Noise-Induced Hearing Loss Affects Millions of Americans, Including Children

BUFFALO, N.Y. -- The hearing aids being worn by President Clinton may not greatly improve his ability to understand faint speech, according to a hearing researcher with the University at Buffalo Center for Hearing and Deafness who is an expert on noise-induced hearing loss

"Mild, high-frequency hearing loss reflects underlying damage to the inner ear that interferes with the ability to process signals out of noisy backgrounds," says Robert F. Burkard, Ph.D., UB associate professor of communicative disorders and sciences.

"What Clinton probably needs is something that suppresses background noise. It's possible, but not probable, that hearing aids will help his problem."

Burkard says noise-induced high-frequency hearing loss is endemic in the U.S., and poses a particular problem for children, affecting their ability to achieve in school.

"Many children already have a significant hearing loss, which often means they have a decreased ability to process signals in the presence of background noise," Burkard notes. "Noise levels in classrooms today are unacceptably high, so these children often can't understand what the teacher is saying. It's one of the causes of kids acting out in the classroom."

The hearing loss experienced in old age, which will become an increasingly significant public-health problem as the baby-boom generation becomes a senior generation, is not solely the result of aging itself, Burkard notes, but of the summation of all the noise experienced since childhood.

"Exposure builds up over the years, like a silent poison in your system," he says. "Over time, the exposure can lead to damage, and it almost always starts at the high frequencies."

• 9-12 million people in the U.S. work in settings with dangerous levels of noise.

• Pervasive hazards outside of work include snowmobiles, lawn mowers and personal music systems.

• Some antibiotics and cancer drugs cause hearing loss.

• The aging population will dramatically increase the number of people affected by hearing loss.

Burkard and colleagues with the center are conducting some of the most advanced research currently under way into the science behind, and treatments for, noise-induced hearing loss and deafness.

Donald Henderson, Ph.D., co-director of the center, reported in September at the Inner-Ear Biology Meeting in Bari, Italy, that noise-induced hearing loss may be caused partly by free-radical oxidative damage to sensory cells, and that an antioxidant-enhancing drug called R-PIA can lessen the damage.

In earlier work, involving birds, UB researchers showed that sensory cells in the birds' cochlea, or sensory organ, can regenerate, restoring their hearing. They now are trying to replicate their findings in mammals. Another investigation involves the use of desensitization to prevent hearing loss due to "traumatic" noise.

Richard Salvi, Ph.D., center co-director, has received a grant to search for the site in the brain responsible for tinnitus (persistent ringing in the ears) using positron emission tomography, or PET scans. He also is investigating the apparent ability of some tinnitus suffers to alter the ringing.