TORONTO ― Patients with a mild traumatic brain injury (mTBI) who are exposed to blue light experience less depression and fewer cognitive and other concussion-related symptoms than those exposed to a placebo light, a new study has found.
Exposure to blue light in the morning through a special device may be a "critical factor" in resetting the circadian rhythm and helping people who have suffered a concussion, author William D. "Scott" Killgore, MD, professor of psychiatry, psychology, and medical imaging, the University of Arizona College of Medicine, Tucson, told Medscape Medical News.
"This is very new, so I wouldn't say it's the treatment of choice, but we should start looking at using this system as a nonpharmacologic way to perhaps help patients recover faster from a concussion," he said.
The findings were released March 2 ahead of the study's presentation at the upcoming American Academy of Neurology (AAN) 2020 Annual Meeting.
About half of patients with a concussion experience sleep problems, including problems falling asleep, staying asleep, and waking up in the middle of the night, said Killgore.
Poor sleep interrupts the brain's repair mechanism, he said: "Sleep is important for cleaning out the neurotoxins that build up in your brain during the day."
Sleep also helps build oligodendrocyte precursor cells that provide insulation around nerve cells, he added.
Blue light stimulates receptors in the back of the retina that respond only to this wavelength of light, said Killgore. "It specifically projects to an area in the hypothalamus ― essentially the brain's master clock ― that regulates your sleep-wake schedules. So exposure to that bright light essentially resets your circadian rhythm."
That master clock involves regulating the brain's production of melatonin. Morning exposure to blue light shifts that production to facilitate sleep at the appropriate time.
The ideal time to be exposed to blue light is from about 8:00 to 11:00 AM. "Timing is critical," said Killgore. "If you get light at the wrong time, it will reset your circadian rhythm in the wrong direction."
Previous research has shown that exposure to blue light leads to improved sleep, which is widely believed to lead to improved mood.
A separate study conducted by Killgore and colleagues that involved another group of mTBI patients was recently published in Neurobiology of Disease and was reported by Medscape Medical News. That study showed that the participants who received blue light experienced a shift in circadian timing of about an hour. "They were going to sleep an hour earlier and waking up an hour earlier," said Killgore.
The blue light also appeared to change brain structure and brain function, among other things, he said.
The current study included 35 patients who had suffered an mTBI within the previous 18 months. Most injuries were sports related and occurred while playing football or soccer or riding a bike.
Participants were randomly assigned to use a device fitted with a blue LED light (peak wavelength, 469 nm) or one fitted with an amber-colored LED light. They were instructed to use the device every morning for 30 minutes within 2 hours of waking.
The blue-light group comprised five men and 12 women (mean age, 25.5 years). The amber-light group comprised eight men and 10 women (mean age, 26.3 years).
Researchers told participants only that the study was exploring various aspects of light. "Subjects didn't know if they were getting a control or active device," said Killgore.
Researchers used the Beck Depression Inventory (BDI) to evaluate depression symptoms and the Rivermead Post-Concussion Symptom Questionnaire (RPCSQ). This 16-item questionnaire assesses symptoms in the acute stage as well as those that are more chronic.
After 6 weeks, the blue-light group had lower scores on the BDI compared to the amber-light group (P = .005).
"We found that in the amber-light group, there was essentially no change in terms of depression," said Killgore. "But those who got the blue light showed a significant reduction in depressive symptoms, about a 22% decline overall relative to baseline, so a nice drop in overall depression."
Changes in BDI scores were significantly positively associated with changes in the total chronic symptom score (P = .002) in the blue-light group but not the amber-light group. "Those who got blue light showed a significant reduction in the number of symptoms associated with concussion whereas those who got the amber light stayed the same," said Killgore.
There were similar findings for somatic symptoms, such as headache and pain (P = .031), and for cognitive symptoms (P = .014) in the blue-light group.
"These subjects were having fewer problems remembering and paying attention, so their concentration seemed to be improving, at least subjectively," commented Killgore.
There was no significant benefit from the blue light for emotional symptoms. "There was a decline, but it wasn't statistically significant, even though there was a decline in depression," said Killgore.
This, he explained, could be due to the small sample size and the greater sensitivity of the BDI for emotional symptoms relative to the RPCSQ. "The BDI has 21 items that are all focused on aspects of depression, whereas the RPCSQ only asks one item for depression and one item for irritability/anger."
Less Daytime Sleepiness
The researchers also found a significant improvement in daytime sleepiness. "Subjects were much less sleepy by the end of the study if they got blue light than if they got amber light," said Killgore
Participants wore an actigraphy device that took sleep measurements. Early results indicate that blue-light recipients were getting more sleep by the end of the study.
Researchers are now analyzing additional data to see whether the improvements in depression and post-concussion symptoms are linked to improved sleep. They also gathered data from brain imaging that will be analyzed at a later date.
Killgore and his colleagues aim to determine what distinguishes people who respond to blue-light therapy from those who don't. "We want to know what it is that would allow some people to be more responsive than others, so we're going to be exploring skin color, eye color, genetic factors, and other factors," he said.
They're also conducting a study of blue-light therapy in patients with posttraumatic stress disorder, 90% of whom have sleep problems.
"This is quite fascinating," said Killgore. "It looks like if you get blue light after your treatment, the treatment sticks better than if you didn't get the blue light. We think that sleep is probably playing an important role in that."
Several light devices are available, ranging in price from about $100 to $200.
Commenting for Medscape Medical News, concussion expert Frank Conidi, MD, director of the Florida Center for Headache and Sports Neurology, Port St. Lucie, said the study is interesting from a number of perspectives.
For one thing, it shows that blue-light therapy "provides an inexpensive and minimally invasive way to treat concussion," he said.
Conidi said he would recommend blue-light therapy for concussion patients. "I could see neurology practices offering the device to patients as an in-office treatment or to take home for a small fee. I think athletes would be quite receptive to this, as they're always looking for nonpharmacological ways to treat concussion."
Conidi noted that the new results are consistent with other studies that show that decreased depression and improved sleep help with somatic symptoms.
From a research perspective, the study provides a "stepping stone" for larger trials, said Conidi. He would like to see more studies of acute concussion, such as studies as to whether the therapy shortens the duration of symptoms.
"I would also like to see controlled studies on headache and vestibular symptoms, which are the two most common," he said.
The study was funded by the US Department of Defense. Killgore and Conidi have disclosed no relevant financial relationships.
American Academy of Neurology (AAN) 2020 Annual Meeting. Abstract 5363.
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Cite this: Blue Light Improves Concussion Symptoms - Medscape - Mar 02, 2020.