April 08, 2021
Patients with migraine experienced about a 60% reduction in pain intensity and number of headache days per month after exposure to green light therapy, according to results of a small study from the University of Arizona, Tucson.
"This is the first clinical study to evaluate green light exposure as a potential preventive therapy for patients with migraine, " senior author Mohab M. Ibrahim, MD, PhD, said in a press release. "Now I have another tool in my toolbox to treat one of the most difficult neurologic conditions – migraine."
"Given the safety, affordability, and efficacy of green light exposure, there is merit to conduct a larger study," he and coauthors from the university wrote in their paper, which was published in Cephalgia.
The study included 29 adult patients (average age 52.2 years), 22 with chronic migraine and the rest with episodic migraine who were recruited from the University of Arizona/Banner Medical Center chronic pain clinic. To be included, patients had to meet the International Headache Society diagnostic criteria for chronic or episodic migraine, have an average headache pain intensity of 5 out of 10 or greater on the numeric pain scale (NPS) over the 10 weeks prior to enrolling in the study, and be dissatisfied with their current migraine therapy.
The patients were free to start, continue, or discontinue any other migraine treatments as recommended by their physicians as long as this was reported to the study team.
White Versus Green
The one-way crossover design involved exposure to 10 weeks of white light emitting diodes, for 1-2 hours per day, followed by a 2-week washout period and then 10 weeks' exposure to green light emitting diodes (GLED) for the same daily duration. The protocol involved use of a light strip emitting an intensity of between 4 and 100 lux measured at approximately 2 m and 1 m from a lux meter.
Patients were instructed to use the light in a dark room, without falling asleep, and to participate in activities that did not require external light sources, such as listening to music, reading books, doing exercises, or engaging in similar activities. The daily minimum exposure of 1 hour, up to a maximum of 2 hours, was to be completed in one sitting.
The primary outcome measure was the number of headache days per month, defined as days with moderate to severe headache pain for at least 4 hours. Secondary outcomes included perceived reduction in duration and intensity of the headache phase of the migraine episodes assessed every 2 weeks with the NPS, improved ability to fall and stay asleep, improved ability to perform work and daily activity, improved quality of life, and reduction of pain medications.
The researchers found that when the patients with chronic migraine and episodic migraine were examined as separate groups, white light exposure did not significantly reduce the number of headache days per month, but when the chronic migraine and episodic migraine groups were combined there was a significant reduction from 18.2 to 16.5 headache days per month.
On the other hand, green light did result in significantly reduced headache days both in the separate (from 7.9 to 2.4 days in the episodic migraine group and 22.3 to 9.4 days in the chronic migraine group) and combined groups (from 18.4 to 7.4 days).
"While some improvement in secondary outcomes was observed with white light emitting diodes, more secondary outcomes with significantly greater magnitude including assessments of quality of life, Short-Form McGill Pain Questionnaire, Headache Impact Test-6, and Five-level version of the EuroQol five-dimensional survey without reported side effects were observed with green light emitting diodes," the authors reported.
"The use of a nonpharmacological therapy such as green light can be of tremendous help to a variety of patients that either do not want to be on medications or do not respond to them," coauthor Amol M. Patwardhan, MD, PhD, said in the press release. "The beauty of this approach is the lack of associated side effects. If at all, it appears to improve sleep and other quality of life measures," said Patwardhan, associate professor and vice chair of research in the University of Arizona's department of anesthesiology.
Better Than White Light
Asked to comment on the findings, Alan M. Rapoport, MD, clinical professor of neurology at the University of California, Los Angeles, said research has shown for some time that exposure to green light has beneficial effects in migraine patients. This study, although small, does indicate that green light is more beneficial than is white light and reduces headache days and intensity. "I believe patients would be willing to spend 1-2 hours a day in green light to reduce and improve their migraine with few side effects. A larger randomized trial should be done," he said.
The study was funded by support from the National Center for Complementary and Integrative Health (to Ibrahim), the Comprehensive Chronic Pain and Addiction Center–University of Arizona, and the University of Arizona CHiLLI initiative. Ibrahim and one coauthor have a patent pending through the University of Arizona for use of green light therapy for the management of chronic pain. Rapoport is a former president of the International Headache Society. He is an editor of Headache and CNS Drugs, and Editor-in-Chief of Neurology Reviews. He reviews for many peer-reviewed journals such as Cephalalgia, Neurology, New England Journal of Medicine, and Headache.