Blue Light Can Improve Sleep, Help Brain Recover from Injury

According to a University of Arizona (UArizona) study, exposure to blue light in the morning could re-entrain the circadian rhythm and improve sleep problems, leading to faster recovery from brain injury. Research has shown that the brain repairs itself during sleep. The UArizona team sought to determine whether improved sleep could lead to a faster recovery from mild traumatic brain injury (mTBI).

Research technician Cami Barnes tests a blue light device. Courtesy of William “Scott” Killgore.

In a randomized clinical trial, adults with mTBI used a cube-like device that shined blue light with a peak wavelength of 469 nm at them from a desk or table for 30 minutes early each morning for six weeks. Control groups were exposed to bright amber light. Compared to the control groups, participants exposed to morning blue light experienced phase-advanced sleep timing, falling asleep and waking an average of one hour earlier than before the trial. They were less sleepy during the daytime and their executive functioning was improved. Blue light recipients also showed an increase in volume in the pulvinar nucleus, an area of the brain responsible for visual attention. Neural connections and communication flow between the pulvinar nucleus and other parts of the brain that drive alertness and cognition were also strengthened.

“We think we’re facilitating brain healing by promoting better sleep and circadian alignment, and as these systems heal, these brain areas are communicating with each other more effectively,” professor William D. “Scott” Killgore said. “That could be what’s translating into improvements in cognition and less daytime sleepiness.” According to Killgore, about 50% of people with mTBI also complain that they have sleep problems after an injury.

Killgore said that when it comes to light therapy, timing is critical. “Blue light suppresses brain production of a chemical called melatonin. You don’t want melatonin in the morning because it makes you drowsy and prepares the brain to sleep. When you are exposed to blue light in the morning, it shifts your brain’s biological clock so that in the evening, your melatonin will kick in earlier and help you to fall asleep and stay asleep,” he said.

The researchers plan to continue their work to see if blue light improves sleep quality and how light therapy could affect emotional and psychiatric disorders. Killgore believes that most people, whether injured or healthy, could benefit from correctly timed morning blue light exposure, a theory he hopes to prove for certain in future studies.

The research was published in Neurobiology of Disease (www.doi.org/10.1016/j.nbd.2019.104679).