Figueiro, professor and director of the LRC at Rensselaer Polytechnic Institute in Troy, N.Y., is one of the leading researchers in the country on circadian lighting. The LRC recently expanded LightingPatternsforHealthyBuildings.org to include designs for healthcare facilities based on the CS metric and the online tool it developed to evaluate design effectiveness. It has conducted a significant amount of research into the relationship between light and health, most recently involving an installation of circadian lighting at Mount Sinai Health System in New York City, which showed promising early results.
In some respects, designing lighting for vision and CS in a hospital is the same as any other application, such as an office. The Illuminating Engineering Society recommends daytime light levels of 50 foot-candles on the workplane for general tasks in both applications. The lighting should deliver a CS greater than 0.3 during the day, particularly early in the day.
Unlike most offices, hospitals work 24/7, and their populations include both workers and patients. Some of these workers put in long hours, including night and rotating shifts, and exposing patients 24/7 to the same interior lighting disrupts their circadian rhythms. Therefore, the lighting in healthcare facilities must be flexible to meet diverse needs.
Night lighting can be particularly challenging because it must allow patients to sleep while staff work.
High CS during the day and low CS in the evening should be the basis of the design. Additional layers of light can accommodate critical visual tasks and increase alertness in nightshift workers.
This nurse’s station is illuminated for optimal circadian entrainment in the morning (left) and night (right), in this scenario using color-tunable lighting.
The healthcare designs on the Lighting Patterns for Healthy Buildings website cover three distinctive applications: patient rooms, a nurse’s station and a neonatal intensive care unit (NICU).
The NICU requires careful light zoning to serve two unique populations. One is premature infants, who at a certain point in their development can benefit from receiving at least two hours of CS in the morning. The other is nursing staff, who require lighting for circadian health and alertness throughout their shift.
Nurse’s stations also require flexibility. These spaces support day and night shifts, which have different lighting needs. During the day, the lighting should be designed for CS to promote alertness. At night, it should avoid circadian disruption for patients (by providing low CS) while promoting alertness and providing sufficient light for staff to complete work.
An alternative would be to install dimmable and color-tunable linear LED overhead luminaires and wallwashers.
Patient room lighting should provide high CS during the day and low CS in the evening. Night lighting should support patient sleep while accommodating visitors and staff tasks.
Lighting for healthy buildings
In a short time, the lighting community went from a basic understanding of lighting and health to equipment, metrics and design templates suitable for many applications, including hospitals.
Figueiro said circadian lighting is actionable and likely to trend further as resources and research strengthen over time. She encouraged electrical contractors to familiarize themselves with new products and techniques.
“The technology now exists to develop more individualized solutions for healthcare applications,” she said. “Think beyond the ceiling.”
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