Presbycusis is
Age-Related Hearing Loss
Age related hearing loss, also called presbycusis in the
medical community, is the extremely common phenomenon of the gradual loss of
hearing as we get older. In fact, it’s the most common sensory problem that exists and is an ‘inevitable’ result of
aging, meaning that we will all experience some degree of hearing loss as we
age.
This hearing loss begins as early as the late 20’s with a small loss of
the ability to hear higher tones, and continually deteriorates into advanced
age where many of the aged have difficulty understanding speech.
When Does Presbycusis Begin?
While loudness is measured in decibels, the 'pitch' of sounds are measured in ‘kilohertz’, and young people can hear in a range of about 2-20 kilohertz. Adults gradually lose the higher tones, with those over the age of 25 only able to hear high tones up to about 16 kilohertz, and the elderly unable to hear above 11 or 12 kilohertz, a loss of almost 50% of their hearing.
Interestingly, sound-induced hearing loss erodes the lower tones, making it easy for doctors to distinguish between the two most common types of hearing loss. Unfortunately for those exposed to excessive noise pollution, they will lose both the lower tones and higher tones of hearing as they age.
"Left Untreated, presbycusis of a moderate or greater
degree affects communication and can contribute
to isolation, depression, and, possibly, dementia."
Age Related Hearing Loss
This loss of higher tones even in young adulthood is generally not noticed by the person or those around them, but this loss of high tone, above about 16 kilohertz, definitely occurs. This fact was capitalized on recently by a Welsh security company who successfully deterred teenagers from loitering out front of a client’s business by broadcasting an ‘ultrasonic teenager repellant’, an annoying high-pitched tone, outside of the business.
Unfortunately, teenagers have ‘turned the tide’ on the adults and now have ringtones for their cell phones, based on this concept, that they can hear but their parents and teachers cannot (1), often bypassing bans on cell-phones in the classroom.
How Does Age Related
Hearing Loss Occur?
Studies from around the world seem to show little difference in rates of hearing loss, ruling out genetics as a cause of this problem(2), and there are no known treatments to prevent or delay the condition at this time.
There are several reasons why hearing loss occurs as we age, all include degeneration of one or more of the following structures in the hearing system.
- Stria vascularis- a specialized type of skin cell in the ear
- Spiral ganglion cells- nerve cells that help to conduct sounds
- Inner hair cells
- Outer hair cells(3)
There are aspects of degeneration of both structures that conduct sounds, as well as degeneration of the nerves required to get the conducted sounds to the brain. As a result, presbycusis is often called ‘sensorineural’ hearing loss.
Despite the fact that these degenerative changes have been observed in many studies, no one has actually determined why these changes occur. One theory, however, is the Oxidative Stress Theory of Hearing Loss that was tested in the study Mitochondrial DNA Deletions Associated With Aging and Presbyacusis.
Oxidative stress is the underlying biological condition that causes the ravages of aging, and this might cause the degeneration of the tissues that contributes to this hearing loss. Certain drugs, too, can lead to drug-induced otoxicity at high levels, and may contribute to lower level hearing loss due to oxidative stress over time.
But still, the exact cause or causes of age-related hearing loss are still unknown and therefore, at this time, there is no way to prevent it except to protect the hearing, as much as possible, from noise-related hearing loss that can cause worsening hearing loss with age.
Sources:
- A Ring Tone Meant to Fall on Deaf Ears
- Incidence of presbycusis in Seoul, Korea
- Presbycusis: A Human Temporal Bone Study of Individuals With Downward Sloping Audiometric Patterns of Hearing Loss and Review of the Literature
