By Dr. Gary L. Deel
Faculty Director, Wallace E. Boston School of Business, American Public University
One of the classes in American Public University’s Psychology program — Perception — covers the effects of presbycusis in interactions with our environment. Presbycusis is the gradual loss of hearing. It is linked to natural aging and degradation of bodily systems. According to the Cedars-Sinai Health Library, an estimated 30% of humans over the age of 65 have experienced some level of presbycusis.
How Does Hearing Work?
The process of normal human hearing is a complex collaboration of many intricate and specialized parts, all working together to receive and interpret sound waves. The outer, visible structure of the ear is called the pinna. Once sound waves travel through the pinna, they enter the auditory canal, a tube-like structure that connects to the eardrum (also known as the tympanic membrane, akin to a drum head). There is a resonance effect that occurs in the auditory canal and this enhances the sound intensity that we hear.
When sound waves reach the eardrum, they cause the membrane to vibrate. Those vibrations move through to the middle ear and stimulate three small bones there called ossicles, the malleus, the incus, and the stapes, in that order. They are commonly known as the hammer, anvil and stirrup because of their shape. The vibrations move through these bones and are then transmitted to the inner ear by applying pressure to the membrane covering the oval-shaped area.
The ossicles concentrate the vibrations on the membrane. The middle ear is air-based while the inner ear is liquid-based, so the ossicles serve as a buffer between these two areas. The middle ear muscles also help to dampen vibrations of very loud sounds so as not to damage the inner ear.
The cochlea is the main structure of the inner ear. It is a liquid-filled, coiled tube-like structure which is split into two halves: the scala tibuli and the scala timpani. There is a cochlear partition between the two structures, and this is what transforms vibrations into electrical signals.
In the cochlear partition is the organ of corti, which contains cilia, or hair cells, that are stimulated by sound waves through yet another set of membranes. They convert this stimulation into electricity through transduction, a process by which a biological cell converts one kind of signal or stimulus into another. This is what is ultimately received and interpreted by the brain.
The brain then uses the electrical signals from the cochlea to deduce the location and likely origin of the sound. Different parts of the brain, including the posterior and anterior belts of the cortex, and the temporal lobe, help to establish where a sound is coming from and what might be creating it.
Causes and Factors of Presbycusis Include Hereditary and Environmental Components
Presbycusis is the damaging or deterioration of one or more of the major components of the human auditory system. There are myriad causes for age-related hearing loss, and it is virtually impossible to tell with exact certainty what the specific causes of presbycusis are in any one individual. However, researchers have established that causes and factors include both hereditary and environmental components.
Hereditary components would obviously include genetic factors that might make an individual predisposed for a greater likelihood of experiencing age-related hearing loss. Geneticists are constantly performing exploratory research to better understand the effects that different genes have on human health factors, but they have not yet mapped the causal relationships comprehensively. As such, the body of knowledge around genetic predisposition for hearing loss — and the wisdom the medical community would need to predict such circumstances — is still early in its development.
Environmental factors for hearing loss, however, are generally easier to identify and connect. The most common environmental causes of hearing loss are chronic or episodic exposure to very loud sounds which can damage the eardrum, the cochlea, and other parts of the hearing system.
Factors Causally Related to Presbycusis Include Diabetes or Heart Disease
However, other factors have also been shown to be causally related to presbycusis, including health conditions like diabetes or heart disease, regular ingestion of certain pharmaceuticals, chronic infections, and habitual smoking.
Additionally, White/Caucasian individuals and persons of lower income levels are more likely to experience presbycusis. It isn’t entirely clear why race or income is linked to hearing loss, but one potential cause could be that a lot of lower-paying jobs expose workers to a lot more noise (construction, manufacturing, mining) and so there may be an indirect link from exposure to loud sounds.
Presbycusis can be a frustrating condition. Depending on the severity, it can affect basic life functions such as human discourse. For people with presbycusis, it’s common for a speaker’s voice to sound muffled or slurred, sometimes to the point of being incomprehensible.
Also, people with age-related hearing loss have a harder time hearing higher pitched sounds than lower pitched sounds. As a result, they often have more trouble hearing women’s voices than men’s since women’s voices tend to be higher in pitch.
Additionally, because of the lack of sensitivity to discern fine details in sound, background noises can make it particularly difficult for people with presbycusis to make out verbal communication. Finally, presbycusis may also be accompanied by tinnitus, a ringing in the ears that can vary in intensity among sufferers; tinnitus can make it very difficult to interpret and focus on real sounds coming from the environment.
Presbycusis Is a Major Concern for the Aging Population
Presbycusis is a major concern for the aging population. But aside from avoiding loud noise environments, there is not a lot at present that can be done to prevent the onset of presbycusis. And although there are treatments available, medical science and technology have not yet found cures.
Hearing aids are currently the most common treatment to counter the limitations of hearing loss. But this is more of a “band aid” on the problem than an actual cure. So research into preventions and cures for this condition should be among the highest medical priorities.
PSYC304 Perception, an undergraduate course in American Public University’s Psychology program, focuses on hearing impairments like presbycusis and other conditions that affect the ability to perceive the world. Visit the Psychology program webpage to learn more about the program.
About the Author
Dr. Gary Deel is a Faculty Director with the Wallace E. Boston School of Business at American Public University. He holds a J.D. in Law and a Ph.D. in Hospitality/Business Management. Gary teaches human resources and employment law classes for American Public University, the University of Central Florida, Colorado State University and others.
