When you picture a hospital room in your mind’s eye, it’s bound to appear in sterile, bright tones. But the electric lighting responsible for that can have a negative effect on healing, says Mariana Figueiro, director of the Lighting Research Center at Rensselaer Polytechnic Institute in Troy, N.Y. Emotional well-being and the immune system are both closely tied to circadian rhythms, a roughly 24-hour clock in the human body that is wound, ultimately, by light.

Figueiro’s research over the past 20 years shows that lighting can be a powerful ally in clinical care, especially for patients prone to sleep problems. Timed periods of bright light, for example, can help Alzheimer’s patients regulate when and how much they sleep, increasing their wakefulness during the day and easing their depression and agitation. Recently, Figueiro collaborated with researchers at the Icahn School of Medicine at Mount Sinai in New York City on using bright lights to ease the side effects of cancer treatment.

Q: In the cancer trial, what role did lighting play?

A: We worked with people who had received stem cell treatment for myeloma or lymphoma, which are cancers of the lymphatic system. These patients are typically in the hospital for two to three weeks, and like all hospitalized patients, they get the same level of artificial light at all hours of the day and night. This lack of a robust, daily light-dark pattern can disrupt their circadian cycle, leading to sleep and mood problems that can impede their recovery in the long term.

So we placed light fixtures in their rooms to deliver ambient light at the wavelengths and amounts—brighter in the morning and dimmer at night—needed to synchronize their systems. Our preliminary data show that those who received treatment were less likely to develop depression, had reduced fatigue and maintained their sleep quality during treatment. Good sleep is very important, because we know that it reduces inflammation and bolsters your immune system. 

Q: Is artificial lighting a common factor in depression?

A: Reduced exposure to natural light seems to magnify a lot of existing problems, such as the sleep disruption that can come with Alzheimer’s or, yes, a tendency to suffer from mood disorders or seasonal depression. If you already suffer from circadian disruption, perhaps as a shift worker, you’re going to be sleeping and awake at odd times, so there’s a likelihood you’re getting light at the wrong time. Many studies have shown that these populations are more at risk for depression.

Q: What lighting challenges exist in a health care environment?

A: The default setting is a constant level of brightness, 24 hours a day. It’s a kind of white noise. There’s a conflict, of course, because nurses and doctors need to see, while patients need to sleep. Yet frail people need to be exposed to a robust dark-light pattern. And neither patients nor staff have easy control over the different kinds of light they might need, either to sleep or to work.

Q: Is the technology getting better?

A: The new generation of light-emitting diode lighting has been great because these systems are very adjustable, effective and less expensive to run over time. LEDs let you light up an entire room with varied colors, wavelengths and intensity. You might adjust the light to a hue that helps the eye distinguish colors, which could help hospital staff make accurate visual diagnoses, then adjust levels to help patients sleep better—and do it all wirelessly.

Light manufacturers are also creating portable devices that allow you to measure the light spectrum wherever you are. At Rensselaer we’ve also come up with a circadian stimulus calculator so installers can calculate how much circadian-effective light people are already getting in a given place.

Q: What other health applications are you researching?

A: We’re looking at metabolic disorders, which get in the way of how the body produces or processes energy. We started with mice, and have already shown that the patterns of light and dark that we associate with shift work can cause circadian disruption and decrease glucose tolerance. We’re also testing long-wavelength red light, which has been shown to increase nighttime alertness, in nurses who do shift work.

My newest project is working with people who have suffered traumatic brain injury, which brings a high risk of developing a sleep disorder. The light for the control group is the usual dim and dingy setup, while our other subjects get bright ambient light. When I came in to check one installation, a patient told me, “I absolutely love these lights. I suffer from depression, and when those lights turn on I feel like a different person.”