Near Infrared Light Directed Into the Ear Aids Against Hearing Loss

A new treatment for preventing hearing loss, or restoring damages, involves shooting a beam of infrared light down the patient's ear, and ongoing US trials show promise.

University of Miami researchers are behind an ongoing clinical trial assessing the efficacy of infrared light beamed into the ear against the detrimental effects of noise exposure. Together with the Office of Naval Research, the ongoing trial for noise exposure and Near Infrared (NIR) Light aims to gather more insights on the effects of noise on the auditory system, in terms of health and performance, and how therapy procedures like NIR light can mitigate its effects.

Apple CEO Tim Cook Visits California School For The Deaf In Fremont, California — FREMONT, CA - MAY 17: Actor, model, and activist for the deaf community Nyle DiMarco speaks to students at the California School for the Deaf on May 17, 2018 in Fremont, California. Apple CEO Tim Cook and DiMarco visited students at the school on Global Accessibility Awareness Day to kick off the Everyone Can Code program that Apple is bringing to the California School for the Deaf and other schools for deaf and blind/low-vision students. Photo by Justin Sullivan/Getty Images

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Harm of Regular Noise Exposure

Noise-Induced Hearing Loss (NIHL) is one of the main causes of hearing loss, with the Centers for Disease Control and Prevention (CDC) reporting about 40 million adults in the US aged 20 to 69 suffering from this condition.

Humans are born with auditory hair cells, although these are relatively small compared to other species. On average, we have about 15,000 of these thin structures in each ear. These cells convert sound vibrations in the air to electrical signals that are carried by the auditory nerve and to the brain where these impulses are processed.

Like any other cells in the human body, auditory hair cells decline with age, suffer from diseases, and get harmed by regular exposure to loud noise. Noise, particularly, causes the cells to get "overworked" and end up being damaged. Unfortunately, these auditory hair cells don't regenerate once totally damaged, once they're killed, they're gone for good.

Potential Cure for Hearing Loss

While there is no currently available treatment for hearing loss, a growing body of studies has focused on NIR light. Over the previous decade, studies have shown the benefits of NIR light and low-power light therapy for wound healing and rehabilitation. Now, researchers are looking at whether similar benefits apply to hearing loss.

A recent study published last year in the journal PeerJ demonstrates the benefits of using NIR light against hearing loss in mice. The subjects were treated with a near-infrared light for ten minutes before researchers exposed them to loud noise.

Researchers found that mice with the NIR treatment experience less hearing loss compared to the untreated ones.

"Our results suggest that a single NIR pre-treatment induces a very effective protection of cochlear structures from noise exposure. Pre-exposure of 10 min seems to emerge as the optimal dosage for our experimental setup," researchers from the Charite Medical School and Advance Bionics, both in Germany, wrote in their paper (Near-infrared-light pre-treatment attenuates noise-induced hearing loss in mice).

An older study, published in 2012 in the Journal of Biomedical Optics, demonstrates that near-infrared light used in treating mice resulted in more hair cells and a marked improvement in their hearing ability compared to those that did not receive the treatment.

While the effects of near-infrared light have been observed, its exact mechanism remains unclear. One theory proposes that a protein called cytochrome c oxidase leads to stimulated production of adenosine triphosphate (ATP), which has been shown to reduce cell mortality rates and encourage repair processes.