LEDs mimic natural light patterns | The Triangle

LEDs mimic natural light patterns

Drexel University biomedical engineering professor Don McEachron and architecture and interior design professor Eugenia Ellis are developing an LED light fixture that mimics the natural progression of the sun throughout a day. Their plan is to install the fixtures in health care facilities where light will help maintain natural rhythms within the body and ultimately improve the health of residents.

The 2-square-foot fixture will first be tested in St. Francis Country House, a senior living facility in Delaware County, Pa., where it will be placed in corridors and communal dining rooms.

The problem with artificial lighting currently used in care facilities is that it does not cater to natural circadian rhythms of its patients, especially aging ones. Just like any bodily function or process, the circadian rhythm weakens with age. McEachron, research professor and coordinator for academic assessment and quality improvement in the School of Biomedical Engineering, Science and Health Systems, said, “We put [patients] in an environment with virtually no light-dark cycle, thus increasing the chances that their rhythms will become erratic or desynchronized. If we wanted to decrease the quality of their lives, both physiologically and psychologically, we have certainly created the right environment to do it. However, the goal is to improve the residents’ or patients’ lives, not make those lives worse. Human ancestors evolved in an environment with a strong light and dark cycle — it is what the circadian system evolved to expect. While we cannot take aging individuals and put them outdoors in order to expose them to the solar cycle, we can use technology to bring the solar day inside.”

Ellis, an associate professor in both the Antoinette Westphal College of Media Arts & Design and the College of Engineering, is currently building the prototype. She compares the fixture to a stereo sound system — in a good sound system you can hear the music but cannot see the speakers. Ellis explained that though the fixture won’t be seen in the living facility, residents will notice the mimic of colors and intensities of natural sunlight depending on the time of day.

The colors will begin with gold that imitate morning light, progress to bright light with a blue cast, then to amber and eventually red, where it will stay throughout the night. The light fixture will not mimic the weather of a particular day, nor will it imitate the progression of the sun in dark, winter months. The short photoperiod (length of daylight in a 24-hour period) characteristic of winter has been associated with a type of seasonal affective disorder called winter depression, and Ellis and McEachron believe that this type of photoperiod could generate negative effects within the facility. In the event of an emergency, the LED fixtures can be overridden to allow for a safe evacuation of the building with maximum light.

The circadian (Latin for “about a day”) rhythms are natural 24-hour cycles that serve to organize the body’s various activities, McEachron explained. As mammals, humans are equipped with a “master circadian clock” called the suprachiasmatic nuclei, located in an area of the brain called the hypothalamus. This clock is linked to the eye, from which it receives information about light and dark, and to the rest of the body so that rhythmic processes can be controlled appropriately. Among its many functions, the SCN controls the secretion of melatonin from the pineal gland. Melatonin is a hormone that makes humans drowsy, improves sleep and stimulates the immune system. The circadian system is most sensitive to light on the green-blue side of the spectrum. Exposing a human to such light at the correct time of day can assist in synchronizing rhythms; exposure at other times can suppress melatonin secretion, disturbing sleep and inhibiting immune responses.

While the SCN reacts to light on the blue-green side of the visible spectrum, it is relatively insensitive to light in the red part of the spectrum. Red light is still visible but does not significantly suppress the secretion of melatonin. Therefore, the LED light will maintain a red light throughout the night so as to allow staff to be able to see and effectively conduct their work in corridors. Patients will turn off the lights in their individual rooms to complete darkness and will no longer be disturbed by the light coming in through cracks under the door.

Ellis explained, “When you’re young you know your body regulates itself, but as you get older the systems aren’t quite as resilient. So when you become a much older person, your body is much more delicate, and it doesn’t rebound quite as fast. That’s why it’s more important to keep the environment stable in a cyclical rhythm.”

McEachron and Ellis argued that if you can resynchronize and establish rhythm coherence, then cognitive functions will improve. It won’t be a cure, but it will limit stress and the impact of aging on tissue repair, immune functions and other healing processes. This theory extends beyond health care facilities.

McEachron said that students are particularly susceptible to rhythm disruption as well. While younger, with a relatively strong SCN, lighting in residence halls and late-night buildings (combined with energy drinks and other stimulants) disrupts natural circadian rhythms. Just as with nursing home patients, this disruption has a negative effect on cognitive functions.

“Students are following a cycle which is destructive to their ability to learn and maintain their health. What I see happening is that they are putting themselves at risk with these schedules and the lack of sleep they are engaging in. It makes no sense to pay tuition to become educated and then develop a schedule that limits that. I would contend that the schedules that students are keeping are physiologically impairing them from learning,” McEachron said.

McEachron hopes to prove this assertion with studies that will be done in the St. Francis Country House. There, he and Elizabeth Gonzalez, an associate professor and department chair of the Doctoral Nursing Program, will observe the effects of the LED fixture on patient health and recovery.