Patients in an average hospital room are exposed to so little light during the day that their bodies cannot adopt a normal sleep-wake cycle, a small study suggests.
Researchers found the lowest levels of daytime light exposure were tied to worse mood and more fatigue and pain among patients, compared to those whose rooms were better-lit during the day.
"Until now, no one has looked at the associations among light and outcomes such as sleep, mood and pain experienced in the hospital," said Esther Bernhofer, lead author of the study and a nurse researcher at the Cleveland Clinic's Nursing Institute.
"This study forms a basis for testing future lighting interventions to improve sleep-wake patterns, mood and pain in hospitalized adults," Bernhofer said.
Past research has shown that exposure to light during the day is important for setting the body's internal clock. Too little light and too much - or exposure to light at the wrong times - can affect sleep quality at night and mood during the day.
To see whether light might play a role in hospital patients' healing, Bernhofer and her colleagues gathered data on 40 men and women admitted between May 2011 and April 2012 to a large academic hospital.
The patients wore a wrist device for 72 hours to measure their sleep-wake patterns and light exposure, and completed questionnaires to evaluate their mood and pain levels.
The researchers found that patients were exposed to low levels of light around the clock, including overnight.
And like many hospital patients, those in the study slept poorly, with frequent interruptions and an average of only about four hours of sleep per night. Patients who had less light exposure during the day reported having a more depressed mood and being more fatigued than those exposed to more light.
On average, patients in the study were exposed to only about 105 lux, a measure of light emission in a given area. Normal office lighting provides about 500 lux and a sunny day can represent as much as 100,000 lux.
Past studies have found that a minimum of 1500 lux for 15 minutes per day is necessary to establish a normal sleep-wake cycle but at least 4000 lux over the course of eight hours is preferred for sleep health, Bernhofer's team writes in the Journal of Advanced Nursing.
The results of her group's small study could potentially open the door to simple ways to boost patient well being in the hospital, Bernhofer said.
More research is needed, but "Further findings might result in a cost-effective way to provide supportive therapy for sleep and pain - common issues in hospitalized patients affecting their ability to heal and be well," Bernhofer said.
"These findings are preliminary and should not dictate any policy or practice changes for healthcare institutions until more specific research can be done," Bernhofer added.
Still, there are few risks to exposing a loved one in the hospital to more light during the day, she said.
"It makes sense that if a loved one is recovering, and they can be moved to an area with brighter, more natural light such as that directly in front of a window, that their mood may improve and that they may sleep better," she said.