86 percent of the people exposed to bright white light had normal sleep efficiency. (Photo: Pixabay)
Cancer survivors often suffer from chronic fatigue, and when they do, a new study suggests that waking up to bright white light may help them sleep better.
For the month-long study, researchers had 44 cancer survivors sit very close to a light box early every morning for 30 minutes. The patients were randomly assigned to therapy with either bright white light or dim red light.
More than half of the participants suffered from what’s known as poor sleep efficiency, a measure of how much time in bed people spend asleep. After a month of treatment, however, 86 percent of the people exposed to bright white light had normal sleep efficiency, while 79 percent of the people exposed to dim bright light still had poor sleep efficiency.
It’s possible that the bright white light helps cancer survivors reset their internal clocks, or circadian rhythms, so that their body can more easily rest at night and wake during the day, said study leader Lisa Wu of the Northwestern University Feinberg School of Medicine in Chicago and the Icahn School of Medicine at Mount Sinai in New York City.
"Cancer survivors and even other individuals who spend most of their days indoors may not receive enough bright light to keep their biological rhythms synchronized," Wu said by email. "Given that light exposure from being outside is generally much brighter than light received indoors, the addition of artificial bright light each morning helps cancer survivors reduce fatigue and improve their sleep quality by strengthening their circadian rhythms."
Beyond just improving sleep efficiency, bright white light was also associated with medium to large improvements in sleep quality, total sleep time and wake time, researchers report in the Journal of Clinical Sleep Medicine.
When researchers checked back with participants three weeks after they stopped light therapy, improvements in sleep quality associated with bright white light had disappeared, and this group no longer fared better than people who had been exposed to dim red light.
This suggests that ongoing therapy may be needed for cancer survivors to experience a sustained improvement in sleep.
Beyond its small size, another limitation of the study is that the cancer survivors were screened only for cancer-related fatigue and not for sleep disorders, the authors note.
One strength, however, is the inclusion of people with different types of cancer, including blood malignancies, breast tumors and gynecological cancers, noted Ilia Karatsoreos of the Sleep and Performance Research Center at Washington State University in Pullman. While some previous studies have found similar results with bright light therapy for cancer survivors, research to date has focused mostly on breast cancer, Karatsoreos, who wasn’t involved in the study, said by email.
"What is new about this study is that it demonstrates that there is potential for the use of bright light therapy to improve fatigue in many different types of cancer, suggesting that potentially the underlying mechanisms are similar in different disease states," Karatsoreos said.
Even without a light box, people may get enough bright light outdoors and they may also improve sleep by eating well and exercising regularly, noted Frida Rangtell, a sleep researcher at Uppsala University in Sweden who wasn’t involved in the study.
"If patients do not have access to a light box, going outside and getting natural light exposure in the morning or during the day can exert similar effects," Rangtell said by email. "If this is not possible, it could be good to at least be as close to a window with natural light exposure as possible, and keep the indoor lighting as bright as possible during the morning."