Explosions. Jet engines. Bursts of gunfire.
In today’s military, soldiers can be hurt by more than just bullets, and one very sensitive area has been under constant attack—the ears. Even with external hearing protection, the sounds of warfare can damage the sensitive inner ear, or cochlea, and severely reduce hearing.
But a new drug combination, developed through a collaboration between OMRF and the Hough Ear Institute, along with support from INTEGRIS Health, has shown promise in reducing hearing loss. The treatment could have both military and civilian applications.
OMRF’s Robert Floyd, Ph.D., working with Hough CEO and retired Army ear surgeon Richard Kopke, M.D., found that a combination of two compounds—4-OHPBN nitrone and the drug n-acetyl-cysteine—could stop damage to the inner ear caused by acute acoustic trauma.
“This is a very exciting finding,” said Floyd, who holds the Merrick Foundation Chair in Aging Research at OMRF. “The research is still at a pre-clinical stage, but we’re hopeful that we soon can begin testing in humans.”
According to a 2003 study by the Institute of Medicine, “Noise and Military Service: Implications for Hearing Loss and Tinnitus,” hearing loss is the second most common type of disability among veterans, accounting for more than 75,000 cases of disability. “Hearing loss costs the U.S. Department of Defense about $1 billion a year,” Kopke said. “It’s the most common injury for which people are evacuated from a war zone. I’ve known some 30-year-olds who come out of the service with the hearing of a 70-year-old.”
If medics are equipped with the drug combination, he said, they could administer it in the field, immediately after an explosion or other combat situation causes noise damage.
Without the medication, prolonged exposure to loud noise can damage and kill hair cells that register sound, causing hearing loss. But in laboratory animals, the hearing loss was almost completely prevented if the drug combination was given within four hours of exposure to noise levels that would otherwise cause acoustic trauma. Significant decreases were also seen if the combination was administration within 24 hours of exposure.
Current tests are being performed on chinchillas because their hearing range is similar to humans. Electric impulses in the brain are measured to gauge how well the animals hear after taking the drugs.
“If this therapy ultimately proves effective,” said Floyd, “it could also have many civilian applications, including combating age-related hearing loss.” According to a National Health Interview Survey Core, 1 in 3 Americans over the age of 70 reported that they had trouble hearing. And the National Institute for Occupational Safety and Health reports that approximately 30 million Americans are exposed to hazardous noise levels on the job.
The discovery is the product of a four-year collaboration between Floyd and Kopke, whose work was funded by the U.S. Department of Defense Office of Naval Research.