How tunable white light helps patients heal

Tunable white light is still fairly new technology, yet extensive research already emphasizes its ability to help regulate the human circadian rhythm, in turn promoting wellness or healing. This has to do with the human body’s ability to detect and respond to changes in color temperature and intensity that occur naturally in daylight.

Hospitals and other health care facilities can realize significant patient health applications and benefits by incorporating tunable LED lights and lighting controls. Read on to learn about the science behind tunable white light and how you or your hospital can maximize its healing power.

The many shades of white light

The term “white light” actually includes multiple shades of white light, because the color of white light can be described on a subjective basis using the color spectrum. It can also be measured objectively by its correlated color temperature (CCT), measured in Kelvin (K).

The spectrum of color temperatures for white light runs from below 2700K to above 5000K:

• 2700K – established CCT value for the warm, yellowish light emitted by an incandescent lamp
• 5000K – generally regarded as the color of noontime daylight, when the light is most intense

Most lighting sources emit light in a single color. However, the white light output color of an LED can now be tuned such that a single fixture can emit light across the spectrum from 2700K to 6000K. This is made possible because manufacturers can design individual LED chips to emit light at any unique color temperature.

How tunable LED lights work

In color-tuning light fixtures, LED chips with different color temperatures are combined within the single fixture.

For example:

• One fixture may include LED chips rated to produce 2700K light alongside LED chips rated to produce 6000K light.
• If the 2700K chips receive all the power, the tunable LED light will produce 2700K light.
• If the 6000K chips receive all the power, the fixture will produce 6000K light.
• If the different colored chips receive various levels of power, the output of the color temperatures will blend. For example, if the 2700K chips receive 75 percent of the power and the 6000K chips receive the remaining 25 percent, the result will fall somewhere on the white light spectrum between 2700K and 6000K.

Using tunable white light to regulate circadian rhythms

The human body is designed to detect and respond to changes in color temperature and intensity that occur naturally in daylight throughout the day. These environmental cues activate crucial internal processes called circadian rhythms. Circadian rhythm disruption, on the other hand, can increase the risk of a cardiovascular event, obesity, diabetes and neurological problems, including depression.

When people, such as inpatients in a hospital facility, spend more time indoors, white color tuning can combat this circadian rhythm disruption by allowing the built environment to mimic the presence of daylight and the natural cycle of the sun.

The color temperature of daylight changes throughout the day:

• Between 6 a.m. and 9 a.m., daylight is often between 3000K and 4000K.
• By noon, the color temperature of the daylight has shifted to between 5000K and 6000K.
• Color temperature returns to the 3000K to 4000K range by mid-to-late afternoon.

Tunable LED lights may be capable of matching this color-tuning schedule to which the human body is naturally synced.

Tunable white light is designed to maintain the blackbody locus as the Kelvin temperature changes from a warm to cool CCT, a value that indicates the apparent warmth or coolness of light emitted by a source. Some tunable lights allow a limited selection of CCTs, while others allow an infinite number of options. Tunable white light makes it possible to closely match natural light, taking advantage of the resulting health benefits. It also allows facilities to maximize daylight harvesting efforts for energy savings.

Harnessing the power of tunable LEDs

Tunable white lights with lighting controls are becoming much more affordable as a complete package, and today, most LED lights have at least some tuning capability. Recent research and trial installations are beginning to indicate certain health benefits of controlling the spectral distribution of light. This makes tunable white lighting more attractive than ever for hospitals and health care facilities. For example, some hospitals are experimenting with tunable LEDs on geriatric floors and other units to positively affect circadian rhythm.

On a final note, while it is possible to grant users in these buildings individual control — for example, patients or nursing staff — most experts recommend automated systems for a less disruptive, more natural experience. Increased flexibility can lead to unwanted results; luckily, quality architects, engineers and lighting designers understand how to harness this technology to provide the right balance.