Scientists from Massachusetts Eye & Ear led a landmark study that presents a new hypothesis that explains the cause of age-related hearing loss, challenging the current theory that has dominated over 50 years of medical science. The research shows that age-related hearing loss, or presbycusis, is mainly caused by accumulated damage to inner ear sensory hair cells, paving the way for hair-regeneration technologies to offer new treatments.
Previous animal research has shown that presbycusis is caused by a slowly degenerating stria vascularis, a vital part of the cochlea. This is why several scientists assumed that this process applies to age-related hearing loss in humans as well.
The most accurate way to investigate the inner ear of a human is by using autopsied post-mortem specimens. To better comprehend the pathology of presbycusis, the team set out to perform the most extensive analysis of autopsy specimens ever conducted.
The study, published in the journal JNeurosci, recorded the close examination of over 120 human inner ear autopsy specimens. The majority of samples were accompanied by audiogram data collected while the subjects were still alive, allowing the scientists to correlate patterns of hearing loss with the anatomical data accurately. However, the team found that damage to the stria vascularis didn’t connect with the pattern or severity of hearing loss. Instead, the location and degree of hair cell death was the most accurate predictor of hearing loss.
These findings suggest that presbycusis is mainly caused by damage to the sensory hair cells in the cochlea, which implies that age-related hearing loss is not from aging but rather a lifetime of acoustic over-exposure(AOE). “The greater hair cell death in human ears suggest that the high-frequency hearing losses that define presbycusis may be avoidable, reflecting mainly accumulated damage from environmental noise exposures. It’s likely that if we were more careful about protecting our ears during prolonged noisy activities, or completely avoiding them, we could all hear better into old age,” said M. Charles Liberman, the study’s co-author.
Peizhe Wu, the lead author of the study, concluded:
“Our study upends the dogma about the major cause of age-related hearing loss. Documenting the dominant role of progressive hair cell loss in the hearing impairment of normal aging means that the millions who suffer with this condition could benefit from the hair cell regenerative therapies that are the focus of ongoing research across the world.”
These findings drastically expand the potential of future treatments to improve hearing in elderly patients. If presbycusis is caused by hair cell damage, then advances in hair cell regeneration could potentially be repurposed to treat hearing loss.
