Study links occupational hearing loss to faster aging of auditory system

Montreal — Noise exposure in the workplace can accelerate presbycusis – the normal loss of hearing as a result of aging – according to a literature review conducted by researchers at the Canadian scientific research organization IRSST.

Researchers looked at 31 human and animal studies published since 2000, and noted a “clearly demonstrated” link between noise exposures and accelerated hearing loss.

Noise exposure disturbs how sensory cells in the inner ear function, the researchers said. Initially, noise exposure causes a temporary and reversible shift in hearing thresholds. After noise exposure stops, the auditory system slowly recovers its initial hearing capacity. However, if noise exposure is “very high,” the recovery can be incomplete. If noise exposure is repeated over time, it can lead to permanent and irreversible hearing threshold changes.

When studies used more sensitive measurements, the researchers said, damage to synapses in the ear can be seen decades before presbycusis normally becomes evident. Workplace exposure to elevated levels of noise can magnify and accelerate this process, the review states.

“A number of authors go as far as to suggest modifications to the classical concept of presbycusis that links this type of hearing loss to aging alone,” Tony Leroux, lead author and professor at the University of Montreal’s school of speech-language pathology and audiology, said in a Nov. 1 press release.