A recent discovery by scientists that birds do not lose their hearing as they age could lead to more effective treatments for deafness in the elderly. German researchers from the University of Oldenburg found that barn owls have ‘ageless ears’.
This genetic advantage means that the hearing cells in the birds can regenerate, unlike those in humans, which die off with old age. It is only the second study of its kind to have been carried out, but the first, which was conducted on starlings, returned the same result.
Dr Ulrike Langemann, of the University of Oldenburg, said: “Barn owls have ageless ears - evolution has favoured birds to benefit from regeneration in the inner ear that is absent in mammals.
“Mammals, including humans, commonly suffer from a serious hearing loss at old age. If we could learn how birds retain their sensitivity, this may lead to new treatment options for humans.”
She went on to describe the discrepancy in hearing between elderly people and their bird counterparts. By the time a human being turns 65, they will have lost 30 decibels of the sensitivity at high frequencies that they enjoyed in their youth. In comparison, older birds have only minimal hearing loss, if any at all.
The study analysed the hearing of trained barn owls at various different ages and found there was no degradation in the older individuals. Their responses to the sounds of other birds were recorded and these were played at varying frequencies throughout the test.
Another element of the research monitored the hearing of a single barn owl during its lifetime. At the age of 23, the bird showed no signs of deterioration the sense, helping to underscore the findings of the rest of the study.
Dr Langemann believes the cochlea is the key part of the ear that helps them to remain ageless. It is a small structure in the inner ear that resembles a shell and is responsible for relaying sound waves to the auditory nerve, where they are heard as noises.
The cochlea contains hair cells and when these are damaged through loud noises or ageing in humans, the ability to hear diminishes. Since birds can regenerate these hair cells, they are protected from hearing loss.
Such an evolutionary trait is important for birds in the wild, as being unable to hear predators would make older individuals easier targets as prey. While humans have not needed to adapt in such a way, the loss of hearing can have an impact on a person’s quality of life.
The next question for scientists will be how to harness the new knowledge they have about birds’ ageless ears to help find cures for people. While it has not yet sparked any new treatments, it could do in the future.
Dr Langemann summarised: “The hope and interesting question remains whether, someday, our knowledge on preservation of sensitive hearing in birds will provide for new treatment options that could counteract human sensory deficits."