Blue light, or light that exists at wavelengths between 380 and 500 nanometers, has a complicated reputation. The sun gives off blue light. So do TV screens and smartphones, as well as energy-efficient lighting. Discussions about blue light are often framed around how using our personal devices at night disrupts our sleep patterns, fooling the eye and thus the brain into believing the sun is still out. The result is less, worse sleep. Some studies have linked the use of blue light at night to, among other things, cancer, diabetes, and heart disease.
However, there's another dimension to harnessing blue light; a bright side, if you will. New research from the University of Arizona suggests that for those with mild traumatic brain injuries (mTBI), exposure to blue light in the mornings can help speed recovery.
Mild traumatic brain injuries, or concussions, are more common than you might think. People commonly get mTBI from events where the head takes a hard knock or jolt. Fights, falls, car accidents, or playing contact sports can all lead to mTBI, as can experiencing explosive blasts, as in a war. Sometimes there is a period of unconsciousness or "seeing stars," but sometimes a person stays completely conscious the entire time, seeming to "walk it off." Thus, not everyone with a concussion even knows that they have one.
There are, however, a number of signs, both immediate and long-terms. Those with mTBI can find themselves suffering from headaches, memory loss, concentration issues and mental fogginess, irritability and other personality changes, depression, and disturbances to sleep. Few effective treatments exist, which is why the U.S. Army Medical Research and Development Command funded the University of Arizona study.
“About 50% of people with mTBI also complain that they have sleep problems after an injury,” said lead author William D. "Scott" Killgore. Knowing that recent research suggests the brain repairs itself primarily during sleep, Killgore and his team set out to try to improve patients' sleep patterns. Their tool of choice? Blue light.
For 30 minutes each morning for six weeks, a group of adults with mTBI sat at their desks or tables with a cube-like device that emits bright blue light. The light helped dispel melatonin, a chemical that makes you tired and prepares the brain for slumber. "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," explains Killgore.
Patients exposed to 30 minutes of blue light in the morning slept better, falling asleep about an hour earlier and feeling more alert in the daytime. When it comes to brain processing, their speed and efficiency improved, and their brains showed an increase in volume in the pulvinar nucleus, an area related to visual attention.
“When it comes to light, timing is critical," says Killgore. "Light is not necessarily good or bad in-and-of-itself. Like caffeine, it all comes down to when you use it. It can be terrible for your sleep if you’re consuming coffee at 10 o’clock at night, but it may be great for your alertness if you have it in the morning.”