Now Hear This

 Now Hear This

By Peter Galvin, MD

Age-related declines in hearing gradually affect every person during life. A person’s ability to hear depends on the inner ear (cochlea) precisely encoding sounds into neural signals, which are then, via the acoustic nerve, sent to the brain where they are decoded into meaning. A pathologic process may occur at any level of this pathway and adversely affect hearing, but changes in the cochlea are the most common cause of age-related hearing loss. This loss of hearing is characterized by progressive loss of sensory hair cells in the cochlea. Unlike other cells in the body, sensory hair cells in the inner ear cannot regenerate, and these cells are progressively lost over the course of life owing to the cumulative effects of multiple etiologic processes. The strongest risk factors for age-related hearing loss include (of course) older age, lighter skin color (melanin in the cochlea is protective), male sex, and exposure to loud noise. Other risk factors include cardiovascular risk factors such as diabetes, smoking, and hypertension, which can contribute to microvascular injury to the cochlear blood vessels.

Hearing, especially regarding sounds at higher frequencies, begins to diminish in early adulthood. Clinically significant hearing loss increases across the life span, nearly doubling with every decade of life such that two thirds of all adults 60 years of age and older have some form of clinically significant hearing loss. In the U.S. in 2019, approximately 72.9 million, or one in five, persons were estimated to have hearing loss. Studies have shown associations between hearing loss and impaired communication, cognitive decline, dementia, higher medical costs, and other adverse health outcomes. Recent research has focused on the links between hearing loss and cognitive decline and dementia. Because age-related hearing loss occurs gradually and without any clear inciting event, those with it often are not aware of their impaired ability to hear. They often attribute their perceived hearing difficulties to external reasons, for example others not speaking clearly (“You’re mumbling!”) and background noise (high-frequency hearing loss makes it difficult to discern conversation out of background noise).

Hearing loss may be diagnosed and assessed using audiometry, done by an audiologist or ENT physician. There is also a recently adopted consumer technology industry standard for hearing-related technologies (e.g., smartphones and earbuds) that specifies how these applications can directly measure and report to users their PTA4 (also termed “hearing number,” which can be tracked on a regular basis. But the bottom line is that currently there is no technology available to replace lost or damaged cochlear hair cells. Therefore, the management of the condition is focused on protecting what hearing remains and the use of hearing enhancement technologies (hearing aids and cochlear implants). Unfortunately, the prevalence of hearing aid use and cochlear implants among persons that could benefit from the remains very low. In the U.S., among those who would benefit from them, hearing aid use is below 20% and cochlear implantation is less than 5%. Reasons include social stigma, poor accessibility, and the fact that these technologies do not fully restore age-related hearing loss. In 2022, the FDA approved the sale of over-the-counter hearing aids, and their cost is similar to high-quality wireless earbuds ($100 – $300), which increasingly are available with hearing aid technology.

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