Hearing loss could soon be a thing of the past after two new studies have brought scientists a step closer to developing a pill that may prevent noise-induced, and maybe also age-related hearing loss in humans.
In the studies, scientists found that vitamin supplements prevented hearing loss in laboratory animals.
The supplements used in the studies are composed of antioxidants - beta carotene and vitamins C and E - and the mineral magnesium.
When administered prior to exposure to loud noise, the supplements prevented both temporary and permanent hearing loss in test animals.
"What is appealing about this vitamin 'cocktail' is that previous studies in humans, including those demonstrating successful use of these supplements in protecting eye health, have shown that supplements of these particular vitamins are safe for long-term use," said senior author Colleen Le Prell, Ph.D., a researcher at the University of Florida.
In the first study, UF, University of Michigan and OtoMedicine scientists gave guinea pigs the vitamin supplements prior to a four-hour exposure to noise at 110 decibels, similar to levels reached at a loud concert.
Researchers assessed the animals' hearing by measuring sound-evoked neural activity and found that the treatment successfully prevented temporary hearing loss in the animals.
In humans, temporary noise-induced hearing loss, often accompanied by ringing in the ears, typically goes away after a few hours or days as the cells in the inner ear heal.
Because repeated temporary hearing loss can lead to permanent hearing loss, the scientists speculate that prevention of temporary changes may ultimately prevent permanent changes.
In the second, related study in mice, UF, Washington University in St. Louis and OtoMedicine researchers showed that the supplements prevented permanent noise-induced hearing loss that occurs after a single loud sound exposure.
The researchers found that the supplements prevented cell loss in an inner ear structure called the lateral wall, which is linked to age-related hearing loss, leading the scientists to believe these micronutrients may protect the ear against age-related changes in hearing.
"I am very encouraged by these results that we may be able to find a way to diminish permanent threshold shift with noise exposure." said Debara Tucci, M.D., an associate professor of surgery in the otolaryngology division at Duke University Medical Center.
If the trials show that the vitamins are as effective in preventing noise-induced hearing loss in humans as they have been in animals, Le Prell and Miller envision an easy-to-use supplement that could come in the form of a pill for people headed to a rock concert, a daily supplement for factory workers or a nutritional bar included in soldiers' rations.
The findings have been reported at the Association for Research in Otolaryngology's annual conference in Baltimore.