New insights in age-related hearing loss

The death of sensory hair cells in the inner ear has long been blamed for age-related hearing loss. However, this may not be entirely true as the role of nerve cells in hearing loss can't be ignored, says a study.

Studies in mice have verified an increased number of connections between certain sensory cells and nerve cells in the inner ear of ageing mice.

Because these connections normally tamp down hearing when an animal is exposed to loud sound, the scientists think these new connections could also be contributing to age-related hearing loss in the mice, and possibly in humans.

"The nerve cells that connect to the sensory cells of the inner ear are known to inhibit hearing, and although it's not yet clear whether that's their function in older mice, it's quite likely," said Paul Fuchs from Johns Hopkins University School of Medicine.

"If confirmed, our findings give us new ideas for how physicians may someday treat or prevent age-related hearing loss," he added.

The study was published in The Journal of Neuroscience.

Previous research has suggested that with age, inner hair cells in mice and humans experience a decrease in outgoing nerve cell connections, while incoming nerve cell connections increase.

To find out if the new connections worked, the researchers recorded electrical signals from within the inner hair cells of young and old mice.

They found that the incoming nerve cells were indeed active and that their activity levels correlated with the animals' hearing abilities: The harder of hearing an animal was, the higher the activity of its incoming nerve cells.

If the same phenomenon occurs in human ears, Fuchs said there may be ways of preventing the incoming nerve cells from forming new connections with inner hair cells, a technique that could help maintain normal hearing in old age.