Hearing loss resulting from exposure to loud sounds is very common. Now, researchers say a vitamin supplement may prevent the nerve damage responsible for that loss - even after exposure to the deafening noise.
Millions of people around the world are exposed every day to deafening noises - from explosions to the loud sounds associated with working in construction and airline jobs - and are at risk of losing their hearing.
The sound damages nerves that stimulate the cochlea, a tiny snail-shaped structure inside the ear that transmits audio signals to the brain.
A vitamin supplement, related to the vitamin B3, has been shown to protect the hearing neurons of mice exposed to loud noise. It’s called nicotinamide riboside or NR.
In a study published in the journal Cell Metabolism, researchers at Weill Cornell Medical College in New York and the Gladstone Institutes in California describe how they gave NR to a group of mice exposed to loud noise. NR was administered both before and after the noise exposure, which deafened only the rodents that got the placebo or sham treatment.
“When we gave this compound [NR], it was pretty remarkable," said Samie Jaffrey, a professor of pharmacology at Weill Cornell. "Their hearing was as though they had never been exposed to any noise at all. And we could even give the compound even shortly after noise exposure. And so that was also pretty important because we want to be able to have a therapy that could mimic what would happen to a real person. That is, they get exposed to a real noise and then they need to find some sort of interventions."
Noise-induced hearing loss happens gradually. Jaffrey says there appears to be a delay of a couple of days to weeks between toxic noise exposure and the onset of damage to auditory nerves or neurites.
“The loss of the neurites takes time. And we can intervene with this compound, if we administer it early enough, we can intervene and prevent the degeneration," she said. "And so I think that’s important because that makes it more likely to be useful for people."
Jaffrey says hearing difficulties, involving the same auditory nerve pathway, can be caused by some drugs and age-related diseases, including diabetes and pulmonary hypertension. He says researchers are anxious to see whether NR can also treat hearing loss in those cases.